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The refractory nature and high ductility of body centered cubic (bcc) phase tantalum makes it a suitable material for corrosion‐ and wear‐resistant coatings on surfaces that are subjected to high stresses and harsh chemical and erosive environments. Sputter deposition can produce thick tantalum films but is prone to forming the brittle tetragonal beta phase of this material. Efforts aimed at forming thick bcc phase tantalum coatings in both flat plate and cylindrical geometries by high‐rate triode sputtering methods are discussed. In addition to substrate temperature, the bcc‐to‐beta phase ratio in sputtered tantalum coatings is shown to be sensitive to other substrate surface effects.

Studies of 50–200 eV Kr+ ion removal rates of niobium with a triode discharge system were conducted. A comparison was made of the removal rates of sputter‐deposited material removed during high‐rate sputter deposition and during ion bombardment after deposition. The removal rate of wrought niobium was also measured under similar plasma conditions for comparison. The results indicated that the removal rates were not affected by conditions of deposition and depended only on the energy of bombarding Kr+ ions, and were nearly the same for sputter deposited and wrought niobium. The results are discussed in terms of the neutral Kr atoms reflected from the target, Kr+ ions incident on the niobium substrates, and crystallographic texture of the niobium being bombarded.

Deposits of 5 to 500 μm thick coating were produced at rates from 0.025 to 2.5 μm/min on Al, Cu, Fe, and Kapton substrates in a triode system. Sputter parameters were as follows: Kr gas pressure (0.27–0.44 Pa), substrate temperature (21–184 °C), target voltage (300–2000 V), substrate bias (−35 to −100 V), ion current density (60 to 120 A/m2). A minimum substrate temperature of 100 °C was necessary to fully stabilize the fcc structure in the deposits. Chemical analyses and energy dispersive spectroscopy indicated that deposits, under certain conditions, contained substantially less Ga than the target. The loss of Ga was controlled by increasing the substrate temperature above 180 °C. The angular distribution of Pu and Ga sputtered under normal Kr+ ion impingement on a flat polycrystalline target was also measured. The Pu distribution was found to be ‘‘under cosine’’ for 300 eV ions and ‘‘cosine’’ for 900 eV ions. The Ga atom distribution showed a wide variation at different angles (normal to the target) depending upon conditions. At 0° the ratio of Ga to Pu was higher than in the target.

The triode sputtering technique and a split Cu-Ti target arrangement have been used to produce metastable extended solid solutions and amorphous phases in the Cu-Ti system. Metastable extension of the solid solubility of Ti in Cu-based fcc solid solution of up to 30 at. pct was observed; nearly 20 at. pct of Cu was incorporated metastably into the hcp solid solution based on Ti. Amorphous phase formation was observed in alloys containing approximately between 26 and 84 at. pct Ti. Amorphous deposits were as thick as 250 μm, without the presence of detectable crystalline phases. Interatomic spacings in both crystalline and amorphous alloys were found to follow an approximately linear trend with composition. Microhardness measurements indicated a very substantial increase in hardness in all alloys when compared with an extrapolated linear trend between pure Cu and Ti.

High concentrations of inert gases can be incorporated into the structure of certain bias‐sputtered rare earth/transition metal alloys, and these materials are useful as stable reservoirs of inert gas. Ni–La alloys containing a composition gradient ranging from about 0.3 to 30 at.% La have been deposited at several bias voltages, in a dc triode system, with cylindrical target–substrate geometry, using an asymmetric composite target, and a Kr discharge. The dependence of Kr content and alloy structure on composition (La/Ni atom ratio) and substrate bias has been determined systematically. Deposit structure was examined by x‐ray diffraction, and Kr content was measured by energy dispersive x‐ray spectroscopy and by vacuum fusion. At constant bias, Kr content initially increases rapidly with La/Ni, then saturates. As La/Ni ratio increases, alloy structure changes from fully crystalline to fully amorphous. Bias has a pronounced effect on preferred orientation and on relative fraction of crystalline phase. The...

Deposits of 304L stainless steel from 0.002–0.064 in. thick were produced at rates from 0.002–0.00075 in./h by triode sputtering techniques. Substrates were maintained at temperatures from 1 °–800 °C. The 304L, alloy was found to be removed by krypton atoms at a rate of 4.6 g/A-h (22 atoms/ion) with the target at 1509 V. The 0.064-in-thick sample produced on a substrate held at 1 °C showed a variation in columnar grain microstructure through the deposit thickness. Chemical analysis showed that the alloy composition of the deposits was nearly the same as the target. The data indicated that the deposits had slightly more chromium, but less nitrogen and carbon than the target. Electron microprobe data indicated the deposits were uniform in chromium and nickel concentrations. The deposit appearance, microstructure, and crystal structure were strongly dependent on substrate temperature. The deposits had dull surfaces, columnar grain microstructures, and body-centered cubic (bcc) crystal structure for substrate temperatures below about 360 °C. Between 360 ° and 500 °C the surfaces had mirror finishes, the grains were equiaxed, and the deposits consisted of a mixture of face-centered cubic (fcc) and bcc phases; at 500 °C the deposit was essentially all fcc. At 800 °C the deposit had a mirror finish, the grains were columnar, and the crystal structure was fcc.

