粉末中C抑制FeAl熔滴氧化机制及其对等离子喷涂层组织与性能的影响  

Mechanism of Suppressing Oxidation of FeAl Molten Droplet by Adding C to Powder and Its Effect on Microstructure and Properties of Plasma-sprayed Coating

作　　者：周哲 张黎 董昕远 雒晓涛[1] MAHRUKH M 李长久[1] ZHOU Zhe;ZHANG Li;DONG Xinyuan;LUO Xiaotao;MAHRUKH M;LI Changjiu l(State Key Laboratory for Mechanical Behavior of Materials,Xi'an Jiaotong University,Xi'an 710049,China;Department of Mechanical Engineering,NED University of Engineerig and Technology,Pakistan)

机构地区：[1]西安交通大学金属材料强度国家重点实验室,西安710049 [2]NED工程技术大学机械工程系,巴基斯坦

出　　处：《中国表面工程》2023年第1期44-56,共13页China Surface Engineering

基　　金：国家自然科学基金重点(U1837201,52031010);国家科技重大专项(2019-VII-0007-0147)资助项目

摘　　要：大气等离子喷涂(APS)金属时,熔滴不可避免地发生氧化是难以获得粒子间结合充分的致密涂层的主要原因。以FeAl金属间化合物为例,提出一种在粉末中添加亚微米金刚石颗粒引入碳源,以期利用碳在高温下优先氧化的特性抑制等离子喷涂飞行粒子中Fe、Al元素的氧化,获得无氧化物的高温熔滴从而制备低氧含量(质量分数)、粒子间充分结合的FeAl金属间化合物涂层的新方法。采用APS制备Fe Al涂层,研究金刚石的添加对涂层氧含量、碳含量、涂层内粒子间结合质量与硬度的影响规律,探讨FeAl熔滴飞行中的氧化行为。采用商用热喷涂粒子诊断系统测量APS喷涂中的粒子温度,通过SEM与XRD表征了涂层的组织结构,并表征涂层的结合强度与硬度。结果表明,在等离子射流的加热和Fe、Al元素放热反应的联合作用下,飞行中FeAl熔滴的表面温度可达2 000℃以上,满足C原位脱氧的热力学条件。与不含碳的传统Fe Al涂层中的氧含量随喷涂距离的增加而显著增加的规律完全不同,用Fe/Al/2.5C粉末喷涂时涂层中的氧含量随距离的增加而减小,表明飞行中熔滴的氧化得到抑制,实现了C原位脱氧抑制金属元素氧化的自清洁氧化物的效应。FeAl/2.5C涂层氧含量由传统FeAl涂层的3.67 wt.%显著降至0.62 wt.%以下,涂层中有限的氧化物主要来源于粒子沉积后氧化。因Fe Al/2.5C熔滴温度超过2 100℃,实现了熔滴碰撞引起同质涂层粒子表面熔化的自冶金结合效果,提升了涂层的致密性,其表观孔隙率由2.2%降至0.28%;涂层结合强度高于59.2 MPa,且因涂层由FeAl相及Fe3AlCx渗碳体相组成,其硬度达到590 HV0.3,约为传统Fe Al涂层的2倍。The severe oxidation of metal elements leads to a large amount of oxide inclusions that hinder the formation of metallurgical bonds across intersplat interfaces during thermal spraying in an ambient atmosphere,which further degrades the performance of thermally sprayed metal coatings.Controlling the oxidation of metal elements during spray deposition remains a significant challenge.In this paper,the thermodynamic and kinetic requirements of in-situ in-flight deoxidation by adding deoxidizer elements(diamond particles)to Fe/Al spray powders to achieve oxide-free molten droplets in an ambient atmosphere were investigated.Fe/Al/2.5C composite powders containing 2.5wt.%diamond particles were prepared by mechanical alloying.Atmospheric plasma spraying(APS)was used to generate an oxide-free molten spray of FeAl particles at temperatures higher than 2000°C.This was achieved by the in-situ self-oxide cleaning effect of in-flight particles by carbon,which prevented metal droplets from oxidizing in an open atmosphere.For comparison,a FeAl coating was also deposited using Fe/Al composite powders prepared by mechanical alloying.The particle velocity and temperature were measured by a commercial thermal-spraying particle diagnostic system.The microstructures of the coatings were characterized by scanning electron microscopy and X-ray diffraction.The chemical compositions of the coatings were measured by inductively coupled plasma spectroscopy.The adhesive strength and hardness of the plasma-sprayed FeAl-based coatings were tested.The results show that under the combined effects of plasma-jet heating and the FeAl exothermic reaction,the heated FeAl spray particles could reach a high temperature of over 2100 C,which meets the thermodynamic conditions for carbon in-situ deoxidation.Because oxidation occurs from the surface of an in-flight molten droplet,to maintain continuous deoxidation of the molten FeAl droplet,the rapid transfer of carbon from the interior of the molten droplet to the surface is necessary.It was confirmed t

关 键 词：大气等离子喷涂 FeAl/2.5C涂层 组织与性能 原位脱氧 自冶金结合 

分 类 号：TG174[金属学及工艺—金属表面处理]