电火花加工对奥氏体不锈钢气体渗氮的影响

Effect of electrical discharge machining on gas nitriding of austenitic stainless steel

将电火花线切割316奥氏体不锈钢试样在450℃下进行气体渗氮8 h。分析原始面和线切割面渗氮后的显微组织、渗层相结构及元素分布,并对其硬度、耐磨性和耐蚀性进行测试。结果表明,线切割面渗氮后得到了更厚的渗层,渗层由S相(扩展奥氏体相)组成,渗氮后硬度和耐磨性大幅提高,而耐蚀性基本不变。线切割促进渗氮的原因在于电火花加工过程中快速冷却形成表层马氏体,促进活性氮原子的快速扩散。

A 316 stainless steel sample was prepared by wire-cut electrical discharge machining（EDM） , and followed by gas nitriding at 450 ℃ for 8 h. The thickness, mierostrueture and properties of nitrided layer were investigated. The results show that the EDM surface produces much thicker nitriding layer, the nitrided layer is composed of S phase, and exhibits higher surface hardness and good resistance to wear and corrosion. The martensite layer formed in EDM process is believed to accelerate the diffusion of nitrogen.