采用正交试验法设计气体渗氮试验, 综合分析了渗氮前回火温度、渗氮温度、渗氮时间、氨分解率四个工艺参数对H13钢渗氮层深度及显微硬度的影响, 得到了优化的渗氮工艺, 并与优化前的工艺进行对比。结果表明: 渗氮温度对渗层硬度的影响最为显著, 随渗氮温度的升高, 表面硬度先增加后降低; 氨分解率对渗层深度影响最为显著, 随着氨分解率的增大, 渗层深度先减小后增大; 最佳渗氮工艺为渗氮前560 ℃回火、渗氮温度535 ℃、渗氮时间15 h、氨气分解率50%; 与原始工艺相比, 优化后的渗氮工艺制备的渗氮层具有更大的渗层深度和硬度。

The effects of the various process parameters (tempering temperature before nitriding, nitriding temperature, nitriding time and resolution ratio of NH3) on the depth and micro-hardness of H13 steel nitride layer were analyzed and compared comprehensively through the orthogonal experimental design. The optimized nitriding process was given, and was compared with the original process before optimization. Results show that nitriding temperature was the most obvious factor for the hardness of nitride layer, and with the increase of nitriding temperature, the surface hardness increased first, then decreased. Resolution ratio of NH3 was the most obvious factor for the depth of nitride layer, and with the increase of resolution ratio of NH3, the depth of nitrided layer decreased, then increased. The optimized nitriding process was obtained as following: the tempering temperature before nitriding was 560 ℃, the nitriding temperature was 535 ℃, the nitriding time was 15 h, and the resolution ratio of NH3 was 50%. Compared with original nitriding process, the nitride layer of H13 steel prepared by optimization process had a higher hardness and a larger depth.