Solid solutions in sputter-deposits of iron with 0 to 5 Wt Pct C
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AND
M.D.
MERZ
Supersaturated iron-carbon solid solutions containing 0.06, 0.18, 0.66, 2, 3, and 5 wt pct C were produced by sputter-deposition at 6~ to 21~ Homogeneous deposits of the same carbon composition as the multiphase source materials were produced by high rate (up to 0.0004 in. per hr) sputtering techniques and were 0.005 to 0.027 in. thick. The microhardnesses of the deposits were higher than the hardnesses of martensite with the same carbon content. The hardness increased rapidly from 680 Dph for 0.06 wt pct C content to an unusually high maximum of 1240 Dph at 2 wt pct C and then decreased slowly to 920 Dph at 5 wt pct C. The 0.06, 0.18, and 0.66 wt pct C deposits were bcc, and the 2 and 3 wt pct C deposits were bct. The tetragonality of the 5 wt pct C deposit was detected only after tempering at 150~ Lattice parameter c/a ratios for the tetragonal deposits were lower than expected from extrapolated martensite data, and they corresponded to the equation c/a = 1.006 + 0.019 (wt pct C). Nevertheless, the c/a ratio of I.i0 for 5 wt pct C deposit was higher than previously observed for martensite. No evidence of a martensitic transformation was found in the microstructures, which typically consisted of 0.5 to 1.0 /i diam columnar grains. Hardness data from tempered deposit samples and the lack of tetragonality of the low carbon deposits indicated that autotempering occurred during sputter-deposition.
T H E objective of this work was to investigate the properties of Fe-C alloys prepared by sputter-deposition at 6~ to 21~C. Advanced high-rate sputtering technology developed by E. D. McClanahan x'z was used to produce relatively thick deposits at rates from 0.0001 to 0.0004 in. per hr. The deposits were 0.005 to 0.027 in. thick, and contained 0.06, 0.18, 0.66, 2, 3, and 5 wt pct C. The results of our investigation were compared with current theories on martensite because the ironcarbon sputter-deposits were found to have many of the characteristics of martensite. Supersaturated solid solutions have been produced by rapid quenching of solids, liquids, and vapors, but only solid and liquid quenching have been reported for Fe-C alloys. Specifically, metastable body-centered-cubic (bcc) and body-centered-tetragonal (bct) solid solutions (martensite) containing up to about 2 wt pct C have been produced by quenching the solid austenite phase. 3 Ruhl and Cohen~ splat-quenched liquid Fe-C alloys and obtained austenite and martensite in the same proportions as found in quenched austenite of 1 to 2 wt pct C. Various mixtures of phases, including metastable epsilon phase, austenite, and cementite, were found in splat-quenched alloys of higher carbon concentrations. Evaporated S and sputtered 6 metal vapors have been quenched to form supersaturated solid solutions, but to our knowledge these methods have not been used to form supersaturated ironcarbon solid solutions. Stainless steels ~'2'7'8 and AISI-01 steel 9 were sputter-deposited without producing supersaturated solid solutions. The hardness of martensite increas
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