抄録
Effects of the quenching temperature on the high temperature low cycle fatigue property of P/M hot work tool steel, which is a newly developed 4.2Cr-2.5Mo-V-Nb steel, were investigated in comparison with conventional ingot metallurgy products of the same grade. The fatigue life of P/M material quenched from 1403K was longer than that from standard quenching temperature, 1303K, while I/M material showed opposite tendency. The improvement of fatigue life of P/M material by quenching from high temperature was due to the finer grain and the increase of slip deformation stress because of the fine dispersion of carbides. The coarsening of grain, which was observed in I/M materials quenched from high temperature, promoted initiation and propagation of fatigue cracks and brought a decrease of the fatigue life. It was clarified that the grain size and high temperature hardness were important factors for high temperature low cycle fatigue property of hot work tool steels.
