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Nov 1972

Volume 9, Issue 6, pp. 1301-1474


An Examination of Electrode-Change Practice in Electroslag Melting

R. O. Jackson, A. Mitchell, and J. Luchok

J. Vac. Sci. Technol. 9, 1301 (1972); http://dx.doi.org/10.1116/1.1317026 (5 pages) | Cited 1 time

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An examination of the unsteady-state heat balanced of an ESR furnace during a power interruption has been made. The results of this study show that the ingot heat balance during an electrode change may be characterized by a single term, the volume fraction of liquid solidified during the interruption. The application of this term to ESR and VAR practice is demonstrated. The structure and composition of ingot metal solidified during this change can be related to the local temperature gradients and solidification rate during the change. In turn, this may be related to the steady-state liquidus isotherm and the volume fraction solidified. The role of the local segregation coefficient in determining the maximum tolerable electrode change time is clearly demonstrated by the above parameters. The general relation of the above mechanisms to the electrode-change method is discussed for some practical cases. The engineering and economic problems associated with electrode-change practice are detailed. It is concluded that although there are many instances where a properly engineered electrode-change method may be used with no adverse effects in the ingot, the general applicability of the method is in doubt.
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81.20.-n Methods of materials synthesis and materials processing
07.20.Hy Furnaces; heaters

Vacuum Duplexing—A Fresh Look at Existing Melting Techniques

R. S. Cremisio and R. W. Hornbaker

J. Vac. Sci. Technol. 9, 1306 (1972); http://dx.doi.org/10.1116/1.1317027 (9 pages)

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Changing technology patterns, coupled with growing demands for high product reliability at low cost, will result in a pronounced growth in the preparation of alloy grades subject to some form of vacuum melting of iron, nickel, and cobalt base alloys in the next 10 years. It is predicted that all grades slated for high reliability and∕or performance products will see some form of vacuum processing, whether degassing or primary melting. A trend towards duplexing of various melting methods into “melting systems” consisting of two or more melting methods is also developing for the same reason. The paper describes various iron, nickel, and cobalt base alloy systems and several product applications along with the characteristic problems thereof. A complete description of all known melting schemes is presented along with their specific characteristics relating to charge material, tendency for contamination, and applications to a full range of prevalent forms. The paper further describes unique combinations (duplexing) of these various methods in such a way as to result in optimized quality and melting cost. Application to specific problems known in the melting industry will be discussed. Recommendations for maximizing productivity at lowest cost through duplexing will be made.
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81.20.-n Methods of materials synthesis and materials processing
81.05.Bx Metals, semimetals, and alloys

Importance of Arc Gap Control in Vacuum Consumable Arc Remelting of Superalloys

G. R. Mumau and W. B. Aufderhaar

J. Vac. Sci. Technol. 9, 1315 (1972); http://dx.doi.org/10.1116/1.1317028 (3 pages)

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In vacuum consumable arc remelting, control over the ingot solidification rate is of paramount importance to optimum product quality. In general, solidification rate is very dependent upon ingot size and melting current which help to define the general characteristics of the molten pool geometry and that of the advancing freezing front within the ingot. However, control of these parameters is achieved by precisely monitoring arc gap throughout the melting operation. By having a close control over the arc gap, the vacuum melter can eliminate variations in solidification rate which can cause localized harmful segregates. There are several types of controls used in the vacuum melting industry today and these are discussed, including the hash control used at Special Metals Corporation. The important features of the control are outlined with respect to their influence on arc gap, including speed of feed, voltage limitation, and basic hash∕arc gap relationships. The importance of controlling the arc gap in Udimet 718 is shown by illustrating the effect of intentional controlled variations in arc gap at several melting currents on the formation of several types of segregates. The method of programming arc melt cycles to gain the most control over arc gap to ensure a reproducible, high quality product is discussed.
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81.20.-n Methods of materials synthesis and materials processing
81.30.Fb Solidification
81.05.Bx Metals, semimetals, and alloys

The Reactions of Titanium and Silicon with Al2O3-CaO-CaF2 Slags in the ESR Process

G. Pateisky, H. Biele, and H. J. Fleischer

J. Vac. Sci. Technol. 9, 1318 (1972); http://dx.doi.org/10.1116/1.1317029 (4 pages)

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The reactions of titanium and silicon with slags of the system alumina-calcium oxide-fluorspar were calculated. The calculations were confirmed by melts in a laboratory induction furnace and also through statistical calculations of 320 heats of 500 mm □ (3,6 ton) ingots for the Ti–Al2O3 reaction and of 100 ESR heats of the same ingot size for the Si–Al2O3 reaction. By statistical evaluation of all heats the dependence of the aluminum and titanium or silicon contents for different TiO2 or SiO2 contents of the slags were determined. By application of these data the losses of Ti or Si by a reaction with alumina can be prevented.
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81.20.-n Methods of materials synthesis and materials processing
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

