LaB_(6)颗粒对等离子堆焊Inconel625合金涂层显微组织和高温抗氧化性能的影响  

Effect of LaB_(6)on Microstructure and High-temperature Oxidation Resistance of Inconel625 Alloy Coating Fabricated by Plasma Transferred Arc Surfacing

作　　者：李景奎 王瑞超 潘琳琳 邹晓东 杨克 LI Jingkui;WANG Ruichao;PAN Linlin;ZOU Xiaodong;YANG Ke(School of Mechanical and Automation Engineering,Wuyi University,Guangdong Jiangmen 529020,China;Guangdong Provincial Key Laboratory of Material Joining and Advanced Manufacturing,China-Ukraine Institute of Welding,Guangdong Academy of Sciences,Guangzhou 510650,China)

机构地区：[1]五邑大学机械与自动化工程学院,广东江门529020 [2]广东省科学院中乌焊接研究所广东省材料连接与先进制造重点实验室,广州510650

出　　处：《表面技术》2025年第6期98-107,142,共11页Surface Technology

基　　金：广州市科技计划项目(2024A04J3442);江门市科技计划项目(2023780200040009603);江门市基础与理论科学研究类科技计划项目(2023JC01025,2023JC01006);广东省科技计划项目(2022A0505050052);国家重点研发计划项目(2020YFE0205300);广东省科学院发展专项资金项目(2020GDASYL-20200301001)。

摘　　要：目的为保证垃圾焚烧炉换热管在高温环境下的正常服役,常在换热管表面制备一层耐高温Inconel625(IN625)合金涂层,然而,随着换热管服役温度的不断增加,有必要提高IN625涂层的高温抗氧化性能,以提升换热管的使用寿命。方法在IN625合金中引入了1%(质量分数)平均粒径为5μm的LaB_(6)颗粒,并采用等离子堆焊技术制备了添加与未添加LaB_(6)颗粒的IN625和IN625/LaB_(6)涂层,随后对2种涂层取样,分别评价其微观组织、硬度以及在1000℃下的高温抗氧化性能。结果IN625样品为典型的柱状晶结构,随着La B_(6)颗粒的添加,IN625/LaB_(6)样品转变为柱状晶和等轴晶的混合结构,并且IN625/LaB_(6)样品中析出相明显增多,主要包括树枝状的Laves相和La-Ti-O复合氧化物等,细小弥散分布的La-Ti-O复合氧化物可以起到高温下阻碍晶粒生长的作用,从而细化晶粒,其显微硬度明显提升,从225.7HV0.3增加到268.92HV0.3。此外,在1000℃高温抗氧化实验条件下,晶粒的细化使IN625/LaB_(6)样品在氧化时有更多的Cr通过晶界运输到氧化界面形成致密的氧化膜,并且由于氧化界面附近Cr的大量消耗提高了Nb的活度梯度,促进了Nb向外扩散,在氧化膜/基体界面处形成了连续均匀的δ-Ni_3Nb层,并在氧化膜表面形成了更多的CrNbO_4,二者可以作为高温氧化期间阳离子和阴离子的扩散屏障。除此之外,一些在晶界析出的La-Ti-O复合氧化物会阻碍Ni、Fe和Nb等阳离子向外输运,从而避免了多种氧化物形成的生长应力使氧化层剥落,其氧化常数由(72±4)×10^(-2)mg^(2)/(cm^(4)·h)降低到(26±3)×10^(-2)mg^(2)/(cm^(4)·h)。结论LaB_(6)颗粒的添加促进了等离子堆焊IN625合金中部分柱状晶向等轴晶组织的转变与晶粒细化,提升了涂层的硬度,大幅改善了IN625合金在1000℃下的高温抗氧化性能。To ensure the security of heat exchanger tubes in garbage incinerators under high-temperature conditions,it is common to prepare a high-temperature-resistant coating on the surface of the heat exchanger tubes.Nickel-based superalloys,due to their excellent mechanical properties,oxidation resistance,and thermal stability at elevated temperatures,are considered a favorable choice for protective coatings on the heat exchanger tubes.However,due to the coarse microstructure resulting from PTA surfacing and its potential impact on the high-temperature performance of the coating,it becomes necessary to enhance the high-temperature oxidation resistance of the IN625 coating to extend the service life of the heat exchanger.In this study,1wt.%LaB_(6)particles with an average particle size of 1μm were introduced into the IN625 alloy.After that,the IN625 and IN625/LaB_(6)coatings with and without LaB_(6)particles were fabricated by plasma transferred arc(PTA)surfacing.Subsequently,the microstructure,hardness,and high-temperature oxidation resistance of the two coatings at 1000℃were evaluated.The IN625 sample exhibited a typical columnar grain structure.With the addition of LaB_(6)particles,the microstructure of IN625/LaB_(6)sample transformed into a mixed structure of columnar and equiaxed grains.Notably,the IN625/LaB_(6)sample showed increased precipitation of phases,including dendritic Laves phases and La-Ti-O composite oxides.The fine dispersed La-Ti-O composite oxides acted as inhibitors of grain growth at high temperature,resulting in refined grain size and significantly improving microhardness(increasing from 225.7HV0.3 to 268.92HV0.3).Furthermore,during the initial stage(first 50 h)of 1000℃high-temperature oxidation,the oxidation kinetics curves for both samples followed the parabolic law,although the IN625/LaB_(6)sample exhibited a lower oxidation rate.After 50 h oxidation,the oxidation constant of IN625 sample increased significantly from(14±1)×10^(−2)mg^(2)/(cm^(4)·h)to(72±4)×10^(−2)mg^(2)/(cm^(4)·h),

关 键 词：等离子堆焊 INCONEL625合金 LaB_(6) 高温抗氧化性能 La-Ti-O复合氧化物 晶粒细化 

分 类 号：TG174[金属学及工艺—金属表面处理]