激光器(Nd:YAG)工艺参数对熔覆层组织的影响

研究了采用Al、Si和Al2O3混合粉对AZ91D镁合金表面进行激光熔覆的工艺和熔覆层组织。激光加工是在一个5 kW固体激光器(Nd:YAG)上进行的,研究了Si和Al2O3颗粒在熔覆层中的体积分数、分布、形貌及其组织。较系统地研究了激光工艺参数对其组织和熔覆层显微硬度的影响。结果表明,熔覆层的平均显微硬度比基体AZ91D的(HV0.0560~70)高很多,可达HV0.05210;并且,随着激光功率的增加,熔覆层的显微硬度下降,这种情况在较低功率(小于2 kW)时更为明显。给出了用Al、Si和Al2O3混合粉激光熔覆AZ91D镁合金表面适当的工艺参数和均匀的复合层组织。

Effect of laser (Nd:YAG) parameters on microstructure of surface cladding layer

The laser surface cladding of AZ91D magnesium alloy with Al and Si and Al_2O_3 powders was investigated.Laser processing was carried out with a 5 kW Nd:YAG laser.The microstructure and phase analyses of the surface cladding layer were carried out;furthermore,the morphology of the cladding zone,volume fraction and distribution of the Si and Al_2O_3 particles in the laser surface cladding layer were also investigated.The average microhardness of the surface layer was measured in detail as a function of laser parameters.Microhardness of the surface layer was significantly improved to as high as 210 Hv_(0.05) as compared to Hv_(0.05) 60-70 of the AZ91D substrate,and the average microhardness of the cladding layer of the composite surfaced specimen decreases with increasing of laser power.However,the rate of decrease is faster at lower power.Though the average microhardness of the surface cladding layer remains constant,there is a little fluctuation in the reading in some regions possibly,because of the random distribution of hard particles in the cladding layer.Finally,the proper processing parameter ranges for formation of a homogeneous microstructure and enhancement of microhardness for laser surfacecladding of AZ91D with Al and Si and Al_2O_3were established.