The Current Status of the VOD∕LD–VAC Process

Hans J. Fleischer

J. Vac. Sci. Technol. 9, 1322 (1972); http://dx.doi.org/10.1116/1.1317030 (4 pages)

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Presented by C. W. Finkl
A. Finkl and Sons Company, subsidiary Republic Steel Company
The vacuum decarburization of high chromium heats called VOD in North America and LD–VAC in the rest of the world has revolutionized the melting practice of stainless steel. Since production trials started at the end of the last decade, a world production capacity of 1 720 000 tons annually has been built or is under construction. This paper deals with the latest design of the Vacuum Decarburizing Unit, and of the basic-lined slide gate ladles. It sequentially describes operating procedures giving time, chemistry, and temperatures related to the separate steps of the process. Multicombinations of melting and vacuum decarburizing facilities are explained along with cost and furnace time savings. Equipment descriptions cover cost and type of ladle refractories, vacuum pumping curve, inherent fume control, and end-point determination. Latest metallurgical developments and short cycle desulfurization in direct combination with decarburization outside the premelting furnace are also discussed, as is the advantage of vacuum ladle degassing in the VOD∕LD–VAC unit.
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81.20.-n Methods of materials synthesis and materials processing

The Effect of C and N on the Properties of Fe–Cr–Mo Ferritic Stainless Steels

A. P. Bond and R. F. Steigerwald

J. Vac. Sci. Technol. 9, 1326 (1972); http://dx.doi.org/10.1116/1.1317031 (1 page)

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The effect that C and N contents have on the toughness of Fe–Cr–Mo alloys has been known for some time, but only recently have vacuum melting and inert-gas or inert-gas-vacuum combination refining process between developed to the point where low interstitial ferritic stainless steels are commercially attractive engineering materials. This paper reviews the effects of C and N contents on various properties of Fe–Cr–Mo alloys in which the interstitial level varies over the range 50–1000 ppm. The alloys are divided into two classes: 25Cr–Mo and 18Cr–Mo. The properties studied included toughness, welded ductility, resistance to intergranular corrosion, and resistance to pitting corrosion. Some of the higher Mo alloys presented interesting problems since heat treatments used to negate the effects of carbide and nitride precipitation produced undesirable phases. This problem could be avoided in the higher purity alloys by using high temperature annealing treatments. The amount of C and N that can be tolerated before these ferritic stainless steels become susceptible to intergranular corrosion after welding is a function of their Mo and Cr contents with the more highly alloyed material having the higher limits. Both Ti and Nb can be used to stabilize less pure steels against intergranular corrosion, but both C and N must be considered in determining the proper addition. Although stabilizing additions appear to improve the as-welded ductility of less pure Fe-Cr-Mo alloys, they do not improve their annealed toughness. Generally speaking, purer alloys have better resistance to pitting corrosion.
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81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.05.Bx Metals, semimetals, and alloys

Improved M50 Aircraft Bearing Steel through Advanced Vacuum Melting Processes

R. Schlatter and J. P. Stroup

J. Vac. Sci. Technol. 9, 1326 (1972); http://dx.doi.org/10.1116/1.1317032 (8 pages) | Cited 1 time

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A brief review of the vacuum metallurgical processes used for the production of high performance aircraft bearing steels is presented. Primary vacuum induction melting of M50 bearing steel in the Therm-I-Vac furnace and subsequent vacuum arc remelting has brought about a two- to threefold improvement in rolling contact fatigue life which appears to be related to precise composition control and very low gas and inclusion contents. Extensive vacuum-carbon deoxidation by an active boil and resultant more stable vacuum arc remelting conditions have been found to be important factors in producing a superior quality consumable ingot with a uniform structure free of macro-segregations. Property improvements in regard to product consistency, structural uniformity, and microcleanliness as well as the evaluation of bearing materials by rolling contact fatigue testing are discussed. It is believed that the significantly better rolling contact fatigue lives achieved by an optimized TIV+VAR practice are basically due to marked reductions of (1) interstitial gas content (H, O, N), (2) nonmetallic (S) and metallic impurities, (3) total inclusion content.
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81.05.Bx Metals, semimetals, and alloys
81.20.-n Methods of materials synthesis and materials processing

