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1、前言钢和铁渗氮所形成的渗层,一般区分为接近表面的化合物层和在化合物层下的扩散层(见图1[1])。传统的气体渗氮工艺,于765～815K 在氨气中渗氮20～80h,一般适用于提高零件的抗疲劳性,疲劳性能的改进归因于渗氮时扩散层形成残余宏观和微观应力[2、3]。最近,已经发展了几种渗氮工艺,特别是扩大了形成具有良好耐磨性和抗腐蚀性的化合物层,而仍能有效地改进其疲劳寿命[4]。在不仅向试件提供氮而且也提供碳的情况下,这种热处理工艺称作(铁素体)氮碳共渗(835～855K,2～8h)。对于化合物层的显微组织和相应的耐磨性及抗腐蚀性还远未认识清楚。因此,考虑到近
1. INTRODUCTION The diffusion layer formed by nitriding of steel and iron is generally divided into a compound layer near the surface and a diffusion layer below the compound layer (see Figure 1 [1]). The traditional gas nitriding process nitriding nitrogen in ammonia gas for 20-80h at 765-815K is generally suitable for improving the fatigue resistance of parts and the improvement of fatigue performance is attributed to the formation of residual macro and micro stress in the diffusion layer during nitriding [ 2,3]. Recently, several nitriding processes have been developed, in particular, the formation of a compound layer having good abrasion resistance and corrosion resistance has been broadened while still effectively improving the fatigue life [4]. This heat treatment process is referred to as (ferritic) nitrocarburising (835-855K, 2-8h) in the case of not only supplying nitrogen to the test piece but also providing carbon. For the compound layer microstructure and the corresponding wear resistance and corrosion resistance is far from clear. Therefore, taking into account the recent