45钢表面C22镍基合金激光熔覆层的制备与性能

Preparation and Properties of C22 Nickel-Based Alloy Laser Cladding Coating on 45 Steel Surface

应用激光熔覆技术在45钢基体表面制备C22镍基合金熔覆层,研究了激光功率(1 250~2 000 W)、扫描速度(80,130 mm·s^(-1))对熔覆层质量的影响,并获得最优工艺参数;分析了最优工艺参数制备熔覆层的物相组成、微观结构和耐腐蚀性能。结果表明:不同工艺参数下制备的熔覆层与基体均形成良好的冶金结合。随着激光功率的增加或扫描速度的降低,熔覆层宽度以及热影响区深度均整体呈增大趋势;随激光功率增大,80 mm·s^(-1)扫描速度下的熔覆层高度整体呈增大趋势,而130 mm·s^(-1)扫描速度下则整体呈减小趋势;130 mm·s^(-1)扫描速度下的熔覆层宽度和高度以及热影响区深度均较小。最优激光熔覆工艺参数为扫描速度80 mm·s^(-1)、激光功率1 750 W,此时单道单层熔覆层的高度最大,熔覆层宽度和热影响区深度适宜。熔覆层由γ-Ni(Cr,Mo,Fe)枝晶和少量Mo Ni4金属间化合物组成,钼元素在枝晶间富集;与介质温度为50℃时相比,介质温度为70℃下的熔覆层自腐蚀电位较低,自腐蚀电流密度较高,钝化膜电阻较低,耐腐蚀性能较差,但极化曲线中仍然存在稳定的钝化区,说明在该温度下仍具有较好的保护作用。盐雾加速腐蚀144 h后,熔覆层表面形貌未发生改变,耐腐蚀性能良好。

A C22 nickel-based alloy cladding layer was prepared on the surface of 45 steel for bolts by laser cladding technique.The effects of laser power(1250‒2000 W)and scanning speed(80,130 mm·s^(−1))on the quality of the cladding layer were investigated,and the optimal process parameters were obtained.The phase composition,microstructure,and corrosion resistance of the cladding layers prepared with optimal process parameters were analyzed.The results show that the metallurgical bonding was formed between the cladding layer prepared by different processes and the substrate.With the increase of laser power or the decrease of scanning speed,the width of cladding layer and the depth of heat affected zone increased basically.With increasing laser power,the height of cladding layer increased at the scanning speed of 80 mm·s^(−1),but decreased at the scanning speed of 130 mm·s^(−1).At the scanning speed of 130 mm·s^(−1),the width and height of cladding layer and the depth of heat affected zone were smaller.The optimal laser cladding parameters were the scanning speed of 80 mm·s^(−1) and the laser power of 1750 W.Under this optimal process,the height of the single-pass single-layer cladding layer was the biggest,and the cladding layer width and the heat affected zone depth were suitable.The cladding layer was composed ofγ-Ni(Cr,Mo,Fe)dendrites and a small amount of MoNi4 intermetallic compound and molybdenum was enriched in the interdendrite.Compared with the medium temperature of 50℃,the free corrosion potential of the cladding layer under the medium temperature of 70℃ was lower,the free corrosion current density was higher,the passivation film resistance was lower,and the corrosion resistance was poorer.However,there was still a stable passivation zone in the polarization curves,indicating that the protection was still excellent at 70℃.After accelerated corrosion by salt spray for 144 h,the surface morphology of the cladding layer did not change,indicating that the cladding layer had good corrosion resistance.