Cr-Mo-Fe系合金の時効硬化について

Abstract

By means of hardness measurement and microscopic observation, the aging characteristics of Cr-Mo-Fe alloys were investigated, on ternary alloys containing 5∼65%Cr and 5∼30%Mo, as well as a CM-469 alloy (60%Cr, 25%Mo, bal.Fe), prepared by rapid melting in a carbon-resistance furnace and in an inert arc furnace, respectively. The alloys were solution treated at 1250°C, and then aged at 600°∼900°C for period up to 1000 hrs. The results obtained are summerized as follows: (1) Age-hardening takes place in the α-phase region of the ternary system due to the precipitation of ε-, χ-, and σ-phases, respectively, according to Cr content. (2) In alloys with less than about 50%Cr, their hardness in solution treated as well as age hardend states, and their optimum aging temperature are raised with increase of Cr and Mo contents. (3) In alloys with more than about 50%Cr, the precipitation of σ-phase takes place very slowly, its precipitation hardening being raised with increase of Mo content but contrarily with decrease of Cr content; this suggests the superiority of Cr-base alloys in creep-resisting properties at high temperatures. (4) Differences in aging characteristics due to melting method were also discussed for a CM-469 alloy, arc-melted versus air-melted.