Laser cavitation peening of gray cast iron: Effect of coverage layer on the surface integrity

Copper coverage layer was employed to the laser cavitation peening (LCP) of HT200 gray cast iron. The process of bubble evolution, velocity field of bubble, impact of water-jet, deformation and stress of material were simulated. The effects of coverage layer on the surface integrity (surface morphology and roughness, residual stress, micro-hardness) of LCP treated HT200 under various laser energies and defocusing amounts were systemically investigated. The results indicate that the maximum velocity of water-jet is 380 m/s and the diameter is 0.1 mm. The surface roughness of HT200 increases after the treatment of LCP. The presence of Copper coverage layer makes the HT200 surface more flat and the surface roughness decreases by half. At the case of no coverage layer, the parameters of 200 mJ laser energy and 1 mm defocusing amount are optimal for roughness, compressive residual stress and micro-hardness. Higher laser energy produces higher magnitude of micro-hardness and compressive residual stress in the case of coverage layer, and the optimal defocusing amount is 0 mm. © 2020