激光重熔对Ni/WC涂层组织结构的改善机制研究

为了进一步探讨激光重熔等离子喷涂金属陶瓷涂层的组织与性能。本文通过等离子喷涂设备在45钢表面上制备了Ni/WC金属陶瓷涂层,再进行激光重熔处理,然后利用SEM、XRD、Photoshop软件及显微硬度测试仪等分析测试手段研究了该涂层在激光重熔前后的组织性能变化。结果表明:激光重熔前涂层为典型的层状结构,基体与涂层的结合面为机械结合,涂层内有大量未熔WC颗粒,且XRD检测其高温作用使得喷涂颗粒发生分解,分解出的C元素与其他元素发生反应生成新的化合物,丰富了涂层的硬质相;激光重熔后涂层中颗粒细化,分布均匀且能消除涂层中大部分孔隙和WC团聚。WC再次发生分解,生成新的硬质相,与周围的Ni形成“软基相+硬质点”的组合分布,基体与涂层的结合方式由机械结合转变为冶金结合。孔隙率由7.02%降到了3.08%,显微硬度也相应提高,且涂层显微硬度比基体高了255HV。

Study on improvement mechanism of laser remelting on the Ni/WC coating microstructure

In order to further investigate the microstructure and properties of plasma sprayed ceramic coating by laser remelting,Ni/WC cermet coating was prepared on the surface of 45 steel by plasma spraying equipment,and then laser remelting was carried out.After that,the microstructure and properties of the coating were studied by SEM,XRD,Photoshop software and microhardness tester before and after laser remelting.The results show that plasma spray coating is a typical layered structure,and the bonding surface between the matrix and the coating is mechanically bonded.There are plenty of untreated WC particles in the coating,but the spray particles are decomposed at high temperature,meanwhile,the decomposed C element reacts with other elements to generate new compounds,which enriches the hard phase of the coating.However,the particles in the coating after laser remelting is uniform and can eliminate most of the pores and WC agglomeration in the coating.WC is decomposed again,resulting in a new hard phase,and form a "soft base phase + hard point" of the combined distribution with the surrounding Ni.In addition,the combination of coating translates the mechanical combination into metallurgical bonding.The porosity decreases from 7.02% to 3.08%,and the microhardness increases accordingly,and the microhardness of the coating was higher than that of the substrate by 255 HV.