Through the experimental study of laser melting and laser melting impact on gray cast iron, the changes of microstructure and properties of modified layer after laser action are analyzed in detail. Different experimental parameters are selected for comparison and optimized. The main conclusions are as follows:
(1) After optimizing the experimental parameters, the best laser melting power and laser scanning speed of gray cast iron are selected. When the laser power is 1500 W and the scanning speed is 5 mm / s, the melting layer of gray cast iron has better surface morphology and molten pool size. After laser melting of gray cast iron, the structure of the melting layer is composed of cementite and eutectic ledeburite. The graphite in the melting layer of gray cast iron is completely decomposed, and the structure is flake martensite and retained austenite in the heat affected zone. Part of the graphite in the heat affected zone is dissolved and the remaining graphite is refined. The hard cementite of the fusion layer of gray cast iron has extremely high hardness and wear resistance. Under the laser power of 1500 W and the scanning speed of 5 mm / s, the maximum hardness of the fusion layer of gray cast iron reaches 728 hv0 2, and the friction coefficient is 0.14, with small wear.
(2) After laser melting, the surface of gray cast iron melting layer is prone to crack under the action of residual tensile stress, and the crack propagates along the surface columnar crystal, resulting in the cracking of gray cast iron melting layer. The residual tensile stress of gray cast iron melting layer can be completely transformed into residual compressive stress by laser impact, which can effectively reduce the harm of surface cracking of gray cast iron melting layer. Laser shock leads to plastic deformation in a certain depth range of the fused layer, and the greater the laser power is, the deeper the deformation depth is. After laser shock, the cementite structure in the plastic deformation layer is refined and decomposed, and the ledeburite structure is deformed. The hardness of the plastic deformation area in the gray cast iron melting layer after laser shock is further increased. Under the laser shock energy of 3 J, the maximum hardness of the gray cast iron melting layer reaches 990 hv0 2。 The gray cast iron surface after laser melting and impact has good wear resistance, the lowest friction coefficient and the least wear, and the number of cracks on the sample surface is reduced after wear.