FATIGUE STRENGTH IMPROVEMENT OF NORMALIZED 0.53 CARBON STEEL BY LASER SURFACE TREATMENT

Laser surface hardening is now being accepted as effective as other conventional hardening techniques, Laser beam provides the extra advantage of hardening localized region in intricate engineering component. Fatigue strength is a surface phenomenon, although factors such as microstructure and residual stresses affect the fatigue strength, surface condition if not favorably prepared is detrimental to the fatigue behavior. ND-YAG Laser pulses were applied to treated 0.53 carbon steel specimens. Microstructure was found to consist of martensite and cementite, however micro hardness up to 900 Hv and depth of hardening 0.9-1.0 mm was obtained due to laser treatment. Overlapping of laser pulses has result in low surface roughness and reduced surface micro-hardness scatter in the laser-affected zone. Laser treatment was found to be detrimental as far as rotating bending fatigue strength is concerned, the effect increases as the laser intensity increases, However if it is the favorable effect in improving the endurance limit (11%).