Effect of Laser Shock Peening on Gas Carburizing for 18CrNiMo7–6 Gear Steel
MIAO Xiaoji1 , SONG Lu2 , MA Heng 2,3, GU Xiaoming3 , SUN Fei 1,2, HU Jing2
( 1. Institute of Modern Equipment Manufacturing, Changzhou Institute of Industry Technology, Changzhou 213164, China; 2. National Experimental Demonstration Center for Materials Science and Engineering, Changzhou University, Changzhou 213164, China; 3. Changzhou Tianshan Heavy Industry Machinery Co., Ltd., Changzhou 213019, China )
Abstract：18CrNiMo7–6 gear steel was selected as the material and laser shock peening was primarily used as a pretreatment prior to gas carburizing, the aim of which is to improve the efficiency and further enhance the properties after gas carburizing. Optical microscope, surface roughness tester and Vickers micro-hardness tester were used to investigate the surface characteristics after laser shock peening and gas carburizing. The results show that under the same gas carburizing process of 910℃+4h, gas carburizing efficiency can be effectively enhanced by the pretreatment of laser shock peening, the carburizing layer increases from 1.24mm to 1.49mm, and the carburizing efficiency increases by around 20%. At the same time, the surface hardness is increased from 680HV0.05 to 700HV0.05. Especially, laser shock pretreatment can make the cross sectional hardness gradient decreased gentlely, thus enhance the bonding force between carburized layer and matrix. The mechanism why laser shock peening has significant effect on gas carburizing is as below: the surface rough increases from 0.12μm to 0.57μm, a deformation layer with thickness of about 220μm was formed after laser shock peening, and with much finer grain size. All the above factors are beneficial for absorption and diffusion inward of carbon atoms.
2020, 
