铁基合金＋WC激光熔覆层的显微组织与性能

Microstructure and properties of Fe-base alloy +WC laser cladding layer

在Q235钢和QT-600球铁表面激光熔覆铁基合金+WC粉末。利用扫描电镜(SEM)、光学显微镜(OM)、能谱仪(EDS)和X射线衍射仪(XRD)分析了熔覆层的微观组织,测试了熔覆层硬度和磨损性能。结果表明,Q235钢表面熔覆层组织较细,熔覆层与基体结合界面波形不明显,且出现白亮层。QT-600球铁表面熔覆层组织粗大,界面波形较大,基体混入多,无白亮层,硬度、耐磨性相对较低。分析认为,组织与性能的不同是由于Q235钢熔点较高,熔化量少,且熔池冷速快,组织细化。QT-600球铁表面熔覆层组织不均匀,其中等轴晶的耐磨性高于柱状晶,原因在于较细的等轴晶晶界较多,增大了滑动阻力。

Laser cladding of Fe-base Alloy ＋ WC powders on Q235 steel and QT-600 spheroidal graphite cast iron substrates was carried out. The microstructure, microhardness and wear resistance of the laser cladding layers were analyzed and tested with scanning electron microscopy（ SEM ）, optical microscopy （OM）, energy-dispersive spectrometer（EDS） and X-ray diffraction （XRD）. The results show that the microstructure of the laser cladding layer on Q235 steel surface is fine, the interface between the coating and substrate is unconspicuous wavy and appears a bright layer. While the microstructure of the laser cladding layer on QT-600 spheroidal graphite cast iron surface is coarse. The wavy interface becomes more obvious and the interlarded amount of substrate is more. No bright layer appears. The hardness and wear resistance of the composite coating are relative lower. It is considered that the difference of the microstructure and properties is due to the higher melting point of Q235 steel which decreases the melted amount and the rapid cooling rate of laser molten pool which results in refined microstructure. The microstructure of the laser clading layer on QT-600 spheroidal graphite cast iron surface is un-uniform;equiaxed grains have higher wear resistance than that of columnar grains because equiaxed grains have more crystal boundary and enhance the resistance to slip.