The Feasibility of Producing Superalloy Electroslag Remelted Hollows

H. J. Klein

J. Vac. Sci. Technol. 9, 1334 (1972); http://dx.doi.org/10.1116/1.1317033 (6 pages)

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The feasibility of producing electroslag remelted hollows is shown. In this work electroslag hollows of two superalloys, Hastelloy alloy X and Haynes alloy No. 718 were produced. The microstructure of the as-cast hollows was significantly finer than that of a comparable ESR solid ingot. The segregation ratio defined as the maximum concentration of an element divided by the minimum concentration of the element was 1.16 and 1.33 for molybdenum for the ESR hollow and solid ingot, respectively. Mechanical property results from ring rolled and cross rolled specimens indicated that wrought properties were achieved in both alloys when total reductions exceeded 43%–50%. An acceptable although not optimum microstructure was obtained, and the reasons for this are discussed.
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81.10.Fq Growth from melts; zone melting and refining
81.05.Bx Metals, semimetals, and alloys
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

The Role of Inclusions on Mechanical Properties in High Strength Steels

J. J. Hauser, M. G. H. Wells, and I. Perlmutter

J. Vac. Sci. Technol. 9, 1339 (1972); http://dx.doi.org/10.1116/1.1317034 (1 page)

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The relationship between quantity and type of nonmetallic inclusions and critical mechanical properties was determined for the high-strength steels 4340 and 300M. Quantitative television microscope scanning data and various petrographic and microprobe methods were used to study the inclusions. Inclusion statistics showed that improved cleanliness was obtained in ascending order of (1) electric furnace air melted, (2) Dortmund–Horder degassed, (3) vacuum-arc–remelted and (4) electron beam hearth refined steels. Studies in the electron beam melted material were made on 1000 lb heats, whereas the remaining data were obtained on large-scale production heats. The properties for both 4340 and 300M improved in a similar manner with cleanliness. Transverse reduction of area was the property most influencd by inclusion content. Fatigue and impact properties were also affected, though to a lesser degree. Plane strain fracture toughness was relatively little affected by inclusion content and, in fact, longitudinal and transverse properties were substantially the same in direct contrast to reduction of area, impact, and fatigue properties. KIc is thus not a meaningful parameter for quality control measurement in these high-strength structural steels. While we realize that other factors, such as microsegregation, affect properties, we conclude that for steels processed according to specified practices, the inclusion content is the most important variable influencing critical mechanical properties.
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81.05.Bx Metals, semimetals, and alloys
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
61.72.Qq Microscopic defects (voids, inclusions, etc.)

A Discussion of the Paper “The Role of Inclusions on Mechanical Properties in High-Strength Steels”

L. F. Porter

J. Vac. Sci. Technol. 9, 1340 (1972); http://dx.doi.org/10.1116/1.1317035 (4 pages)

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The authors show that at high tensile strength fracture toughness is insensitive to steel cleanliness, and reduction of area is very sensitive to steel cleanliness. These conclusions are generally substantiated by work conducted at U. S. Steel. The U. S. Steel work amplifies that reported in the subject paper by examining the effect of residual elements (cleanliness) on the reduction of area and fracture toughness of 18Ni maraging steels and the effect of prior-austenite grain size and residual-element content on the reduction of area and fracture toughness of high-strength quenched and tempered alloy steels. The U. S. Steel work shows that for the maraging and alloy steels studied, reduction-of-area values are very sensitive to residual-element level but not affected much by tensile-strength levels in the range 230–300 ksi. The fracture toughness of the maraging steels shows a sensitivity to residual-element level that decreases as the strength is raised. The steels appear to reach a point of complete insensitivity to residual-element level at a tensile strength of 310 ksi. At this strength, the fracture toughness approaches a KIc value of 50 ksi( in.)½. The fracture toughness of the alloy steels is insensitive to residual-element level throughout the tensile-strength range 230–320 ksi, but is sensitive to prior-austenite grain size. The grain-size sensitivity decreases as the strength level increases and appears to reach a point of complete insensitivity at a tensile strength of about 310 ksi. Again, the fracture toughness of the steels at a tensile strength of 310 ksi approaches a KIc value of approximately 50 ksi in.½. It is concluded that lowering residual-element levels by vacuum melting should improve the fracture toughness of maraging steels at tensile strengths below 310 ksi but will probably not improve the fracture toughness of quenched and tempered alloy steel at tensile strengths in the range 230 ksi and higher. Lowering residual elements by vacuum melting improves the ductility, as measured by reduction of area, of both maraging and alloy steels over the entire range of strengths studied. Reduction of area is not very sensitive to tensile strength in the range studied.
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81.05.Bx Metals, semimetals, and alloys
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
61.72.Qq Microscopic defects (voids, inclusions, etc.)

