蠕墨铸铁激光熔覆镍基合金工艺及性能表征

Laser cladding process and performance of Ni-based alloys coating on compacted graphite cast iron

为了提高蠕墨铸铁玻璃模具的使用寿命,采用激光熔覆的方法,在模具表面熔覆一层镍基合金涂层。研究激光功率、扫描速度、送粉量和搭接率等对涂层组织结构的影响,利用扫描电子显微镜(SEM)、光学显微镜(OM)和X射线衍射分析仪观察和分析不同工艺参数下熔覆层表面和截面形貌以及物相结构,并以熔覆层是否存在气孔、裂纹等缺陷以及组织形貌特征来确定最佳工艺参数,并对最佳工艺下获得的多道单层熔覆层进行硬度和摩擦磨损测试。结果表明:(1)激光熔覆镍涂层的最佳工艺参数为:功率800W、扫描速度3mm/s、送粉量5.4g/min、搭接率25%。(2)最优参数下获得的熔覆层的物相主要为γ-(Fe,Ni)和Cr_(23)C_6。涂层平均硬度为389.9HV,是基体的2.48倍。涂层摩擦系数曲线较平缓、波动较小,值约为0.38,比基体下降了0.25。在100N载荷下涂层和基体的磨损率分别为1.72×10^(-6)和7.15×10^(-6)g/m。

Ni-based alloys was coated on compacted graphite cast iron surface to prolong the working life of glass mold by laser cladding method.Research the impacts of laser power,scanning speed,powder feed rate and over lap rate on the cladding layer organization structure.Coating surface,cross section morphology and phase constitution were studied through scanning electron microscope （SEM）,optical microscopy （OM） and XRD.Optimum parameters were confirmed by defects such as pore,crack and micro-structures.The hardness and frictional wear of multi-channel single cladding layer were tested under optimum parameters.The results show that： （1） Optimum parameters of cladding Ni-based alloy on mold surface include laser power of 800 W,scanning velocity of 3 mm/s,feed rate of 5.4 g/min and the overlapping ratio of 25%.（2） Experimental results show that γ- （Fe、Ni） and Cr（23）C（63） are the main phases in the coating of optimum parameters.The average hardness of the coating is 389.9 HV which is 2.48 times of that of the substrate.The friction coefficient of coating is 0.38,decreased by 0.25 compared to the substrate,and the friction coefficient curve is gentle and less volatile.The wear rate of coating and substrate was 1.72 ×10～（-6） g/m and 7.15 ×10～（-6） g/m under a load of 100 N.