等离子喷涂Mo包覆Ni20Cr自粘结粉末制备的粘结层结合性能  

The Adhesive Strength of the Novel Bond Coat Deposited by Atmospheric Plasma Spraying using Mo-clad Ni20Cr Powders

作　　者：宋久泾 董昕远 田俊伟 雒晓涛[1] 李长久[1] Song Jiujing;Dong Xinyuan;Tian Junwei;Luo Xiaotao;Li Changjiu(State Key Laboratory for Mechanical Behavior of Materials,School of Materials Science and Engineering Xi'an Jiaotong University,Xi'an 710049)

机构地区：[1]西安交通大学材料科学与工程学院、金属材料强度国家重点实验室,西安710049

出　　处：《热喷涂技术》2022年第4期19-28,共10页Thermal Spray Technology

基　　金：国家自然科学基金重点项目(U1837201,52031010)。

摘　　要：针对如何提升金属粘结层结合强度的问题,本研究提出了使用Mo包覆Ni20Cr复合粉末作为新型粘结层材料的方法。高熔点Mo包覆层可以减少喷涂过程中核芯元素的蒸发,在大气等离子喷涂条件下获得超高温熔滴,有助于涂层与基体以及涂层内部实现冶金结合。采用机械合金化法制备了Mo包覆Ni20Cr复合粉末,并在大气等离子喷涂条件下制备涂层考察其结合强度。通过一维传热模型预测了镍基合金熔滴碰撞在镍基合金、奥氏体不锈钢和低碳钢基体上实现铺展熔合冶金自结合所需要的温度,采用DPV-2000测试系统对粒子飞行过程中的温度进行测量,使用扫描电子显微镜(SEM)对涂层的微观结构进行了表征。粒子温度测量结果表明,在大气等离子喷涂条件下,Ni20Cr-Mo熔滴可加热至2620℃以上,满足碰撞铺展过程中引起基体表面熔化而产生冶金结合的温度条件。涂层结合强度拉伸试验中所有试样都从胶中断裂,涂层结合强度大于76.1 MPa。组织观察结果表明涂层组织结构致密,不仅大量粒子层界面间产生了冶金结合,涂层与基体界面处也观察到一定深度的熔坑,表明涂层与基体以及涂层层间界面均实现了冶金结合,由此显著提高了结合强度。Many metal coatings are often used as bond coat to improve the adhesion of the thermal spray coatings to the substrate.However,their bonding strength to substrates is limited either by specific metallurgical bonding with the substrate or by low cohesive strength of the bond coat.Typically,such as Ni-clad Al composite powders and refractory metals,although a metallurgical bonding can be formed at the interface between the substrate and first splats intact to substrate,the bonding at the interfaces between splats is mainly dependent on mechanical interlocking.Therefore,the development of bond coat materials with both high adhesive strength and cohesive strength is of primary importance.In this study,Mo-clad Ni20Cr powders prepared by mechanical alloying are proposed as a novel bond coat material.Mo cladding suppresses the vaporization of both Ni and Cr when Ni20Cr is fully melted.Ni20Cr-Mo spray particles can be heated to a temperature higher than Mo melting point.The impact of the droplets of such high temperature can cause a mild steel substrate surface melting and consequently lead to the spread-fusing effect of substrate to create the metallurgical bonding with steel substrate.Moreover,the alloying of molybdenum to Ni-based alloy changes little thermophysical properties of bond coat materials,especially its melting point.As the result,the impact of Ni20Cr-Mo droplets on NiCrMo splat surface creates also the spread-fusing metallurgical bonding effect,ensuring sufficiently high cohesive strength.Furthermore,the deoxidizing effect of Mo cladding ensures limited oxide inclusion into bond coat during atmospheric plasma spraying which further ensures the cohesive bonding strength.In this study,the temperature at the interface between Ni20Cr-Mo droplet and substrate is calculated numerically by a one-dimensional heat transfer model for different substrates of Ni-based alloy,austenite stainless steel and mild steel to examine the droplet temperature requirement to create the spread-fusing metallurgical bonding.Atmosph

关 键 词：金属粘结层 结合强度 包覆粉末 镍基合金 冶金结合 大气等离子喷涂 

分 类 号：TG174.4[金属学及工艺—金属表面处理]