Study On The Microstructure And Properties Of Laser Surface Quenching For Ductile Cast Iron QT600-3

Ductile cast iron has an excellent performance, which is widely used inindustrial production. In order to improve the service life of the workpieces of ductilecast iron, it is necessary to investigate the surface treatment of ductile cast iron. Inthis paper, the specimens of ductile cast iron QT600-3were hardened by laser surfacequenching treatment. And the results were analyzed which could draw some usefulconclusions.The temperature field of ductile cast iron QT600-3during laser surfacequenching treatment was analyzed by ANSYS-a finite element analysis software. Thedepths of the hardened layer were predicted based on the analysis of the temperaturefield. The simulate results were compared with the experimental results of thehardened layer depths. It was found that the results of numerical simulations andexperiments were in good agreement under the same process parameters of lasersurface quenching.Laser surface quenching of ductile cast iron QT600-3was investigatedexperimentally by using a semiconductor laser unit. The micro-hardness, themicrostructure and the depths of the hardened layer of ductile cast iron QT600-3under different process parameters were mainly analyzed. The experimental resultsshow that great amounts of acicular martensites are obtained in the hardened zone.The hardness of the hardened surface could reach up to61HRC, which is about2-3times as high as that of the matrix. It was also found that, the depths of the hardenedlayer in the laser surface quenching treatment increase with the increase of laserpower, decrease with the increase of the scan rate, and decrease with the increase ofthe laser spot diameter.The wear test was carried on to analyze the wear resistance of the specimenshardened by the semiconductor laser surface quenching. The test results showed thatthe wear loss of the specimen hardened by the semiconductor laser surface quenchingis6%-18%of the amount of the specimen which was hardened by traditionalquenching process. Through the analysis of the morphology and friction coefficient ofthe specimens, it was found that the hardened layer obtained by the semiconductor laser surface quenching can get better wear resistance.