Fatigue characteristics of high speed steel P/M alloys
Hirano Akihiko; Nakayama Hideaki; Funakoshi Jun; Okano Hiroaki; Kosaka Akira
Abstract:In order to reveal the mechanical performance of powder metallurgical (P/M) alloys, several kinds of mechanical tests were carried out on three sorts of HIPed high speed steel P/M alloys. Three ingot metallurgical (I/M) alloys with almost the same chemical compositions as those of the P/M alloys were also used as reference materials. Dependence of mechanical properties on chemical composition and fabrication process was discussed in details. The P/M alloys show higher bending strength than I/M alloys irrespective of the difference in additive content. Fracture toughness of both P/M and the I/M alloys depends on Co content. Fatigue strength of the P/M alloys is higher than that of the I/M alloys. Fatigue crack growth rate of P/M alloys shows clear dependence on additive content; the greater the additive content, the higher the crack growth rate. Such a crack growth behavior of the P/M alloys can be correlated well with the size and the density of carbides distributed in the matrix of each P/M alloy. Key Words:powder metallurgical alloy, high speed steel, bending fracture strength, fracture toughness, fatigue crack growth rate,