Fatigue behavior of laser clad round steel bars

Laser cladding is an overlay welding method to manufacture high performance, fusion bonded metal, and metal matrix composite coatings on metallic substrates with low dilution. Owing to steep thermal gradients, rapid solidification, and possible mismatch in coefficients of thermal expansion between the coating and the substrate, laser cladding induces large tensile residual stresses in coating layer, potentially affecting the service life of clad component under external load-induced stresses. In this study, four-point bending and torsion fatigue tests were conducted on relatively large round laser clad steel bars to determine the effect of laser cladding on fatigue strength. Quenched and tempered 42CrMo4 steel clad with Inconel 625 and S355 structural steel clad with Stellite 21 were subjected to various stress levels for relatively large number of cycles with and without postweld heat treatment (PWHT). The results indicated that Stellite 21 decreased the fatigue life of S355 at all the applied loads, whereas Inconel 625 increased the fatigue life of 42CrMo4 at high loads but decreased at low loads. Applied PWHT did not show any positive influence on fatigue life.