HIGH PERFORMANCE CARBURIZING STAINLESS STEEL FOR HIGH TEMPERATURE USE

摘要

A high performance stainless steel alloy component for high temperature service and method of production is provided in a ferrous alloy containing 0.05 to 0.50 wt. % C and 10 to 20 wt. % Cr. The shaped component, in the form of a high performance bearing, cam, gear or fastener, is carburized to achieve a carbon content of greater than 1.5 wt. % and preferably 2.0 to 2.5 wt. % in the case surface. The carburized component is then thermally treated by austenitizing, cooling, sub-zero cooling, tempering, followed by one or more cryogenic treatments followed by tempering. The microstructure of the component includes: (a) a working surface or case consisting predominantly of a martensitic matrix containing a large volume fraction of fine alloy carbides exhibiting high hardness and fatigue resistance, (b) a subjacent intermediate layer consisting substantially entirely of a stable, highly alloyed austenite, and (c) a core of a predominantly low carbon martensitic microstructure having a hardness higher than the intermediate layer and lower than the hardness of the working surface. The carburized and heat treated component combines hot hardness, wear resistance and corrosion resistance, particularly in a rolling bearing surface while retaining ductility, high fracture toughness and strength in the core.