HVOF制备MCrAlY涂层过程中WC杂质颗粒的演变遗传行为研究
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摘要
在热喷涂工业生产过程中,喷涂制备不同材料体系的涂层之前需要对送粉路径(送粉罐、送粉盘、搅拌器、送粉管路、送粉针)进行清理,但由于送粉路径内部结构复杂且存在静电吸附效应,使得残留于喷涂系统的粉末无法被完全去除,通常以微量杂质颗粒的形式被带入新涂层,进而影响新涂层的性能。为此,本文研究了在单晶基材表面采用高速火焰(HVOF)喷涂制备MCrAlY涂层过程中,送粉路径残留的WC杂质颗粒(WC-10Co4Cr)在涂层及涂层与基材界面处的遗传演变行为,分别采用SEM、EDS分析了WC杂质在喷涂态、热处理态涂层中的微观组织和相组成。研究结果表明,WC杂质颗粒确实存在于MCrAlY涂层中,并在后期热处理及氧化试验中进一步分解而固溶于涂层中,甚至扩散至单晶基材内部引起含W碳化物的生成,影响涂层及单晶基材的显微组织,改变局部的成分均匀性。同时,本文还采用ThermoCalc软件进行了热力学计算模拟,辅助分析了WC分解及W与C元素在显微组织中的遗传特性。对于WC类粉末和MCrAlY粉末共用的HVOF喷涂设备,建议给MCrAlY粉末配备单独的送粉路径,以确保涂层的纯净度与质量。
In industrial thermal spray production processes, the workshop and route of powder feeding system needs to be cleaned when changing spraying materials. The powder feeding system include powder feeding tank,powder feeding tray, stirrer, powder feeding pipeline, powder feeding needle. Due to the internal structure of the powder feeding system is complex and the electrostatic adsorption effect, the residual powder in the spray system cannot be completely removed and thus affects the properties of the coating. In this paper, the high-velocity oxyfuel(HVOF) spray technology were adopted to prepare the MCrAlY coatings on the surface of single crystal substrate, the hereditary behavior in the coatings and the interface between coating and substrate of WC impurity particles(WC-10 Co4 Cr) remaining in the powder feeding system was studied. The microstructure and phase composition of WC impurities in spray and heat treatment coatings were analyzed by SEM and EDS. The results showed that WC impurity particles exist in the MCrAlY coatings and would be dissolved into coating and even diffuse into single crystal substrate to form new W carbides during heat treatment and oxidation processes. As a result, the microstructure of coating and single crystal substrate has been affected and the local composition uniformity has been changed. Thermocalc software was also used to perform thermodynamic calculations for analyzing the hereditary behavior of W and C elements in the microstructures. If the WC powder and MCrAlY powder shared HVOF spraying equipment, it is recommended to provide MCrAlY powder with a separate powder feeding system to ensure the purity and quality of the coating.
In industrial thermal spray production processes, the workshop and route of powder feeding system needs to be cleaned when changing spraying materials. The powder feeding system include powder feeding tank,powder feeding tray, stirrer, powder feeding pipeline, powder feeding needle. Due to the internal structure of the powder feeding system is complex and the electrostatic adsorption effect, the residual powder in the spray system cannot be completely removed and thus affects the properties of the coating. In this paper, the high-velocity oxyfuel(HVOF) spray technology were adopted to prepare the MCrAlY coatings on the surface of single crystal substrate, the hereditary behavior in the coatings and the interface between coating and substrate of WC impurity particles(WC-10 Co4 Cr) remaining in the powder feeding system was studied. The microstructure and phase composition of WC impurities in spray and heat treatment coatings were analyzed by SEM and EDS. The results showed that WC impurity particles exist in the MCrAlY coatings and would be dissolved into coating and even diffuse into single crystal substrate to form new W carbides during heat treatment and oxidation processes. As a result, the microstructure of coating and single crystal substrate has been affected and the local composition uniformity has been changed. Thermocalc software was also used to perform thermodynamic calculations for analyzing the hereditary behavior of W and C elements in the microstructures. If the WC powder and MCrAlY powder shared HVOF spraying equipment, it is recommended to provide MCrAlY powder with a separate powder feeding system to ensure the purity and quality of the coating.
引文
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[6]田素贵,钱本江,李唐,等.镍基单晶合金中TCP相的析出行为及其对持久性能的影响[J].中国有色金属学报,2010,20(11):2154-2161.
