ISSN:
1573-4889
Keywords:
inhibition
;
sulfur effects
;
carburization
;
Fe-Ni-Cr alloys
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Several commercial and laboratory-cast model austenitic alloys have been exposed in both sulfur-free carburizing environments and also in carburizing atmospheres to which additions of H2S have been made. These studies were concentrated over the temperature range 1223–1323 K at a fixed carbon activity (ac=0.8) with sulfur activities ranging from 2.2×10−12 bar to 1.4×10−9 bar. Under conditions of sulfur adsorption, e.g., $${\text{p}}_{S_{\text{2}} } $$ ≤ 5.5 × 10−11 bar at 1273 K, the blocking of adsorption sites for methane resulted in a transition from the parabolic kinetics observed during sulfur-free carburization to surface controlled linear kinetics. Higher levels of H2S promoted the formation of a surface layer of chromium sulfide which reduced internal carburization but became a problem itself. The role of minor alloying elements has been established and the use of thermodynamic phase stability diagrams in defining the optimum conditions for sulfur inhibition of carburization evaluated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00659340
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