New Developments in Plasma Arc Melting

G. K. Bhat

J. Vac. Sci. Technol. 9, 1344 (1972); http://dx.doi.org/10.1116/1.1317036 (7 pages)

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Designs of plasma arc melting and plasma arc remelting systems available for metal refining, scrap recycling, cast structure improvement, and, in general, for the manufacture of very high quality ferrous and nonferrous metal alloys are reviewed. The advantages of plasma melting and remelting techniques in comparison to the various primary and secondary melting techniques are discussed. Data relative to the materials produced by this special melting technique are provided.
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81.20.-n Methods of materials synthesis and materials processing
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Vacuum Induction Melting of Titanium

N. M. Griesenauer, S. R. Lyon, and C. A. Alexander

J. Vac. Sci. Technol. 9, 1351 (1972); http://dx.doi.org/10.1116/1.1317037 (5 pages) | Cited 2 times

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Thermodynamic and melting experiments indicate considerable potential for the use of nonstoichiometric yttria as a crucible material for cold-wall induction melting of titanium metal. Experiments have shown that substoichiometric (reduced) Y2O3−x offers more resistance to attack by molten titanium, due to lower oxygen potential, but is subject to increased uptake of yttrium into solution. Yttria reacts with and contaminates molten titanium having greater than 100 °C superheat and where the crucible temperature is equal to or exceeds the melt temperature. The yttrium taken into solution, however, scavenges oxygen from the titanium solution and precipitates as Y2O3−x, reducing interstitials to acceptable levels. Normal cold-wail induction melting, using greater metal mass to contact area in a substoichiometric yttria crucible, should yield high quality titanium metal, comparable to some grades of present commercially pure metal. Development of the crucible material is continuing with studies of larger cold-wall induction melts.
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81.20.-n Methods of materials synthesis and materials processing
81.05.Bx Metals, semimetals, and alloys

Improved Melting and Casting Procedures for a Cobalt-Base Magnetic Alloy

D. P. Moak, W. H. Pfeifer, W. J. Hildebrand, P. J. Sewall, D. P. Cianelli, and G. L. King

J. Vac. Sci. Technol. 9, 1356 (1972); http://dx.doi.org/10.1116/1.1317038 (4 pages)

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One component of a very intricate central station telephone switching system contains a hard magnetic alloy of the composition cobalt-12 wt% iron-4 wt% gold. Problems were encountered during the final stages of the fabrication of the alloy to final form (0.00050 in.×0.0054 in. tape) and during subsequent assembly of this product. Extensive failure analyses were performed to identify the nature of the problems, and for the most part, the causative factors were traced to the induction melting and casting practices employed for initial synthesis of the alloy. The major problems addressed during the melting and casting research were inclusions and centerline porosity in the ingots prepared for subsequent fabrication. Since the most likely source of inclusions can be related to melting crucibles, sprues, runners, gates, etc., initial attention was directed toward these areas. Sprues, runners, and gates were eliminated, and high-density, stable crucible was employed. Massive copper molds were used and ceramic hot tops were eliminated. Although several molding variables were investigated, centerline porosity (secondary piping) was eliminated only by very controlled pouring rates to effect directional solidification. In conclusion some final yield data that relate to the improved vacuum melting and casting techniques developed are presented.
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81.10.Fq Growth from melts; zone melting and refining
75.50.Vv High coercivity materials

A Process for Delubrication, Presintering, Sintering, and Rapid Cooling in a Vacuum Induction Furnace

J. F. Hallemeier

J. Vac. Sci. Technol. 9, 1360 (1972); http://dx.doi.org/10.1116/1.1317039 (5 pages)

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Delubrication, presintering, and sintering are major steps in the manufacture of many products in the powder metallurgy field. The quality of the final product, to a great extent, depends on the quality, accuracy, and reliability of the sintering equipment used. The vacuum induction furnace for delubrication, presintering, sintering, and rapid cooling described below offers the possibility of delubricating the charge under vacuum and protective or reactive gas atmospheres at reduced pressures and to sinter the material in the same furnace, eliminating charge handling and transfer between the delubrication and sintering processes. All components of the furnace chamber and manifolds which come in contact with lubricant vapors are heated during the delubrication cycle and thus it is impossible to accumulate any traces of condensed wax in critical areas of the furnace. This eliminates the possibility that during sintering the charge is contaminated by lubricant decomposition products. The performance of the total cycle from delubrication to cooling in one furnace and the application of forced gas cooling improve the economic picture of the sintering process. Elaborate controls and programmers provide precise process control and generation of valuable records. The design of the furnace results in reduced maintenance and service costs.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
07.20.Hy Furnaces; heaters