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[9]Sidhu T S,Prakash S,Agrawal R D.State of the art of HVOF coating investigations-a review[J].Marine Technology Society Journal,2005,39(2):53-64.
[10]李长久.超音速火焰喷涂WC-Co涂层结构的研究[J].西安交通大学学报,1994(4):39-45.
[11]Stewart D A,Shipway P H,Mccartney D G.Abrasive wear behaviour of conventional and nanocomposite HVOF-sprayed WC-Co Coatings[J].Wear,1999,225(4):789-798.
[12]Chivavibul P,Watanabe M,Kuroda S,et al,Effects of carbide size and Co content on the microstructure and mechanical properties of HVOF-sprayed WC-Co coatings[J],Surface&Coatings Technology,2007,202(3):509-521.
[13]Brandl W,Toma D,Grabke H J.The characteristics of alumina scales formed on HVOF-sprayed MCrAlYcoatings[J].Oxidation of Metals,2000,53(1-2):125-137.
[14]Yuan K,Peng R L,Li X H,et al.Some aspects of elemental behavior in HVOF MCrAlY coatings in hightemperature oxidation[J].Surface&Coatings Technology,2015,261:86-101.
[15]刘九香,崔向中,高巍,等.两种MCrAlY涂层/DD6合金的循环氧化和互扩散行为[J].航空制造技术.2017(8):37-43.
[16]姚锐,郭洪波,彭徽,等.NiCrAlYSi涂层/DD6单晶高温合金界面再结晶和互扩散行为[J].航空学报,2011,32(4):751-757.
[2]Nicholls J R.Designing oxidation-resistant coatings[J].JOM,2000,52:28-35.
[3]Bose S.High temperature coatings[M].Oxford:Butterworth-Heinemann,2007.
[4]Rae C M F.Reed R C,The precipitation of topologically close-packed phases in rhenium-containing superalloys[J].Acta Materiallia,2001,49(19):4113-4125.
[5]Graverend J B L,Cormier J,Caron P,et al.Numeric simulation ofγ/γ’microstructural evolutions induced by TCP-phase in the MC2 nickel base single crystal superalloy[J].Materials Science&Engineering A,2011,528(6):2620-2634.
[6]田素贵,钱本江,李唐,等.镍基单晶合金中TCP相的析出行为及其对持久性能的影响[J].中国有色金属学报,2010,20(11):2154-2161.
[7]Vardelle A,Moreau C,Akedo J,et al.The 2016 thermal spray roadmap[J].Journal of Thermal Spray Technology,2016,25(8):1376-1440.
[8]Mitchell R.Dorfman,Atin Sharman,challenges and strategies for growth of thermal spray market:the six-pillar plan[J].Journal of Thermal Spray Technology,2013,25:559-563.
[9]Sidhu T S,Prakash S,Agrawal R D.State of the art of HVOF coating investigations-a review[J].Marine Technology Society Journal,2005,39(2):53-64.
[10]李长久.超音速火焰喷涂WC-Co涂层结构的研究[J].西安交通大学学报,1994(4):39-45.
[11]Stewart D A,Shipway P H,Mccartney D G.Abrasive wear behaviour of conventional and nanocomposite HVOF-sprayed WC-Co Coatings[J].Wear,1999,225(4):789-798.
[12]Chivavibul P,Watanabe M,Kuroda S,et al,Effects of carbide size and Co content on the microstructure and mechanical properties of HVOF-sprayed WC-Co coatings[J],Surface&Coatings Technology,2007,202(3):509-521.
[13]Brandl W,Toma D,Grabke H J.The characteristics of alumina scales formed on HVOF-sprayed MCrAlYcoatings[J].Oxidation of Metals,2000,53(1-2):125-137.
[14]Yuan K,Peng R L,Li X H,et al.Some aspects of elemental behavior in HVOF MCrAlY coatings in hightemperature oxidation[J].Surface&Coatings Technology,2015,261:86-101.
[15]刘九香,崔向中,高巍,等.两种MCrAlY涂层/DD6合金的循环氧化和互扩散行为[J].航空制造技术.2017(8):37-43.
[16]姚锐,郭洪波,彭徽,等.NiCrAlYSi涂层/DD6单晶高温合金界面再结晶和互扩散行为[J].航空学报,2011,32(4):751-757.