电子束扫描对熔化区显微组织及性能的影响

为提高H13模具钢的使用寿命，采用热喷涂技术在H13钢表面制备Ni60A合金层，利用电子束扫描的方法处理表面合金层。研究电子束扫描处理对H13钢表面合金层及基体熔化区组织和性能的影响。采用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、显微硬度计和磨损试验机对H13钢电子束表面合金层及基体熔化区的显微组织、成分、硬度和耐磨性进行分析测试。结果表明：经电子束扫描后，Ni60A合金层与H13钢基体完全熔合在一起，形成冶金结合，扫描处的组织形态可以分为4个区域：即熔化区、过渡区、热影响区和基体。合金层组织由层片状组织转变为短小的枝晶和柱状晶，H13钢基体熔化区的组织可分为： 熔池上部的等轴晶区、熔池中部的柱状晶区和熔池底部的枝晶区。合金层的显微硬度值为340~380 HV0.1，比未处理前Ni60A合金层的硬度有所提高，磨损形式主要为磨粒磨损和断续的较浅的犁沟磨损，在整个磨损试验过程中磨损失重很小，耐磨性得到提高。

Effects of Electron Beam Scanning on Microstructure and Properties of Melting Zone

To improve the H13 steel working life, the method of thermal spraying is adopted to prepare Ni60A alloy layer on the surface of H13 steel and the method of electron beam scanning is used to process the surface alloy layer. The effect of electron beam scanning on structure and properties of substrate melting zone and surface alloy layer of H13 steel is researched. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Xray diffraction (XRD), microhardness tester and abrasion machine are used to analyze the microstructure, component, hardness, and abrasion resistance of the substrate melting zone and surface alloy layer of H13 steel scanned by electron beam. The experiment results show that after the scanning of electron beam, Ni60A alloy layer and H13 steel substrate are completely fused together and metallurgical bonding is formed; the microstructure form of the scanned zone can be divided into four zones: melting zone, transition zone, heataffected zone and substrate. The structure of the alloy layer transforms from lamellar structure to smallish dendrite and columnar crystals. The melting zone structure of H13 substrate can be divided into three parts: equiax crystal zone at the upper part of the melting zone, columnar crystal zone in the middle part of the melting zone and dendrite zone at the bottom of the melting zone. Microhardness of the alloy layer is from 340 to 380 HV0.1 and is larger than that of Ni60A alloy layer unprocessed. The abrasion forms are mainly abrasive wear and spiccato shallow plough wear. The wear volume is very small in the whole wear experiment and the abrasion resistance is improved.