Microstructure and wear properties of novel sintered cold work steel and related particle reinforced composite materials

Abstract

In the field of wear resistant materials it is known, that for certain applications steel based composites produced by powder metallurgy are beneficial due to a higher wear resistance compared to conventional cast materials. Early developments of these high wear resistant MMC were dependent on hot isostatic pressing but latest experimental findings nowadays also allow for a production by liquid phase sintering. Several materials systems have already been investigated which, however, lack of a sufficient hardness in the as sintered state. Especially for wear resistant coatings it would be beneficial to avoid a separate hardening of a coated component. The low hardness in the as sintered state is related to the transformation kinetics of the metallic matrix of the coating materials, typically leading to a comparatively soft pearlitic microstructure, if the cooling rate is too low. The use of a nickel alloyed PM cold work steel as matrix material avoids this restriction, as the formation of pearlite and bainite is delayed significantly, improving the hardenability of the steel. Adding coarse hard particles of chromium carbide (Cr₃C₂), aluminium zirconium oxide (AlZrO) or titanium carbide (TiC) to the steel powder, composite materials with a high abrasive wear resistance can be obtained by liquid phase sintering. The development of these materials, supported by thermodynamic calculations, is presented here together with results of the microstructural investigation and wear tests.