铸钢表面镍基合金渗层的组织分析

Analysis on Microstructure of Ni-based Infiltrated Layer on Cast Steel Substrate

采用负压铸渗技术在ZGCr5Mo表面制备了镍基合金渗层,渗层厚度0.7～1.6mm。用扫描电镜、X射线衍射(XRD)、电子探针(EPMA)和硬度计等手段,分析了渗层的微观组织结构、渗层内元素分布、宏观/显微硬度等。结果表明:所得表面合金渗层组织致密,渗层与基体呈冶金熔合;渗层主要由Ni基固溶体、Ni3B、Cr3B、CrB等过饱和条件下形成的金属间化合物等相组成;渗层的镍基固溶体具备良好的韧性,金属间化合物等硬质起到强化作用,使渗层的硬度提高,宏观硬度可达56 HRC,显微硬度自渗层到基体呈梯度变化。

Ni-based surface alloying infiltrated layer was fabricated on cast steel ZGCr5Mo substrate by vacuum infiltration casting process.The thickness of infiltrated layer is about 0.7-1.6 mm.The microstructure of infiltrated layer,the distribution of chemical constituents among the infiltrated layer,then the microhardness for infiltrated layer was investigated by SEM,XRD,EPMA and hardness tester.The results show that： the microstructure of infiltrated layer is compactness and no any inclusion,micro-poles and micro-cracks happen among the infiltrated layer.The interface between the surface infiltrated layer and substrate belonging to metallurgical fusion was studied.The surface infiltrated layer is mainly composed of Ni-based solid solution,Ni3B,Cr3B and CrB intermetallic compound,which can enhance the hardness,strength and wear performance of the infiltrated layer.The microhardness of the infiltrated layer reaches 56 HRC.The distribution of microhardness from the surface of infiltrated layer to substrate presents gradient change.