THE EFFECT OF COATING RESIDUAL-STRESS ON THE FATIGUE LIFE OF THERMAL SPRAY-COATED STEEL AND ALUMINUM

The acceptance of thermal spray coatings in many applications depends on the effect of the coating on the fatigue performance of the coated part. One of the factors that influences the fatigue life of thermal s pray-coated components is the residual stress in the coating. This stu dy investigates the fatigue performance of tungsten carbide-cobalt (WC -Co) thermal spray coating systems. Bending fatigue tests of specimens with WC-Co coatings on both 4130 steel substrates and 6061 aluminum s ubstrates were conducted. The through-thickness residual stress level in the thermal spray coatings was determined using the modified layer removal method. The effect of the residual stresses on the fatigue lif e of the coated specimens was analyzed. It was found that there is a d irect relation between the residual stress in the coating and the fati gue life of the coated part. Fatigue life can be changed by a factor o f ten due to the level of compressive residual stress in the coating. (C) 1998 Elsevier Science S.A. All rights reserved.