Mo对激光熔覆WC/Ni35涂层组织与性能的影响

Effect of Mo on microstructure and properties of laser cladding WC/Ni35 layers

针对高WC含量的WC/Ni35熔覆层容易出现裂纹的问题,在WC/Ni35熔覆层中添加2、5和8 mass%Mo元素,研究Mo对WC/Ni35熔覆层组织与性能的影响。结果表明:随着Mo元素含量的增加,WC/Ni35熔覆层组织更加致密细小,柱状晶减少,等轴晶增加。添加2和5 mass%Mo元素的熔覆层中,Ni _(17)W_(3)、Cr_(4)Ni_(15)W等新的硬质相数量增多,导致熔覆层平均硬度增大;添加8 mass%Mo元素的熔覆层中,物相较多以含Mo的韧性相存在,其平均硬度和添加5 mass%Mo元素的熔覆层持平。Mo元素含量增加到5 mass%时,熔覆层中产生新的W的化合物,减少W元素的偏析现象,同时Cr元素对钝化膜的修复作用,使熔覆层耐腐蚀性提高;添加8 mass%Mo元素的熔覆层由于Cr的析出导致出现贫Cr区,熔覆层的耐腐蚀性降低。添加8 mass%Mo元素的熔覆层没有产生裂纹。在高WC含量的WC/Ni35熔覆层中添加8 mass%Mo元素,可以获得无裂纹、组织致密的熔覆层,其硬度提高,耐腐蚀性略有降低。

In response to the issue that cracks are prone to occur in WC/Ni35 cladding layers with high WC content,2,5 and 8 mass%Mo elements were added to the WC/Ni35 cladding layers,and the effect of Mo on microstructure and properties of the WC/Ni35 cladding layers was studied.The results show that with the increase of Mo element content,the microstructure of the WC/Ni35 cladding layers becomes denser and finer,with a decrease in columnar crystals and an increase in equiaxed crystals.In the cladding layers with 2 and 5 mass%Mo elements added,the number of new hard phases such as Ni _(17)W_(3)、 and Cr_(4)Ni_(15)W increases,leading to an increase in the average hardness of the cladding layers.In the cladding layer with the addition of 8 mass%Mo element,more phases exist as ductile phases containing Mo,and its average hardness is the same as that of the cladding layer with the addition of 5 mass%Mo element.When the Mo element content increases to 5 mass%,new W compounds are generated in the cladding layer,reducing the segregation phenomenon of W element.At the same time,the repair effect of Cr element on the passivation film improves the corrosion resistance of the cladding layer.The addition of 8 mass%Mo element in the cladding layer results in a Cr poor zone due to the precipitation of Cr,thereby causing a decrease in the corrosion resistance of the cladding layer.There are no cracks in the cladding layer with 8 mass%Mo element added.Adding 8 mass%Mo element to the WC/Ni35 cladding layer with high WC content can obtain a crack-free and dense microstructure,with an increased hardness and a slightly reduced corrosion resistance.