Effect of work-hardening capacity on the gradient layer properties of metallic materials processed by surface spinning strengthening

The gradient layer induced by surface mechanical strengthening attracts plenty of attention as it can effectively improve the service performance of metallic materials, but how to design a suitable gradient layer and evaluate gradient layer properties need to be investigated further. In this work, the 316 stainless steel and TC4 alloy processed by surface spinning strengthening (3S) were investigated, including the work-hardening capacity before the 3S treatment and gradient layer properties after the 3S treatment. Results show that 316 stainless steel has a higher work-hardening capacity compared to the TC4 alloy before the 3S treatment; the maximum microhardness increment ratio, thickness of gradient layer and surface strengthening energy are also higher, and surface strengthening exponent is lower in the 316 stainless steel compared to the TC4 alloy after the 3S treatment. In addition, the exponential relation between the maximum microhardness increment ratio and work-hardening exponent, the exponential relation between the thickness of gradient layer and work-hardening exponent, the power function relation between the surface strengthening exponent and work-hardening exponent, and the linear relation between the surface strengthening energy and surface strengthening exponent are studied, respectively. Based on the above results and analysis, the microhardness distributions of gradient layer were discussed based on the work-hardening capacity, and the effects of the work-hardening capacity of the as-received metallic materials on the gradient layer properties of the surface strengthened metallic materials were summarized.