45钢激光碳硼合金化工艺优化及最优工艺下合金化层的组织与性能

Optimization of Laser Carbon-Boron Alloying Process for 45 Steel and Microstructure and Properties of Alloying Layer Under Optimal Process

采用激光合金化法在45钢表面制备了碳硼二元合金化层,通过正交试验对其工艺进行优化,并研究了最优工艺下合金化层的组织与性能。结果表明:正交试验得到最优工艺为激光功率2.2 kW,扫描速度500 mm·min^(-1),搭接率40%,硼、碳粉末质量比6.0∶3.5;最优工艺下制备的合金化层由Fe_(3)C、Fe_(2)B、FeB、γ-(Fe,C)相组成,包括合金化区和热影响区;合金化区组织以柱状晶和胞状晶为主,其厚度约为600μm,平均硬度为879 HV,热影响区组织由针状马氏体和残余奥氏体组成,其晶粒尺寸由基体向合金化区逐渐变小,热影响区厚度约为450μm,硬度在220~768 HV间呈梯度分布;合金化试样的摩擦因数约为0.4666,磨损率为0.4553×10^(-14) m^(3)·N^(-1)·m^(-1),与45钢基体试样相比,耐磨性能得到大幅提高。

The carbon-boron binary alloying layer was prepared on the surface of 45 steel by laser alloying process.The process was optimized by orthogonal test,and the microstructure and properties of alloying layer under the optimal process were studied.The results show that the optimal process obtained by orthogonal test included laser power of 2.2 kW,scanning speed of 500 mm·min^(-1),overlap rate of 40%,and mass ratio of boron and carbon powder of 6.0∶3.5.The alloying layer prepared under the optimal process was composed of Fe_(3)C,Fe_(2)B,FeB andγ-(Fe,C)phases,and consisted of alloying zone and heat affected zone.The microstructure of alloying zone was mainly columnar and cellular crystals,with a thickness of about 600μm and an average hardness of 879 HV.The microstructure of heat affected zone was composed of acicular martensite and retained austenite,and its grains gradually became smaller from the matrix to the alloying zone.The thickness of heat affected zone was about 450μm,and the hardness presented gradient distribution between 220-768 HV;The friction coefficient of alloying layer sample was about 0.4666 and the wear rate was 0.4553×10^(-14) m^(3)·N^(-1)·m^(-1);compared with 45 steel matrix sample,the wear resistance was greatly improved.