激光功率对高速激光熔覆Ni/316L层组织与力学性能的影响

Effect of laser power on microstructure and mechanical properties of high-speed laser clad Ni/316L layer

为研究高速激光熔覆Ni/316L层组织与力学性能随激光功率的演变规律,分别采用1.1、1.3和1.5 kW激光功率在Q235钢表面熔覆Ni/316L层。采用扫描电镜(SEM)、能谱仪(EDS)、显微硬度计、冲击试验机及Knoop压痕法研究了熔覆层的显微组织、显微硬度、冲击性能与弹性模量。结果表明,激光功率为1.1 kW时熔覆层内部晶粒生长取向存在垂直于界面生长和与界面成一定角度交叉生长两种模式,并含有少量孔隙等缺陷,熔覆层/基体界面元素成断崖式分布,二者互扩散程度较低。随着激光功率升高,熔覆层晶粒转变为以垂直于界面生长为主,且涂层内部致密性高,缺陷较少,熔覆层/基体界面元素互扩散程度提升。激光功率对熔覆层硬度、冲击性能都存在显著影响,但是对弹性模量的影响较低。不同激光功率下,熔覆层最大硬度均出现在距界面100μm左右的区域;功率从1.1 kW提升至1.5 kW时熔覆层熔合区最大硬度提高约50%;功率为1.5 kW时,试样的冲击性能较基体提高约20%。

In order to evaluate the effect of laser power on microstructure and mechanical properties of the Ni/316 L layer deposited via highspeed laser cladding,the Ni/316 L layer was clad on the Q235 steel surface under laser power of 1.1,1.3,and 1.5 k W respectively.The microstructure,Vickers hardness,impact property and elastic modulus of the laser clad layers were examined by means of scanning electron microscope(SEM),energy dispersive spectrometer(EDS),Vickers hardness tester,impact testing machine and Knoop indentation method.The results show that when the laser power is 1.1 k W,the grain growth in the laser clad layer contains perpendicular-to-interface growth mode and slant growth mode,the clad layer also has a small amount of pores and other defects,and the elements at the clad layer/substrate interface are distributed in a cliff-like manner,which means that the element diffusion between the substrate and the clad layer is limited.As the laser power increases,the perpendicular-to-interface growth mode of grains becomes the main mode,and the porosity of the clad layer is lower and the defect is less,the interdiffusion degree of elements at the clad layer/substrate interface is improved.The laser power has a significant effect on hardness and impact property of the clad layer,but has little effect on elastic modulus.The maximum hardness of the clad layer with different laser power is always about 100μm away from the interface.When the laser power increases from1.1 k W to 1.5 k W,the maximum hardness of the clad layer fusion zone is increased by about 50%,and the impact property of the clad layer specimen is about 20%higher than that of the substrate when the laser power is 1.5 k W.