Sputtering yields of water‐cooled two‐phase Ag–Ni and Ag–Co targets were found to be much lower than predicted by averaging the yields of the unalloyed metals. The target yields steadily decreased when the Ni or Co content increased from 0 to 30 at. %. Above 30‐at. % Ni or Co, the yields did not change and were equal to the respective yields for Ni and Co. Thus, the results indicate that yields may be predictable for some multiphase targets from the yield of the low‐yield phase. The unusually low yields were attributed to coating of the high‐yield Ag phase with lower‐yield Ni or Co during sputtering. Simultaneous coating and sputtering processes reached steady state before removal of 20 μ from freshly prepared non‐presputtered Ag–Ni targets even though Ni particles were up to 130 μ in diameter. Quantitative microprobe analysis of one Ag–Ni deposit indicated deposit compositions were nearly the same as target compositions.

Deposits of copper up to 1 mm thick were formed at room temperature in a triode sputtering apparatus using a krypton discharge under various conditions of sputtering rate, gas purity, and substrate bias. Room‐temperature recrystallization and grain growth displaying no twins were observed within 9 h after removal from the sputtering apparatus. This resulted in a dominant orientation of {100} planes parallel to the substrate‐deposit interface. Recrystallization rate increased as a function of increasing deposition rate, gas purity, and substrate bias. It was hypothesized that high intrinsic stress levels in the deposit provided both vacancies and the driving force for their diffusion to grain boundaries. Grain boundaries composed of {100} planes then adsorbed vacancies and moved by a combination of climb and glide. This movement was made possible by the elimination of barrier impurities, primarily oxygen, with the negative bias applied to the substrate during sputtering.

Several thick dc‐sputtered pure‐chromium deposits were examined for variations in hardness, crystallographic orientation, and microstructure as a function of substrate bias and deposition temperature. Deposit hardness increased to a maximum of approximately 700 DPH at −50 V substrate bias and then decreased for higher bias. Hardness also decreased with increasing deposition temperature. Bias had no effect on orientation but increasing temperature favored random rather than highly textured orientation. Microstructure changes corresponding to hardness changes were observed. Some tensile ductility was noted in a 400 °C deposit sputtered using a −50 bias.

The triode sputtering technique and a “split-target” arrangement were used to produce metastable crystalline and amorphous phases in the Cu-W system under essentially oxygen-free conditions. Large metastable extensions of solid solubility were observed both from the Cu (fcc) and W (bcc) sides of the phase diagram, and a wide range of metallic glass formation was observed, approximately between 30 and 65 at.% W. The thickness of the amorphous Cu-W phase (40–160 pm) that can be deposited without the formation of the metastable bcc phase appears to be dependent on the Cu-W alloy composition. On heating, the crystallization temperature of the amorphous alloys was higher than 350°C. The behavior of the lattice parameter and near-neighbor distance has been studied with x-ray diffraction, showing small positive deviations from an assumed Vegard's Law. Hardness measurements indicate that the metastable crystalline phases are relatively harder than the amorphous phase.

Gas turbines operated in the marine environment are limited in life and performance by sulfidation or hot-corrosion. Protective coatings deposited by sputtering appear to have the potential of significantly increasing engine life over that obtained with current coatings produced by other techniques. The sputtering process and its application to coating hot section components is the subject of this paper. Two programs are described. In one, metallic overlay coatings of the CoCrAlY type were deposited by dc triode sputtering. Deposition conditions were determined which resulted in adherent, crack-free coatings with a fine grained structure. Platinum diffusion barrier layers were also investigated. Sputtering apparatus suitable for coating turbine blades and vanes was constructed. The other program utilized supported discharge radio frequency sputtering to deposit zirconia coatings, which were intended to serve a thermal barrier function as well as a corrosion resistant one. Graded composition interlayers were investigated as a means of improving the compatibility of the zirconia coating with superalloys.Copyright © 1974 by ASME

Of the several radioactive inert gas isotopes generated by the fission process in nuclear reactor fuels, only Kr-85 has a long enough half-life (10.73 years) to be considered for long term storage. Kr-85 decays to Rb-85 releasing a beta particle with a maximum energy of 0.66 MeV and a very low flux of 0.52 MeV gamma rays. The chemical inertness of this isotope reduces markedly the biological effects of the gas but contributes to its long lifetime as a component of the earth’s atmosphere. In the past, the small quantities of Kr-85 generated and subsequently released from the fuel have been dispersed in the atmosphere, but federal regulations to take effect in 1983 limit the release to 50,000 Ci/gigawatt-yr of electrical power generated by a nuclear reactor (1). This amount is about 15% of that generated in a typical light water reactor (LWR) fuel. To meet this requirement, studies are underway to develop methods of separating the Kr from other reactor gases and storing it for periods of about 100 years until decay is largely complete.