410不銹鋼表面滲碳硬化與鈍化

Abstract

用於塑膠工業的模具及刀具，常需要同時具備良好的耐磨性及耐蝕性。一般的工具鋼雖然有良好的耐磨性，但耐蝕性卻相當;而沃斯田鐵系的不銹鋼，其特性則是恰巧相反，即耐蝕性極佳，耐磨性不足。因此如何利用表面處理的方式，來使材料同時具有良好的耐磨性及耐蝕性，實為提升塑膠模具工業水準的一重要研究。本研究針對SUS410 不銹鋼作真空滲碳熱處理，探討在不同的實驗參數製程下其顯微結構與硬度的變化，進而尋找最佳製程參數。實驗利用化學研磨、電解拋光、機械研磨、化學鈍化...等不同的表面處理方式，來重建不銹鋼表面的耐蝕性，最後再利用極化曲線作耐蝕性測試，並分析表面各元素與化合物之分佈情形。結果顯示，SUS410 不銹鋼再經真空滲碳處理後可得到表面硬度HV650 ，心部HV460 且內外皆為均勻的麻田散鐵組織。若後續再施以電解拋光、機械拋光或化學研磨等表面處理後，耐蝕性的提升並不明顯;但若再施以化學鈍化處理，將可有效提升其耐蝕性，唯化學研磨後再經鈍化處理者，因表面呈現多孔狀而耐蝕性下降。

As a molding and cutting material for plastic forming industry, tool steel is always used for its excellent wear resistance. But its poor corrosion resistance limits the productuvity of plastics. On the contrary, stainless steel owns excellent corrosion resistance but poor wear resistance. To improve the surface hardness of 410 martenstic stainless steel, a heat treatnent of vacum carburization process was carried out, and then was followed by electrolish, chemical polish, mechanical polish, and chemical passivation processes to recuperate the corrosion resistance of the steel. In this experiment, the process parameters, such as gas composition, gas flow rate, diffusion time etc., all had been optimized. The surface condition and cerbon and chromium distribution in the surface layer were examined and analyzed by EPMA, XRD, SEM-EDX and GDS. It was expected to develop a surface modified 410 stainless steel with better wear and corrosion resistance. Experiment results show that after the optimized vacuum carburizing process, SUS 410 stainless steel may reach a hardness of HV650 in surface layer and HV460 inside the matrix with fully martensite structure. After some surface treatment, such as electropolishing, chemical polishing, and mecharical polishing, the corrosion resistance of the alloy surface can not be improve significantly, but can be improve by the final chemical passivation process. Only the alloy sample treated by the vacuum carburization followed by chemical polishing and chemicalpassuvation shows a worse corrosion resistance, because of its porous surface structure which can not form a continuous chromium oxide layer.