Study on Residual Stress Distribution in Stellite-6 Cladding Layers on 420 Steel Steam Turbine Blades

To evaluate the residual stresses of Stellite-6 dissimilar layers on the water erosion-prone regions of lowpressure last-stage blades, the effects of the microstructure, microhardness and cladding passes on the residual stress distributions of cladding layers are investigated carefully. Although the cladded blades undergo stress relief heat treatment, the residual tensile stress in the cladding Stellite-6 layer is 200 similar to 300 MPa, and the residual compressive stress in the substrate is - 100 similar to - 150 MPa. Due to the microstructure and property mismatch between the cladding layer and substrate, there is a great residual stress gradient at the interface of the Stellite-6 alloy layer and substrate. The addition of cladding passes on the concave side of the blade can increase the peak tensile stress to 374 MPa in the other side cladding layer; however, the cladding pass significantly reduces the residual stress gradient at the interface of the Stellite-6 alloy layer and substrate. The reduced residual stress gradient of the interface indicates that adding a cladding layer is beneficial for improving blade service safety.