Synthesis and Fabrication of High Purity Hafnium Nitride and Hafnium Carbide

R. L. Heestand

J. Vac. Sci. Technol. 9, 1365 (1972); http://dx.doi.org/10.1116/1.1317040 (3 pages) | Cited 1 time

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The procedures used to prepare kilogram quanties of hafnium nitride and hafnium carbide powders and hot-pressed billets are described. In order to maintain high purity, all steps of the process were conducted in either a vacuum or a high purity atmosphere. Analyses conducted on the starting materials and at various stages of processing indicated that target impurity levels, i.e., less than 100 ppm oxygen, could not be attained but that high levels of contamination could be avoided.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Freeze Drying: A Unique Approach to the Synthesis of Ultrafine Powders

F. K. Roehrig and T. R. Wright

J. Vac. Sci. Technol. 9, 1368 (1972); http://dx.doi.org/10.1116/1.1317041 (5 pages) | Cited 5 times

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The freeze-dry process and its application in the general area of inorganic materials synthesis will be discussed. Details of the process will be given as well as its capabilities for producing ultrafine powders such as Pb–10 v∕o MgO, WC, and W2C, ultrafine grained consolidated materials such as W–25 Re will be shown. Also, the application of the process for producing dispersion-strengthened systems such as Cu–ThO2 and Cu–W will be discussed.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Application Possibilities of Atomic Resonance Absorption Spectroscopy in Vacuum Metallurgy

E. I. Fazekas, M. Mezey, and R. F. Bunshah

J. Vac. Sci. Technol. 9, 1373 (1972); http://dx.doi.org/10.1116/1.1317042 (4 pages) | Cited 1 time

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Many of the processes in vacuum metallurgy involve the presence of one of the constituents in the vapor phase at pressures less than 1 atm, often less than 10−3 Torr. Recently, it has been shown that atomic resonance absorption spectroscopy can be used to detect very low partial pressures. Therefore, the possibility is open to use this technique to study and∕or control various vacuum metallurgical processes. This paper considers briefly the theoretical background, demonstrates the application of the principle, and discusses the possible applications in vacuum metallurgy.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.20.-n Methods of materials synthesis and materials processing

High Rate Ion Production for Vacuum Deposition

John R. Morley and Hugh R. Smith

J. Vac. Sci. Technol. 9, 1377 (1972); http://dx.doi.org/10.1116/1.1317043 (2 pages) | Cited 2 times

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A high current, low voltage magnetically confined and bent hot hollow cathode discharge was used to simultaneously evaporate and to ionize materials under vacuum. At power levels of about 15 kW, (60V, 250A) evaporation rates of 4 g∕min were observed for copper and quartz from a 3 in. diam water-cooled crucible. Two 6×6 in. substrates were mounted symmetrically 20 in. above the source one being at crucible (ground) potential, the other having a negative bias voltage (0–200 V) in order to collect ions. At a given evaporation rate, the biased substrate collected about twice as much copper and about five times the amount of quartz as that deposited upon the grounded substrate.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Vacuum Deposition of Alloys—Theoretical and Practical Considerations

James S. Foster and W. H. Pfeifer

J. Vac. Sci. Technol. 9, 1379 (1972); http://dx.doi.org/10.1116/1.1317044 (6 pages)

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The conditions necessary for successful steady-state vacuum deposition of a binary alloy from a single continuously fed source are examined and used to relate the compositions of the source and the deposit. This relationship involves the vapor pressures, atomic weights, activity coefficients, and weight percentages of the elements in the alloy. Extensions to prediction of the behavior of impurities and to ternary and higher order systems are discussed. The temperature sensitivities of single and multiple sources are qualitatively compared. A method of approximating the time required to reach steady state conditions is presented. Practical problems associated with the use of poor quality source materials are reviewed and recommendations are given for use in selecting source materials.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Activated Reactive Evaporation Process for High Rate Deposition of Compounds

R. F. Bunshah and A. C. Raghuram

J. Vac. Sci. Technol. 9, 1385 (1972); http://dx.doi.org/10.1116/1.1317045 (4 pages) | Cited 13 times

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Activated reactive evaporation is a new process developed for the high rate deposition of compounds. It circumvents problems associated with direct evaporation of compounds. Metal vapors from high rate evaporation sources are reacted with a gas in the vapor phase to form and deposit compounds. The vapor phase reaction has to be activated by ionization of the reacting species, i.e., metal vapor and gas in the reaction zone. The steps of compound synthesis and compound deposition are thus separated. Control of deposit stoichiometry, e.g., [C∕M] ratio for TiC synthesis is readily achieved by controlling the relative amounts of reactants. Results on the synthesis of carbides, oxides, and nitrides are presented.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

The Effect of Substrate Temperature on the Structure of Titanium Carbide Deposited by Activated Reactive Evaporation

