TiO2对铁基合金激光熔覆层组织和性能的影响

在 4 5 #钢基底上进行了铁基合金和铁基合金加TiO2 的激光熔覆对比实验。采用渗透法观察熔覆层表面裂纹 ,利用金相显微镜和扫描电镜观察熔覆层横断面的显微组织 ,使用X射线衍射仪对熔覆层进行物相分析 ,并测试了熔覆层横断面的硬度分布和熔覆层的摩擦磨损性能。结果表明 ,在一定的工艺条件下 ,添加适量的TiO2 ,可以获得成形良好、无裂纹、组织致密均匀、耐磨性好的高质量铁基激光熔覆层。适量的TiO2 可使涂层共晶体数目增多且分布均匀 ,组织细化 ,裂纹消失 ,在降低涂层裂纹敏感性的同时仍保持涂层的硬度和耐磨性不降低。TiO2 对铁基熔覆层性能改善的原因是 :适量TiO2 的加入 ,在涂层中可形成Cr13Fe35Ni13Ti7金属间化合物 ,熔覆层组织由亚共晶组织转变为性能较好的伪共晶组织 ,且由于高熔点的Ti硼化物的析出 ,提高了形核率 ,使组织颗粒细化、均匀。

Effect of TiO2 on the microstructure and properties of Laser cladding layers of Fe-based Alloy

The laser cladding of Fe-based alloy doped without and with various concentration of TiO2 on steel 45 by powder feeding were carried out. A good finish, crack-free, fine structure and perfect performance coating was produced with a proper content of TiO2 and suitable laser processing parameters. The structural observation on the cross-section of laser coatings by an optical microscope and a scanning electron microscope (SEM) was performed, and the phase analysis by X-ray diffraction (XRD) was accomplished. The cracking observation on surface of the coatings, the hardness measurement in the cross-section of the clad layers and tribotesting tests were also completed. It is shown that adding suitable amounts of TiO2 to Fe-based alloy is benefit to increase the concentration of fine eutectic and reduce the cracking susceptibility, which is attributed to the formation of a pseudo eutectic that contains a intermeallic compound of Cr13Fe35Ni13Ti7, a γ(FeNi) solid solution and fine titanium boride particles tha