利用半导体激光器在汽轮机末级叶片材料17-4PH不锈钢表面激光熔覆Stellite6合金涂层，然后分别制备17-4PH不锈钢、17-4PH不锈钢表面激光熔覆和17-4PH不锈钢表面激光熔覆后经550 ℃×6 h热处理的疲劳试样，进行高周拉压疲劳试验,并对疲劳断口进行扫描电镜（SEM）分析。试验结果表明：在107循环周次条件下，基材17-4PH不锈钢的疲劳极限为470 MPa，基材表面激光熔覆Stellite6合金涂层试样的疲劳极限下降到380 MPa,而基材表面激光熔覆Stellite6合金涂层经过热处理后的试样可达到440 MPa；基材17-4PH不锈钢的裂纹源通常位于表面、近表面或内部缺陷处，裂纹扩展区具有明显的疲劳辉纹特征，瞬断区为韧窝特征；而熔覆试样的裂纹源位于熔覆层侧的缺陷处或熔覆层与基体的界面结合处，然后向熔覆层和基体两侧扩展，熔覆层侧呈脆性沿晶断裂，基体呈韧性疲劳断裂。

Stellite6 coating is cladded on the 17-4PH stainless steel using a diode laser. Fatigue behaviors of substrate specimens, as-cladded specimens and the cladded specimens with heat treatment (550 ℃ for 6 h) are tested with the tension and compression loading method. The fracture surface is characterized by scanning electron microscopy (SEM). The results show that the fatigue strength with 107 cycles of substrate specimens is 470 MPa which is higher than that of the as-cladded specimens with 380 MPa, while the fatigue strength of cladded specimens with heat treatment can reach to 440 MPa. The fatigue surface of substrate specimen shows that the fatigue crack initiates at the surface or inner defects, then propagates forward with the parallel fatigue striations and dimple appearance, while the crack of cladded specimens initiates at the defects in the coating or the interface between the coating and the substrate, then extends to the coating which shows the brittle inter-dendritic fracture and the substrate shows the ductile fatigue fracture respectively.