Effects of electroless deposition and shot peening on fatigue strength of 3OCrMo4 steel

Electroless nickel coatings cause a marked decrease in the fatigue strength of the base steel. For the 30CrMo4 steel used in the present work, the fatigue limit is reduced by electroless deposition by 39, 52, and 55% for heat treatment conditions of 200°Cfor 1 h, 400°C for 1 h, and 600°C for 3 h, respectively. Shot peening before deposition can increase the fatigue strength for material heat treated at 200 and 400°C, but reduces the fatigue strength for material heat treated at 600°C. Under all conditions, the loss of fatigue strength is primarily due to the poor fatigue properties of the coating and the weak interface between the coating and the substrate. The main factors which affect the fatigue properties of coated samples are the coating ductility, the interface bonding, and the residual stress within the coating. MST/3123