45钢表面激光熔覆WC增强Ni基涂层性能

Performance of WC Reinforced Ni-based Coating on 45 Steel Surface by Laser Cladding

为了利用激光熔覆技术实现模切机刀辊刀刃的增材制造,以激光功率、扫描速度、离焦量为影响因素,在45钢表面进行WC增强Ni基混合粉末的单道激光熔覆正交试验,制备单道激光熔覆梯度涂层,并对熔覆层的显微组织结构、缺陷率、残余应力以及显微硬度进行分析。由分析结果得出,熔覆层组织呈现出有利于改善熔覆层性能的明显分层;缺陷率随着扫描速度和离焦量的增大而增大,随着激光功率的增大先增大后减小,其中扫描速度对缺陷率有显著的影响;熔覆过程中熔覆层与基体之间的温度差以及熔覆层与基体之间热膨胀系数差异是产生残余应力的主要原因。各因素对残余应力的影响主次顺序为扫描速度>激光功率>离焦量。组织分层的结构有利于缩小熔覆层与基体的线膨胀系数差异;显微硬度从基体到熔覆层顶部呈阶梯状增长,熔覆层顶部的显微硬度可达到70 HRC,是基体的3～4倍,优于目前实际大规模使用中性能最优的进口粉末冶金硬质合金的模切机刀棍刀刃硬度(63 HRC)。

In order to utilize the laser cladding technology to achieve the additive manufacturing of the knife blade edge of the die-cutting machine,the laser power,scanning speed and defocusing amount are the influencing factors,and the single-pass laser cladding of WC-reinforced Ni-based mixed powder is performed on the surface of the 45 steel.The experiment was conducted to prepare a single-pass laser cladding gradient coating,and the microstructure structure,defect rate,residual stress and microhardness of the cladding layer were analyzed.According to the analysis results,the microstructure of the cladding layer shows obvious stratification which is conducive to improving the performance of the cladding layer.The defect rate increases with the increase of the scanning speed and the defocus amount,and increases first and then decreases with the increase of laser power.The scanning speed has a significant effect on the defect rate.The difference in temperature between the cladding layer and the substrate and the difference in thermal expansion coefficient between the cladding layer and the substrate during the cladding process are the main causes of residual stress.The influence of each factor on the residual stress is:scanning speed>laser power>defocusing amount.The structure of stratified layers helps to reduce the difference of linear expansion coefficient between the cladding layer and the substrate.The microhardness increases stepwise from the substrate to the top of the cladding layer.The microhardness of the top of the cladding layer can reach 70 HRC,which is about 3 to 4 times that of the substrate.It is superior to the actual performance of large-scale use of the imported powder metallurgy carbide die-cutting machine knife blade hardness (63 HRC).