A. C. Raghuram and R. F. Bunshah

J. Vac. Sci. Technol. 9, 1389 (1972); http://dx.doi.org/10.1116/1.1317046 (6 pages) | Cited 10 times

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A change in substrate temperature produces a marked change in the microstructure, preferred orientation, and microhardness of TiC deposits. At low temperatures (∼500 °C) the structure consists of tapered crystallites and changes to a structure consisting of columnar grains at the higher temperatures (∼1000 °C). The high temperature deposits exhibit very high microhardness values (∼4500–5000 kg∕mm2 KHN).
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

The Deposition of Multicomponent Phases by Ion Plating

Howard R. Harker and Russell J. Hill

J. Vac. Sci. Technol. 9, 1395 (1972); http://dx.doi.org/10.1116/1.1317047 (5 pages) | Cited 2 times

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Some preliminary results obtained using electron beam evaporation of multicomponent phases are presented. The combination of ion plating and the use of a rod-fed electron beam source allows coatings to be made with both alloy and compound materials on substrates which have been very difficult in the past. The results include both metallic and nonmetallic coatings on dielectric substrates.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating

Preparation and Corrosion Properties of a Tantalum Sputtered Thick Film

S. Kashu, T. Sano, and C. Hayashi

J. Vac. Sci. Technol. 9, 1399 (1972); http://dx.doi.org/10.1116/1.1317048 (5 pages)

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A tantalum sputtered film formed on the surface of stainless steel (AISI-316) has good corrosion resistance to hot sulphuric acid. Corrosion resistance of sputtered tantalum films, 6–20 μ thick is superior to that of other high quality corrosion resistant materials, such as niobium, titanium, zirconium, Hastelloy-B, and AISI-316 stainless steel. The corrosion rate of sputtered tantalum films is similar to that of 50 μ thick tantalum foil. Results of up to 1000 h corrosions tests, an adhesion strength test, and a bend test of the film are presented in this paper.
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81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering
81.65.Kn Corrosion protection

The Influence of Ion Bombardment on the Microstructure of Thick Deposits Produced by High Rate Physical Vapor Deposition Processes

R. F. Bunshah and R. S. Juntz

J. Vac. Sci. Technol. 9, 1404 (1972); http://dx.doi.org/10.1116/1.1317049 (2 pages) | Cited 8 times

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The structure of massive deposits produced by high rate physical vapor deposition processes above 0.3 Tm substrate temperature consists of columnar grains. The length and width of the columnar grains increases with substrate temperature. Ion bombardment of the deposit during deposition by biasing the substrate negatively to 5 kV produces a marked refinement in grain size. A possible mechanism is nucleation of new grains by localized temperature spikes at the vapor–solid interface due to ion bombardment.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.80.Jh Ion radiation effects
81.05.Bx Metals, semimetals, and alloys

Preparation of Alloy Deposits by Continuous Electron Beam Evaporation from a Single Rod-Fed Source

R. Nimmagadda, A. C. Raghuram, and R. F. Bunshah

J. Vac. Sci. Technol. 9, 1406 (1972); http://dx.doi.org/10.1116/1.1317050 (7 pages) | Cited 2 times

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A theoretical model is presented for the evaporation of an alloy of the desired composition from a single rod-fed electron beam heated vapor source. Experimental work on deposition of a Ni—20Cr alloy from such a source confirms the proposed model. At high evaporation temperatures, the times necessary for the pool to assume steady state composition are small, about 15 min, thus making the process economically attractive.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.Bx Metals, semimetals, and alloys

Electron Beam Float Zone Melting and Vacuum Degassing of Niobium Single Crystals

R. E. Reed

J. Vac. Sci. Technol. 9, 1413 (1972); http://dx.doi.org/10.1116/1.1317051 (6 pages) | Cited 3 times

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Niobium metal powder produced by electrodeposition from molten salts was electron beam float zone melted (EBFZM) for purification and growth of single crystals. It was necessary to EBFZM with a high oxygen partial pressure to reduce the carbon level. A high resistance ratio (R300 K∕R4.2 K(15 kG)=6500) and low flow stress (τly=460 gm∕mm2) was obtained after a high temperature anneal (2350 °C) in high vacuum (2×10−10 Torr). Extensive material characterization results are reported for the niobium at various stages in the purification process. The impurity content determined by chemical analyses did not correlate with the resistance ratios; however, the flow stress exhibited an excellent correlation with resistance ratio. These results imply that interstitial impurity in solid solution is the impurity distribution most affecting disslocation motion.
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81.10.Fq Growth from melts; zone melting and refining
81.20.Ym Purification
81.05.Bx Metals, semimetals, and alloys

