摘要
目的激光熔覆具有界面结合强度高和热影响区可控等特点,广泛应用于能源动力、航空航天等领域。熔覆过程在快速凝固下易形成Laves相和碳化物等硬脆相,从而降低了熔覆件的力学性能。为此采用固溶-时效热处理方法,优化激光熔覆IN625合金的显微组织和综合性能,为IN625熔覆件热处理方法提供工艺参考。方法通过设计固溶时效处理方案,研究固溶时效工艺参数对激光熔覆IN625 Laves相溶解及γ″强化相析出行为的影响规律,分析固溶时效对熔覆层硬度、耐磨性能的影响。结果采用1200℃固溶处理45 min,可实现Laves相的完全溶解,改善元素分布均匀性;采用650℃时效处理20 h,可以促使大量的γ″相析出,熔覆层的硬度提升至324HV0.2,相较于未处理试样,提高了17.1%;当时效温度升至750℃时,γ″相开始发生转变,经850℃时效处理后,基本转变为δ相,导致熔覆层的硬度和耐磨性下降。结论固溶温度的升高可促进激光熔覆IN625中Laves相的溶解和元素均匀化,但过高的温度(1300℃)将导致晶粒粗大。650℃低温时效有利于γ″相的析出,在析出强化作用下,可提升熔覆层的硬度和耐磨性。时效温度过高(850℃)将导致γ″相向δ相转变,进而降低熔覆层的性能。
Laser cladding has been extensively employed in the aerospace and power generation industries due to its precise energy control and strong metallurgical bonding capabilities.However,the rapid solidification inherent in the process often promotes the formation of brittle intermetallic compounds,such as Laves phases and carbides,which significantly degrades the mechanical properties of the deposited layer.The work aims to systematically investigate the effects of solution treatment and aging treatment on the microstructure and properties of laser cladded IN625.Particular attention was paid to the microstructural evolution mechanisms and their effect on hardness and wear resistance during heat treatment.In this investigation,an IN625 nickel-based superalloy substrate was coated with a laser-clad layer by a high-power diode laser.The effects of solution treatment at varying temperatures and aging treatment in the range of 650-850℃on the microstructural evolution and mechanical properties of the deposited layer were comprehensively analyzed.Optical microscopy(OM)was used to observe the macroscopic features of the cladded layer,while scanning electron microscopy(SEM)revealed detailed microstructural transformations.The coating's strength and wear resistance were evaluated through micro-indentation hardness testing and sliding wear analysis.A parametric study demonstrated that the solution treatment temperature significantly affected dendritic arm spacing,whereas aging duration regulated the redistribution of Laves phases.These factors collectively governed the hardness-toughness balance and provided an experimental foundation for optimizing the heat treatment process of laser cladded IN625 alloy.The results indicated that solution treatment at 1200℃for 45 min led to the complete dissolution of the original long-chain Laves phase in the cladded layer and promoted uniform distribution of alloying elements.During subsequent aging treatment at 650℃for 20 h,a significant amount of nano-scaleγ″phase(Ni3Nb)precipitated from the matrix,resulting in a marked increase in microhardness to 350HV0.2-approximately 16.7%higher than that of the as-cladded condition.However,as the aging temperature increased to 750℃,theγ″phase began to transform into a needle-likeδphase.This transformation became nearly complete after aging at 850℃,ultimately causing a notable reduction in the hardness of the cladded layer.These sequential phase transformations underscored the critical role of heat treatment temperature in governing the evolution and mechanical performance of precipitates in the laser-cladded IN625 alloy.The investigation confirms that higher heat treatment temperatures facilitate the decomposition of Laves phase structures in the cladded layer and significantly enhance the homogenization of alloying element distribution.During subsequent aging,a low-temperature condition of 650℃promotes the precipitation of a large quantity of nano-scaleγ″strengthening phases.These precipitates serve as effective barriers to dislocation motion,thereby markedly improving the mechanical strength of the cladded layer.However,when the aging temperature exceeds 750℃,the thermodynamically unstableγ″phase progressively transforms into a coarse,needle-likeδphase.This transformation gradually weakens the precipitation strengthening effect,ultimately leading to substantial degradation in mechanical performance.These findings offer theoretical guidance for optimizing the heat treatment process of laser-cladded IN625 alloy,suggesting that optimal microstructure-property relationships can be achieved through precise control of solution and aging parameters.
作者
姚喆赫
冯勇辉
陈健
隋永枫
董刚
张群莉
姚建华
YAO Zhehe;FENG Yonghui;CHEN Jian;SUI Yongfeng;DONG Gang;ZHANG Qunli;YAO Jianhua(Institute of Laser Advanced Manufacturing,Zhejiang University of Technology,Hangzhou 310023,China;Zhejiang Key Laboratory of High-Precision and Efficiency Hybrid Processing Technology and Equipment,Zhejiang University of Technology,Hangzhou 310023,China;College of Mechanical Engineering,Zhejiang University of Technology,Hangzhou 310023,China;Hangzhou Steam Turbine Power Group Co.,Ltd.,Hangzhou 310023,China)
出处
《表面技术》
北大核心
2025年第23期175-187,共13页
Surface Technology
基金
国家重点研发计划青年科学家项目(2023YFB4604300)
国家自然科学基金面上项目(52175443)
“尖兵领雁+X”研发攻关计划(2024C01178)。
关键词
激光熔覆
固溶处理
时效处理
显微硬度
耐磨性能
laser cladding
solution treatment
aging treatment
microhardness
wear resistance
