(1. 海军航空工程学院 青岛分院，青岛 266041；
2. 东北大学 材料与冶金学院，沈阳 110004)
摘 要: 为研究激光熔覆技术修复某定向凝固航空叶片，采用Nd:YAG激光在定向凝固DZ22基体表面熔覆镍基合金粉末，研究在常温非真空环境中激光熔覆定向凝固的结晶取向与性能。结果表明：工艺参数为扫描速度8~10 mm/s、电流100~140 A、脉宽6~8 ms及频率12~19 Hz时，在定向凝固基材DZ22的择优取向上，可以得到一次枝晶发达、无二次枝晶臂、无横向晶界的定向凝固熔覆层组织。枝晶的横向宽度为4~8 μm。沿扫描速度方向，在不同的工艺参数下可以得到不同的熔覆层宏观形貌。在定向凝固基材DZ22(100)面和非定向凝固基材GH710上，选择相同的工艺参数和工作环境，熔覆层晶粒生长无明显的方向性，没有实现熔覆层晶粒定向生长。熔覆层显微硬度明显提高，在熔覆层表面附近硬度达到最大值，约为450HV。熔覆层的磨损量明显小于基材的磨损量，为基材磨损量的50%~60%。熔覆层以磨粒磨损为主，磨损表面分布着一些犁削沟。
关键字: 镍基合金；激光熔覆；定向凝固；择优取向；晶界强化；摩擦；磨损
（1. Qingdao Branch of Navel Aeronautical Engineering Institute, Qingdao 266041, China;
2. School of Materials and Metallurgy, Northeastern University, Shenyang 110004, China）
Abstract:To repair a directionally solidified aero blade, laser cladding on DZ22 substrate using Ni-based alloy powder by Nd:YAG laser was carried out. The crystal orientation and performance of directional solidification of laser cladding in the open and normal temperature environment were researched. The results show that the directional solidification cladding layers on the preferred orientation of DZ22 substrate are obtained when the technological parameters are scanning speed of 8-10 mm/s, electric current of 100-140 A, pulse width of 6-8 ms and frequency of 12-19 Hz. There are developed first dentrites with no secondary branches and transverse grain boundaries. The transverse width is 4-8 μm. Different cladding layer macro-morphologies are gotten along the scanning direction at different technological parameters. The growth direction of the cladding layer grains is not clear on the (100) surface of DZ22 substrate and the non-directional solidification of GH710 of the same processing parameters and working environment. The cladding layer microhardness is improved obviously. The peak value of about 450HV is obtained near the surface of the cladding layer. The wear capacity of the cladding layer is obviously less than that of the substrate, which is 50%-60% of that of the substrate. The main abrasion form of the cladding layer is abrasive wear. There are some plough cut ditches on the surface of the cladding layer.
Key words: Ni-based alloy; laser cladding; directional solidification; preferred orientation; boundary strengthen; friction; wear