Development and Evaluation of Materials for Vacuum Power Interrupters

E. A. Attia

J. Vac. Sci. Technol. 9, 1419 (1972); http://dx.doi.org/10.1116/1.1317052 (5 pages) | Cited 1 time

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In order to predict the interruption ability and residual gaseous environment after interruption in hermetically sealed vacuum power interrupters, experimental procedures were developed to measure gaseous contamination of the materials intended for contact application using dc arc induced vaporization and mass spectrometric analysis of the released gases. It was found that copper degassed by vacuum induction melting contains bulk residual gas compounds of carbon, oxygen, and hydrogen of concentration of about 0.08, 0.02, and 0.02 ppm-wt, respectively, and is capable of interrupting currents in the 10-kA range. The surface layer contains a much higher degree of contamination. CH4 (65%), CO (22%), and H2 (7%) are the major residual gases released during interruption.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Investigation of the Effect of Vacuum Environment on the Fatigue and Fracture Behavior of 7075–T6

C. Michael Hudson

J. Vac. Sci. Technol. 9, 1424 (1972); http://dx.doi.org/10.1116/1.1317053 (4 pages) | Cited 1 time

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Axial-load fatigue-life, fatigue-crack-propagation, and fracture-toughness experiments were conducted on sheet specimens made of 7075-T6 aluminum alloy. These experiments were conducted at air pressures ranging from 101kN∕m2 to 7 μN∕m2 to determine the effect of air pressure on fatigue behavior. Analysis of the results from the fatigue-life experiments indicated that for a given stress level, the lower the air pressure was the longer the fatigue life. At a pressure of 7 μN∕m2, fatigue lives were 15–30 times longer than at 101 kN∕m2. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue-crack-growth rates were approximately twice as high at atmospheric pressure as in vacuum. However, at higher values of stress-intensity range, the fatigue-crack-growth rates were nominally the same in vacuum and at atmospheric pressure. An empirical equation developed by Forman, Kearney, and Engle was fitted to the crack-propagation data using least-squares techniques. This equation gave an excellent fit to the data generated both in vacuum and at atmospheric pressure. Analysis of the fracture-toughness data showed there was essentially no difference between the fracture toughness of 7075-T6 in vacuum and at atmospheric pressure
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.05.Bx Metals, semimetals, and alloys
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)

Vacuum Heat Treating

W. C. Pine

J. Vac. Sci. Technol. 9, 1428 (1972); http://dx.doi.org/10.1116/1.1317054 (1 page)

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The use of vacuum equipment to heat treat materials to improve their physical characteristics is covered in this paper. Types of vacuum furnaces and their part in the heat treating of these materials is covered in depth. The newer methods of quenching brought about by the widening of the varieties of materials to be heat treated are also thoroughly discussed and reasons are given for the changes which have taken place. The use of a vacuum furnace in heat treating is not new, but during the past few years there has been more interest shown in this method than ever before with the inevitable increase in the number of facilities available. The first vacuum furnaces cooled materials from the austenitizing temperature by merely backfilling with an inert gas. Later a fan was added to increase the cooling rate and finally this was succeeded by a recirculator utilizing a heat exchanger and the movement of greater velocities of gas which resulted in the broadening of the number of materials that could be successfully vacuum heat treated. Later liquid quenching became available and the list of materials that could be vacuum heat treated was broadened even more. At about this time it became more and more apparent that hard vacuums were not required to successfully heat treat without changes in the surface chemistry of the materials. As a result, most heat treating is now carried out at pressures ranging from 20 to 150 μ rather than in the submicron range. It is concluded that the use of vacuum provides an excellent environment for the heat treatment of various materials even in some cases resulting in unusual wear resistance and greatly improved life.
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81.40.Gh Other heat and thermomechanical treatments
07.20.Hy Furnaces; heaters
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Investigation of Gas–Solid Reactions by Modulated Molecular Beam Mass Spectrometry

R. H. Jones, D. R. Olander, W. J. Siekhaus, and J. A. Schwarz

J. Vac. Sci. Technol. 9, 1429 (1972); http://dx.doi.org/10.1116/1.1317055 (13 pages) | Cited 25 times

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An apparatus for the study of gas-solid reactions which produce gaseous reaction products is described. The reactant gas contacts the solid as a molecular beam travelling in vacuum. Gaseous reaction products are monitored by a mass spectrometer as they are emitted from the surface. The technique relies heavily upon modulation of the molecular beam to improve the signal-to-noise ratio. In addition, chopping of the reactant beam induces modulation at the same frequency in the reaction products and the phase differences between these two signals contains important kinetic information. Methods of comparing theoretical models of the surface processes with the phase and amplitude information provided by the experiment are presented.
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34.50.Lf Chemical reactions
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
37.20.+j Atomic and molecular beam sources and techniques
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment

