Abstract: The nanoindentation method, which is a non-destructive testing technique, is used to measure the residual stress of plasma sprayed Fe-based coating. Tensile stress is proved to be generated on the coating surface through comparing the load-depth curves of stress-free and stressed coatings. As significant pile-up deformation is observed around the indents of both stress-free and stressed coatings, the commonly used Oliver method is not available to calculate the true contact area, which is the characteristic parameter of residual stress. The early established formula for the calculation of true contact area of pile-up material is used to obtain the true contact areas of stress-free and stressed coatings. Based on the difference of the contact areas, the residual stress with the value of 188 MPa is obtained, which agreed well with that (162 MPa) by XRD method.

Key words: Fe-based coating, Nanoindentation, Pile-up, Residual stress