Abstract
In order to clarify the effect of thermal sprayed (WC-Cr-Ni) cermet coating on the corrosion fatigue strength of high strength SKD11 steel, rotating bending corrosion fatigue tests were conducted in a 2 mass% ZnSO_4 aqueous solution. It was found that the corrosion fatigue strength of the thermal sprayed (WC-Cr-Ni) cermet coated specimen with 100μm thickness was 318.6MPa at 2×10^7 cycles and was about three times larger than that of the SKD11 base metal at the same number of cycles. Corrosion fatigue life tests were also conducted at rotating bending stress of 342.5 MPa on (WC-Cr-Ni) cermet coated specimen with coating thickness of 50 to 150μm to investigate the effect of coating thickness. It was found that the effective thickness of this coating was about 100 μm. The major cause of the improvement of corrosion fatigue strength by thermal sprayed (WC-Cr-Ni) cermet coating is the insulation of SKD11 steel from the permeation of ZnSO_4 aqueous solution. Impregnation of fluorine contained resin into the thermal sprayed (WC-Cr-Ni) cermet coating improved again corrosion fatigue strength at 2×10^7 cycles. However impregnation of fluorine-contained resin was ineffective at higher stress region due to the exfoliation from cermet coating.