Rotary, Linear Motion Vacuum Feedthrough

Anthony DiGiallonardo, Raymond D. Dixon, and Kenneth L. Anderson

J. Vac. Sci. Technol. 9, 1442 (1972); http://dx.doi.org/10.1116/1.1317056 (1 page)

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This paper describes a rotary, linear motion feedthrough. This was designed and built to permit film deposition from a source located below the substrate and subsequent rotation by 180° and translation of 3 in. This combination of motions was required for the film deposition and subsequent movement of the substrate and thin film into position to form one plate of a vibrating capacitor.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Doping Characteristics of Flash-Evaporated Thin Film Gallium Arsenide

Ding Hua Hu and E. J. Charlson

J. Vac. Sci. Technol. 9, 1443 (1972); http://dx.doi.org/10.1116/1.1317057 (5 pages)

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Thin films of gallium arsenide were deposited on glass substrates by flash-evaporating the powder with an excess of pure arsenic. An independently controlled tin boat supplied the n-type dopant. Doping characteristics were evaluated by a metal-insulator-semiconductor (MIS) capacitance measurements and field effect conductivity modulation using a thin-film-transistor structure. Results showed that drift mobility for carriers in the space charge depletion region greater than 1 cm2∕V sec can be observed only for a narrow range of carrier concentrations. Surface state densities and surface carrier trapping was reduced by an indium alloy process.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ey III-V semiconductors
73.20.-r Electron states at surfaces and interfaces

Adsorbed CO2 Detection Using Attenuated Total Reflection

Donald B. Novotny

J. Vac. Sci. Technol. 9, 1447 (1972); http://dx.doi.org/10.1116/1.1317058 (5 pages) | Cited 1 time

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The use of the infrared attenuated total reflection technique (ATR) was explored as a sensitive procedure for the measurement of surface coverages of carbon dioxide films condensed on silicon. The technique of ATR appears to be feasible for the study of monolayer coverages. It was also demonstrated that the surface condensed CO2 molecule does not exhibit a rotation.
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81.70.Fy Nondestructive testing: optical methods
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

An Experimental System for a Study of the Kinetics of Heterogeneous Nucleation of Metals on Singal Crystal Mica Substrates

A. Grant Elliot

J. Vac. Sci. Technol. 9, 1451 (1972); http://dx.doi.org/10.1116/1.1317059 (6 pages)

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An ultrahigh vacuum LEED system has been modified for carrying out step kinetic nucleation studies. A substrate heating oven giving accurate, reproducible (±5 °C) surface temperatures, a condensate evaporation oven, a water-cooled quartz crystal microbalance, and a silicon monoxide evaporation source are described. Operating conditions and procedures leading to the attainment of number densities of nuclei reproducible to within a factor of two and nucleation rates accurate to within ±30% are discussed.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
64.60.Q- Nucleation

The Measurement of Conductance to Free Molecular Flow by Substitution Procedures

S. Ruthberg

J. Vac. Sci. Technol. 9, 1457 (1972); http://dx.doi.org/10.1116/1.1317060 (13 pages)

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A method is presented which yields an order of magnitude increase in precision in the measurement of conductance to free molecular flow. The technique utilizes a calibrated variable conductance as a reference in a true substitution procedure. A series line was used to study balanced and unbalanced conditions and to explore the effects of various factors on precision, such as flow stability, pump behavior, ionization gauge sensitivity and response, temperature, transients, and sorption. A parallel line was used for measurements on short tubes of small diameter. For this, an iteration technique was employed for the calibration of the variable conductance on an absolute basis. Ionization gauge resolution of 0.02% and linearity of better than 0.1% were achieved. Relaxation effects were apparent. Conductance measurement precision of a few parts per 1000 was obtained. Transmission probabilities for the small diameter, short tubes showed deviations of as much as 18% from the Clausing factors at length-to-radius ratios ≥1, but approached the Clausing values as l∕r→ 0. Deviations of <1% from the Clausing value required l∕r ≤0.05.
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47.45.Dt Free molecular flows

Physisorption of Argon on Pyrex at Low Pressures

J. Shien-Chung Jen and J. Pinckney Wightman

J. Vac. Sci. Technol. 9, 1470 (1972); http://dx.doi.org/10.1116/1.1317061 (2 pages) | Cited 2 times

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Abstract Unavailable
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

The Effects of Temperature on the Accuracy of Crystal Oscillator Thickness Monitors

W. A. Porter and Stephen W. Anderson

J. Vac. Sci. Technol. 9, 1472 (1972); http://dx.doi.org/10.1116/1.1317062 (3 pages)

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Abstract Unavailable
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
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