Cr-Mo激光合金化对灰铸铁组织及耐磨性的影响

THE EFFECT OF Cr-Mo LASER ALLOYING ON MICROSTRUCTURE AND WEAR RESISTANCE OF GRAY CAST IRON

系统地研究了灰铸铁Cr-Mo激光合金化层中合金元素的分布、显微组织和耐磨性。试验结果表明,当激光束功率和预涂层合金成分一定时,合金化层的合金浓度主要决定于激光扫描速度。适中的激光扫描速度(7mm/s)下,合金元素在层内分布较均匀,沿层深浓度梯度平缓,合金化层的组织为极细小均匀的树枝晶;其余扫描速度下,表面Cr-Mo浓度高,沿层深浓度梯度大,表面高合金浓度处组织为白亮层,次层为树枝晶和层片状莱氏体,随层深增加枝晶间距增大。Cr-Mo激光合金化显著提高了灰铸铁的硬度和耐磨性。

The alloying element distribution, microstructure and abrasion resistance of laser alloying layer on gray cast iron are systematically studied. The experimental results show that the alloy concentration distribution in laser alloying layer depends mainly upon the laser scanning speed for a defined coating composition under a constant power of a continueous laser beam. There is a very fine dendritic struc- ture in the layet with homogeneous alloy element distribution and gentle concentration gradient along the depth at the appropriate scanning speed of 7mm/s. But, at other scanning speeds, in surface layer a bright structure appears which is richer in Cr and Mo concentrations and steeper in concentration gradi- ent. In the subsurface layer a dentritic structure consisting of dentrite and interdendritically lamellar ledeburite exists and with the depth increasing the dendritic spacing increases. The hardness and abra- sion resistance of gray cast iron have been increased remarkably by means of the laser surface alloy- ing.