H13钢表面激光熔覆层稀释率及强化效果研究

摘要

In order to improve surface performance of H13 steel, Ni-based coatings were fabricated on H13 steel surface with YLS-4000 fiber laser.On the basis of orthogonal test and analysis, superficial status, geometric parameters, dilution ratio, microstructure and hardness of coatings under different processing parameters were obtained and investigated.The results show that coating surface is uneven when laser power is minimum (1800W) and powder feeding rate is maximum (1.0g/s).Coating surface has cracks when laser power (2200W) and scanning speed (25mm/s) are maximunm.When dilution ratio is lower than 10%, average hardness of cladding zone is improved to more than 800HV and is more than 3 times of substrate hardness (246HV).Strengthening effect is remarkable.When dilution ratio is larger than 25%, hardness of bottom layer in cladding zone is low due to the dilution of substrate.With the increase of laser power and scan speed, dilution ratio of the coating increases while dilution ratio decreases with the increase of powder feeding rate.Coatings of good quality with smooth surface, compact texture, and remarkable strengthening effect can be obtained by adjusting processing parameters.%为了改善H13钢的表面性能,利用YLS-4000型光纤激光器在H13钢表面熔覆镍基涂层,采用正交试验法,对不同工艺下的熔覆层表面形貌、几何参量、稀释率、微观组织、显微硬度进行了检测分析.结果表明,激光功率最小而送粉速率最大时(P=1800W,vf =1.0g/s)表面凹凸不平;激光功率和扫描速率最大时(P=2200W,vs=25mm/s)表面出现裂纹;当稀释率η＜10%时,熔覆区平均硬度(大于800HV)为基体硬度(246HV)的3倍以上,强化效果显著;当稀释率η＞25%时,熔覆区下部受熔化基体的稀释作用硬度较低;稀释率随着激光功率与扫描速率的增加而增加,随着送粉速率的增加而降低.通过调整工艺参量可获得表面平整光滑、组织致密、强化效果显著的熔覆层.