激光熔覆添加碳化钨的镍基合金应力状况研究

在20Cr2NiSiW基体上熔覆添加碳化钨的镍基合金．对熔覆层的应力状态进行了分析。未预热的熔覆层存在热应力的残余应力峰值700MPa．和相变应力的残余应力峰值850MPa。熔覆件整体的熔前预热和熔后保温。可以改善熔覆层的应力分布。消除部分热应力和相变应力，残余应力也有所降低。虽然仍呈现熔覆层受拉应力，热影响区受压应力的状态．但热应力的峰值降到510MPa．热应力峰也从表面移到了熔覆层的中部。界面的相变拉应力峰被消除．得到了应力分布状态较好的激光熔覆层。在未预热的熔覆层内，先共晶的奥氏体枝晶的生长，从界面开始逆温度梯度方向定向生长．直到熔覆层的表面。而在预热的熔覆层内．先共晶的奥氏体的生长方向变为从熔池的四周垂直于熔池的边界生长．到熔覆层的中部结束。

Study on Stress Status of WC Doped Ni-Based Alloy by Laser Cladding

For the laser cladding of WC doped Ni based alloy on 20Cr2NiSiW substrate, the stress status of cladding layer are analyzed .The thermal residual stress of laser cladding layer without preheating is 700 MPa, and phase changing residual stress is 850 MPa. The stress distribution of cladding layer can be ameliorate with preheating before cladding and thermal retardation after cladding. The part of thermal stress is relieved and the residual stress of phase changing is descend. Although the cladding layer still is compressive stress and the heating affected zone is stretching stress, the thermal stress peak is decrease to 510 MPa and shifted from face to intermediate section of cladding layer. The interface peak of stretching stress of phase changing is relieved, and satisfaction of stress status of cladding layer is obtained. On the non preheating cladding layer, the eutectic austenite dendrite growth is along the opposite direction of temperature gradient beginning from interface to face of cladding layer. On the preheating cladding layer, the eutectic austenite dendrite growth is changed from beginning the perpendicular border of cladding pool to intermediate section of layer.