X-Ray Stress Measurement of Composite Plating (Ni-Co-P/α-Si₃N₄)

Residual Stress Measurement of Ni-Co-P Phase under the Consideration of the Stress Gradient

Abstract

Ni-Co-P/α-Si₃N₄ composite plating excels in wear-and corrosion resistance. It is important to evaluate the residual stress due to the misfit of mechanical and physical properties between plating and substrate during the manufacturing and industrial using. However, in the case of plating specimen which have stress gradient, the sin²Ψ method is not adequate to use because this material shows severely curved sin²Ψ diagram.
In this study, a fundamental investigation was carried out to apply the X-ray residual stress measurement of the plating material. Fourth kinds of specimens with different thickness of film were prepared. X-ray elastic constants were obtained using the non-liner analysis. Influence of the film thickness on curvature of 2θ-sin²Ψ diagram was simulated. Residual stress in the plating layer was analyzed under the assumption that the stress state is equivalent biaxial.
Some experimental results were observed: sin²Ψ diagrams were severely curved, and shape of diagrams shows varied by the film thickness and X-ray penetration depth. There is the steep stress gradient in the direction of depth.As the results, X-ray elastic constants of all specimens were independent from the thickness of film. Therefore, the value is constantly. A value of residual compressive stress calculated form present method is grater than value of sin²Ψ technique. Compressive stress decreased with the film thickness.