718H模具钢等离子熔覆涂层的组织和性能研究

Study on Microstructure and Performance of Coating on 718H Mold Steel by Plasma Cladding

采用等离子熔覆技术在718H模具钢表面熔覆铁基合金粉末,借助光学显微镜、X射线衍射仪、扫描电镜、能谱仪、显微硬度计和材料表面性能综合测试仪对熔覆层的显微组织、化学成分、物相组成、显微硬度和摩擦磨损性能进行了分析。结果表明:等离子熔覆铁基合金粉末的熔覆层的组织近表面为细晶区,中间为柱状晶,熔覆层与热影响区的交界处有一条平面晶组织,熔覆层与基体形成了冶金结合,热影响区组织为板条状马氏体;从基体到表面硬度大致呈梯度分布,熔覆层的硬度达到800 HV,大于基体材料的硬度;熔覆层中有较多M7C3碳化物和γ-(Cr-Ni-Fe-C)合金固溶体相,磨损量小于基体材料的,熔覆层的耐磨性明显好于基体材料。

Fe-based alloy layer was coated on 718H mold steel surface by plasma cladding technology. The microstructure, phase constituent, chemical composition, hardness and wear resistance were characterized by OM, XRD, SEM, EDS, HV-1000 micro-hardness tester and material surface comprehensive performance tester. The results show that fine grains are observed near the surface of the coated layer, and columnar grain structures are observed under the surface. At the interface between cladding layer and heat affected zone, a planar grain structure is detected, and the coating is metallurgically bonded with the matrix. The heat affected zone is observed to be strip martensite structure. A gradient increasing distribution of hardness is detected from the matrix to the coating surface, where the surface of coating has the micro-hardness as high as 800 HV. MTC3 carbide and γ- （Cr-Ni-Fe-C） alloy solid solution are found in the coating. The wear mass loss of the coating is characterized to be lower than that of matrix＇s, indicating the wear resistance of coating material is better than that of matrix.