H13钢RE-N-C-S-V-Nb多元共渗成分优化

Formula Optimization on RE-N-C-S-V-Nb Multi-elements Penetrating for H13 Steel

用RE-N-C-S-V-Nb盐浴多元共渗的方法对H13钢表面进行改性处理,形成了含有钒铌碳氮化物的高性能复合层。以多元共渗渗层厚度和显微硬度作为正交试验的参考指标,对多元共渗配方成分进行优化。根据正交试验中各因素水平对指标的影响结果得到最优的成分为:硼砂盐浴中,稀土质量分数5%,V2O5质量分数6%,Nb2O5质量分数6%;盐浴回火中,稀土质量分数1%,CNO-质量分数34%。利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对多元共渗层的组成和显微结构进行了分析和研究,结果表明:共渗后试样表面形成了NbN、VN、NbC、V8C7等高性能物相和组织,渗层厚度达100～120μm且组织致密并呈弥散性分布。与常规氮化处理的试样比较,高温氧化增重速率缓慢仅为氮化处理的1/4,微裂纹出现在热疲劳循环2 000次以上。

A new RE-N-C-S-V-Nb multi-elements salt penetrating method was carried out to improve the surface properties of H13 steel. High-performance vanadium and niobium carbonitride composite coatings were formed on the surface. Thickness and microhardness of RE-N-C-S-V-Nb multi-elements penetrating infiltration layer for H13 steel samples were analyzed by orthogonal experiment method. According to the effect of various levels of factors on the indi- ces, optimum composition in borax salt-bath is obtained, that is 5%RE, 6% V2O5 and 6% Nb2O5, in salt-bath tempering, with 1% RE and 34% CNO-. The microstructure and composition of the composite coatings were analyzed by means of scanning electron microscopy and X-ray diffraction. The results show that high-performance NbN,VN,NbC,VsC4 phases and organizations are prepared in the infiltration layer. The thickness of permeation layer is up to 100～120μm and the microstructure shows compact and diffuse distribution. Its high-temperature oxidation rate of weight gain is 0.25 times slower than that of the conventional nitrided sample, and micro-cracks appear in more than 2 000 times thermal fatigue cycles.