Influence of microstructure on impact and wear behaviour of sintered Cr and Mo steel

The microstructure, mechanical properties, and dry rolling-sliding wear resistance of sintered Fe-Cr-Mo alloy and steel (0.4%C) were investigated as a function of microstructure. Graphite enhances sintering of chromium alloyed powder owing to the effect of free carbon on the reduction of chromium oxide. A bainitic-martensitic microstructure is obtained after sintering with normal cooling on the carbon alloyed material. Impact properties are increased by the addition of graphite to the base powder. In the carbon alloyed material, they are higher in the as sintered condition than after heat treatment because of the lower ductility of tempered martensite than that of lower bainite. Wear behaviour is strongly influenced by hardness. The increase in hardness reduces delamination and favours the formation of a glazed surface during rolling-sliding, which significantly reduces the wear rate.