Investigation of the rolling contact fatigue resistance of laser cladded twin-disc specimens: FE simulation of laser cladding, grinding and a twin-disc test

Rolling contact fatigue and wear damage of the surfaces of tribological components, such as roller bearings, gears, train wheels and rails, can be prevented by surface coating. Laser cladding is a welding process used for coating of surfaces. In this investigation, the laser cladding process and consecutive surface grinding of a twin-disc test specimen were simulated numerically using the finite element (FE) method. The disc was made of the pearlitic UIC grade 900A (R260) material and coated with a Co-Cr alloy. A non-linear isotropic and kinematic hardening model was used to simulate the material characteristics, and annealing material behaviour and phase transformation in the substrate material were also accounted for. Residual stress measurements were carried out for validation of the results from the FE simulations and there was good agreement. In addition, the influence of residual stresses on the safety margin against fatigue failure in a shakedown diagram was examined. It was carried out by comparison of two FE simulations of a twin-disc test: one simulation where the residual stresses from the surface treatment processes were incorporated, and one which was initially free from stresses. The multiaxial fatigue initiation criterion proposed by Dang Van was used in the fatigue evaluation. The results showed that the residual stresses caused by the surface treatment processes reduced the safety margin against fatigue failure in comparison with the initially stress-free FE simulation.