ABSTRACT
The austentic stainless steels now used for various industries are comparatively soft materials, and this is expected to cause problems in the future when these stainless steels are used in applications requiring high proof strength and the ability to withstand severe wear conditions. As a counter measure, it is effective to treat the surface of stainless steels, for example, by nitriding or carburising. Research targeting increases in hardness and wear resistant properties in the field of plasma heat treatment has been underway since 1980. The plasma-nitriding processing of stainless steels for increasing hardness and corrosion resistance has been reported to be successful. The reports focussed on the M4N, (Fe,Cr,Ni)4N, (Fe,Cr,Ni,Mo)2N1−x type of S phase and compounds.
In this study we have investigated the corrosion resistance and wear properties of a series of stainless steels having the S phase. Immersion tests were conducted in aqua regia and potentiometric measurements were made in 0.1N H2SO4 solutions. A ball-on-disc type wear test machine was used for the wear test.
S phase in aqua regia showed poorer corrosion resistance than the substrate, and the current density in passive potentials in 0.1N H2SO4 solutions was a little higher than that of the substrates. Wear loss of the S phase in sliding tests was less than that of the substrate, but the S phase had a significantly shorter sliding failure distance (200 m) than that of the specimens plasma-nitrided at 723 K (600 m).
