激光功率对CoNiCrAlY熔覆涂层显微组织及硬度的影响
Microstructure and Hardness of CoNiCrAlY Coatings on Titanium Alloy by Laser Cladding with Different Laser Power
王涛，刘佳奇，秦令超
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作者单位：中国民航大学航空工程学院
中文关键字：激光功率； CoNiCrAlY涂层； 显微组织； 显微硬度； 结合区域
英文关键字： laser power; CoNiCrAlY coating; microstructure; micro hardness; transition region
中文摘要：利用激光熔覆技术在Inconel 718镍合金基体上制备了CoNiCrAlY高温防护涂层。采用扫描速度7 mm/s，光斑直径4 mm，研究激光功率对CoNiCrAlY熔覆涂层宏观形貌、截面组织以及显微硬度的影响。实验结果表明，在相同扫描速度和光斑直径的条件下，熔覆层的宏观形貌在激光功率1800 W质量最优，熔覆层表面连续且平整，波浪起伏较小；随着激光功率的增加，激光能量增加，熔覆层的几何尺寸增大；当激光功率1400 W时，气体未完全逸出熔池就冷却凝固，涂层顶部出现气泡、孔隙等缺陷，当激光功率增加到2200 W时，不再出现明显的气泡和孔隙；随着激光功率的增加，熔覆材料吸收的能量越来越多，导致晶粒长大，熔覆层呈现柱状晶高度越来越大，树枝晶越来越多而胞状晶越来越少的组织形态。当激光功率为1800 W时，熔覆层整体形貌和组织的质量最好，熔覆层与基体结合紧密，没有熔渣或孔隙，形成了性能良好的冶金结合，平均显微硬度最高。
英文摘要：To improve the high temperature resistance of Inconel 718 substrate, CoNiCrAlY coatings were fabricated by the laser cladding. The influences of laser power on surface morphology, microstructure of cross section and hardness of CoNiCrAlY coatings were investigated under the same scanning speed 7 mm/s and diameter of spot 4 mm. The results showed that under the laser power 1800 W, the macro-morphology of coating had the best quality, and the coatings were continuous and smooth with small waves. With the laser power going up, the geometry size of cross section of coatings increased gradually due to that laser energy are absorbed. Under the laser power 1400 W, the defects such as bubbles and pores appeared at the top of the cladding layer due to that the molten liquid was cooled and solidified before the inclusion gas were escaped. Under the laser power 2200 W, no longer appeared bubbles and pore. With the increase of laser power, the energy absorbed by the cladding layer increases, which leads to grain growth. Therefore, the columnar crystals at the cladding layer were higher, dendrites were more and cellular crystal less. Under the laser power 1800 W, the quality of the overall morphology and microstructure of the cladding layer was best and the average micro-hardness was most high. At the same time, the cladding layer and the substrate were closely bounded and formed a firm metallurgical combination with no slag and air voids.