热处理工艺对Ni基合金复合涂层组织与性能的影响

Effect of Heat Treatment Process on Microstructure and Properties of Ni-based Alloy Composite Coatings

摘要:

激光熔化沉积制备的Ni基高温合金涂层会在涂层内部积累大量的残余应力，对涂层的组织与性能产生不利的影响。通过激光熔化沉积技术在304NG不锈钢基体上制备Nb和WC复合强化的4级Ni基高温合金涂层，通过退火处理降低涂层内部的残余应力。研究不同的退火温度和退火时间对涂层的微观组织、显微硬度、耐磨损性能和拉伸性能的影响规律。研究结果表明：退火温度的增加会导致涂层中较软的基体相γ-Ni含量增加，硬度下降，离散分布的共晶组织转变为连续分布的网状结构。综合分析，在700 ℃/1 h/炉冷处理后的涂层表现出最优异的耐磨损性能以及拉伸性能，因摩擦磨损产生的疲劳裂纹消失，磨损机制由疲劳磨损转变为磨粒磨损，同时在保证涂层耐磨损性能的同时，增强涂层的塑性，做到强塑性协同增强。

Abstract:

Ni-based superalloy coatings fabricated by laser melting deposition accumulate a large amount of residual stresses inside the coating, which adversely affects the microstructure and properties of the coating. The grade 4 Ni-based superalloy coatings reinforced with Nb and WC composite were prepared on 304NG stainless steel substrate by laser melting deposition technique, and the residual stresses inside the coatings were reduced by annealing treatment. The effects of annealing temperature and annealing time on the microstructure, microhardness, wear resistance, and tensile properties of the coatings were investigated. The results show that an increase in annealing temperature leads to an increase in the content of the softer matrix phase γ-Ni of the coating, a decrease in hardness, and the transformation of the discretely-distributed eutectic structure into a continuously-distributed network structure. Comprehensive analysis indicates that the coating after 700 °C/1 h/furnace cooling treatment exhibits the most excellent wear resistance and tensile properties. This is because the fatigue cracks generated during friction and wear in this coating disappear, and the wear mechanism transitions from fatigue wear to abrasive wear. At the same time, while ensuring the wear resistance of the coating, the plasticity of the coating is enhanced, achieving a synergistic enhancement of strength and plasticity.