(1. 海軍航空工程學院 青島分院，青島 266041；
2. 東北大學 材料與冶金學院，沈陽 110004)
摘 要: 為研究激光熔覆技術修復某定向凝固航空葉片，采用Nd:YAG激光在定向凝固DZ22基體表面熔覆鎳基合金粉末，研究在常溫非真空環(huán)境中激光熔覆定向凝固的結晶取向與性能。結果表明：工藝參數為掃描速度8~10 mm/s、電流100~140 A、脈寬6~8 ms及頻率12~19 Hz時，在定向凝固基材DZ22的擇優(yōu)取向上，可以得到一次枝晶發(fā)達、無二次枝晶臂、無橫向晶界的定向凝固熔覆層組織。枝晶的橫向寬度為4~8 μm。沿掃描速度方向，在不同的工藝參數下可以得到不同的熔覆層宏觀形貌。在定向凝固基材DZ22(100)面和非定向凝固基材GH710上，選擇相同的工藝參數和工作環(huán)境，熔覆層晶粒生長無明顯的方向性，沒有實現熔覆層晶粒定向生長。熔覆層顯微硬度明顯提高，在熔覆層表面附近硬度達到最大值，約為450HV。熔覆層的磨損量明顯小于基材的磨損量，為基材磨損量的50%~60%。熔覆層以磨粒磨損為主，磨損表面分布著一些犁削溝。
關鍵字: 鎳基合金；激光熔覆；定向凝固；擇優(yōu)取向；晶界強化；摩擦；磨損
（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
