摘要
透射电镜研究表明38CrMoAlA钢经渗氮处理后表层组织是以γ′和ε为基体。γ′颗料细小,类似多晶无择优取向分布,ε外形类似针状或条状,首次发现二种铁氮化合物相内均有超细弥散的合金氮化物CrN、Cr_2N、AlN析出,提出了白亮层高硬度高脆性的本质。
The TEM study shows that the microscpic structure of superficial layer of 38CrMoAlA steel is composed of γ'-Fe_4N and ε-Fe_3N after first queuching at 930℃ in oil and tempering for 1.5h at 680～700℃ and then nitriding for 60h at 500～520℃ in ammonia and denitriding for 2h at 560℃. The morphology of γ'-Fe_4N is irregular fine granular being distributed as polycrystal and that of ε-Fe_3N is needle-like or lath-like. It has been discovered for the first time that superfine dispersed alloy element nitrides CrN, Cr_2N, AlN precipitated from both ε-Fe_3N and γ'-Fe_4N. The mechanism of highhardness and brittleness for white bright layer after nitriding is suggested
