激光熔覆基板的弯曲变形与残余应力研究

Analysis of Bending Deflection and Residual Stress for Substrate of Laser Cladding

薄板类零件激光熔覆时基板变形显著,目前有关熔覆层和基板残余应力分布与基板弯曲变形的相关性未见研究报道。使用Nb:YAG固体激光器,通过改变激光功率和扫描速度,在304不锈钢基板上熔覆Ni60A自熔性合金粉末,测量了样品的翘曲角度,并使用XRD测定了不同参数下样品熔覆层以及基板底部的残余应力。研究发现,样品基板发生正向弯曲变形,并且垂直于扫描方向。熔覆层平行于扫描方向为拉应力,垂直于扫描方向为压应力;基板底部平行于扫描方向为压应力,垂直于扫描方向为拉应力。随着激光功率的增加,基板的翘曲角度与熔覆层残余应力和基板底部残余应力均增加,P=1 300 W时翘曲角度最大,残余应力最大;随着扫描速度的增加,基板的翘曲角度先减小再增加,熔覆层残余应力和基板底部残余应力先降低后增加,v=70 mm/min时翘曲角度最小,残余应力最小。

The Nb:YAG solid state laser was used to clad Ni60 A self-melting alloy powder on 304 stainless steel substrate by alternating the laser power and scanning speed.The bending angle of the sample was measured,and the residual stress of the cladding layer and the substrate bottom for different parameters was detected by XRD.Results showed that the sample substrate was bent along the laser beam direction,perpendicular to the scanning direction.The stress parallel to the scanning direction was tensile,and the stress perpendicular to the scanning direction was compressive on the cladding layer surface.On the contrary,the stress parallel to the scanning direction was compressive and the stress perpendicular to the scanning direction was tensile at the bottom surface of the substrate.With the increase of laser power,the bending angle and the residual stress of cladding layer and the bottom of the substrate increased gradually.When P=1 300 W,the bending angle and residual stress reached the maximum.Meanwhile,with the increase of scanning speed,the bending angle and the residual stress firstly decreased and then increased.When v=70 mm/min,the residual stress declined to minimum.