急冷凝固粉末法の高クロム鋳鉄への適用とその焼結合金の機械的性質および高温酸化特性

Abstract

Powder metallurgy process was adopted to improve the mechanical properties and the elevated temperatures oxidation resistance of high chromium cast irons with hypo- and hyper-eutectic compositions. Rapidly solidified powders produced by a centrifugal atomization process were used as a starting material. The powders were sintered by spark plasma sintering. Mechanical properties and high-temperature oxidation resistance of the sintered compacts were investigated and compared to those of the cast ingots. The sintered compacts have remarkably refined and homogeneous microstructure in comparison with the ingots. The hardness of the sintered compacts is higher than that of the ingots in both hypo- and hyper-eutectic alloys. The hardness of the hyper-eutectic sintered compact reaches 68 (HRC) on Rockwell C-scale. High-temperature oxidation resistance of the sintered compacts is superior to that of the ingots independent of the alloy composition. Weight gains of the hypo- and hyper-eutectic sintered compacts decrease a half and one-fifth compared with those of the ingots at 973 K, respectively. The excellent oxidation resistance of the sintered compacts can be ascribed to the formation of homogenous oxide film on the surface of the compacts due to the refined microstructure.