Microstructure and properties of Zr/FeCSiB layers produced by laser cladding
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摘要: 采用激光预置熔覆法,通过在FeCSiB合金粉末中添加一定比率的强碳化物形成元素Zr,在中碳钢基体上制备原位析出的颗粒增强铁基复合材料表层。利用光学显微镜、场发射电子扫描显微镜(能谱仪)和金相组织分析系统,对熔覆层显微组织、硬质颗粒的成分及其分布规律进行了观察与分析。其显微组织特征是树枝状的先共晶奥氏体分布在共晶基体上的亚共晶介稳组织;奥氏体在随后的冷却过程中转变为马氏体;熔覆层与基体成良好的冶金结合。熔覆层内析出的硬质颗粒是以ZrC为主的复合碳化物,主要分布在枝晶内与枝晶间;单道搭接熔覆层颗粒的体积分数分别为1.96%、2.2%～3.84%;显微硬度值在800HV0.2～1100HV0.2之间。Abstract: Fe-based composite layers reinforced by in situ ZrC particles were formed by laser overlapping and single cladding using preplaced FeCSiB alloy powders on a medium carbon steel matrix. The morphologies,microstructures,interface structure and the distribution of the ZrC particles in the clad layers were observed with optical microscopy,field emission electric scanning microscopy (FEEM). The microstructure of ZrC-reinforced Fe-based composite layers is the typical γ austenite dendrite and cellular distributed on the eutectic substrate. The energy dispersive spectroscopy (EDS) analysis shows the reinforcements are in situ synthesis carbides which main compositions consist of transition elements Zr,Mo and carbon. The compound carbide particles distributed within dendrite and interdendritic regions with 1.96%,2.2%～3.84% volume fractions for single and overlapping layers respectively. The martensite transformation went with the rapid cooling processes also. The Fe-based composite layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The microhardness values across layer cross section vary between 800HV0.2～1100HV0.2.
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Keywords:
- laser cladding /
- metallurgical bonding /
- hypoeutectic /
- compound carbide
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