45钢激光硼氮合金化层制备及性能研究

Study on the Preparation and Properties of Laser Boron-Nitrogen Alloying Layer on 45 Steel

为了使得工程上常用的零部件保持自身韧性的同时提高其表面的耐磨性,利用激光合金化技术在45钢表面制备了二元硼氮合金化层,优化了工艺参数,研究了合金化层的组织及性能。结果表明:随激光功率、扫描速度、搭接率增大,合金化层硬度均呈先增后降的趋势,在1.5 kW、500 mm/min、50%时硬度分别达到最大值954,885,882 HV_(2N),随B∶N(质量比)中B的含量提高,合金化层硬度逐渐上升;最佳工艺参数为:激光功率1.5 kW,扫描速度500 mm/min,搭接率50%,经最优工艺处理后的合金化区组织由Fe_(2)N、Fe_(2)B、FeB、Fe_(7)C_(3)、γ-(Fe,N)等化合物和固溶体组成,以柱状晶和胞状晶为主,厚度约为600μm,平均硬度为1023 HV_(2N),热影响区组织由少量针状马氏体以及残余奥氏体等组成,厚度约为250μm,硬度由967 HV_(2N)到265 HV_(2N)呈梯度分布;合金化层的摩擦系数约为0.4519,磨损率为0.4231×10^(-14) m^(3)/(N·m),是基体的1/9左右,磨损机制为磨粒磨损并伴有黏着磨损。

In order to improve the wear resistance of the surface while maintaining the toughness of the commonly used parts in engineering,a binary-boron nitrogen alloying layer was prepared on the surface of 45 steel by laser alloying technology.The process parameters were optimized,and the microstructure and properties of the alloying layer were studied.Results showed that with the increase of laser power,scanning speed and lap ratio,the hardness of the alloying layer firstly increased and then decreased,and the maximum hardness was 954 HV_(2N),885 HV_(2N) and 882 HV_(2N) at 1.5 kW,500 mm/min and 50%,respectively.As the content of B in B:N(mass ratio)increased,the hardness of the alloying layer increased gradually;the optimal process parameters were 1.5 kW of laser power,500 mm/min of scanning speed,50%of lap rate.The microstructure of the alloying zone in the coatings treated by the optimal process was composed of Fe_(2)N,Fe_(2)B,FeB,Fe_(7)C_(3),γ-(Fe,N)and other compounds and solid solution,which were mainly columnar and cellular crystals with a thickness of about 600μm.Furthermore,the average hardness was 1023 HV_(2N),and the heat affected zone was composed of a small amount of acicular martensite and retained austenite with a thickness of about 250μm.The hardness distribution was gradient from 967 HV_(2N) to 265 HV_(2N).In addition,the friction coefficient of the alloying layer was about 0.4519,and the wear rate was 0.4231×10^(-14) m^(3)/(N·m),which was about 1/9 of that of the substrate.Besides,the wear mechanism was abrasive wear accompanied by adhesive wear.