Work Hardening Sintered Materials—A Metallographic Study

Abstract

Sintered alloy steels generally have a heterogeneous structure. Austenite may, in some cases, be present at room temperature. The work reported shows that the action of cold work causes the transformation of metastable austenite to martensite and that a big increase in hardness results. Sintered steels used in bearing applications make use of the transformation phenomenon; an initial ‘bedding in’ period being followed by a high resistance to further wear. It is shown that a 4% nickel composition has a good ratio of initial to final hardness. Higher alloy contents are less effective because the austenite produced on cooling from the sintering temperature is too stable to transform readily.