超音速火焰喷涂制备的WC-WCoB涂层在熔锌中的腐蚀行为及其耐蚀机理
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摘要
目的揭示新型WC-WCoB涂层在锌液中的腐蚀行为及耐蚀机理,从而提高WC基涂层的耐熔锌腐蚀性能。方法以WC、Co和WB粉末为原料,结合离心喷雾干燥和真空热处理,制备得到具有高球形度、结构致密的WC-WCoB热喷涂粉末喂料,并利用超音速火焰喷涂工艺进行涂层的制备。将涂层浸泡于熔融锌液中不同时间,观察其截面组织,以评价涂层的耐熔锌腐蚀性能,并通过X射线衍射仪、热重/差热分析仪、扫描电子显微镜、能谱分析仪对涂层进行结构、性能表征。结果 WCoB相与熔锌间不发生化学反应,制备的WC-WCoB涂层在锌液中浸泡达600 h时,仍未观察到Zn向涂层内的扩散,但在锌液中氧的缓慢作用下,涂层边缘处易产生微裂纹并逐步向内扩展,最终导致涂层材料逐层剥落。WC-WCo B涂层在腐蚀600 h后,完好区域面积占试验涂层总面积的56.3%。结论在传统WC-Co涂层中添加一定量的WB,可使Co相完全转化为WCoB相,与目前广泛使用的WC-η涂层相比,该研究制备的WC-WCoB涂层具有更突出的抗氧化性能,使其在锌液中由于氧化引起的裂纹形成扩展速率显著降低,宏观上表现出更强的耐熔锌腐蚀性能。
The work aims to reveal the corrosion behavior and mechanisms of newly developed WC-WCoB coating against molten zinc so as to improve the corrosion resistance of WC-based coatings. WC-WCoB thermal spray feedstock powder with a high sphericity and high density was prepared by the centrifugal spray drying and subsequent vacuum heat-treatment with WC,Co and WB as raw materials. The coating was then fabricated by the high velocity oxy-fuel(HVOF) spraying technique. The cross-sectional microstructures of the coating after immersion in the liquid zinc for various periods were observed to evaluate the corrosion resistance. The composition, structure and oxidation resistance of the coatings were characterized by X-ray diffraction, thermogravimetric/differential thermal analysis, scanning electron microscopy and energy spectrum analysis. WCoB phase had no chemical reaction with the molten zinc. Besides, there was no evidence showing the diffusion of Zn into the prepared WC-WCoB coating even when the coating had been immersed into the liquid zinc for 600 h. However, the microcracks were easy to initiate at the outer surface of the coating due to the slow oxidation of oxygen dissolved in the liquid zinc. The cracks gradually propagated towards the inner and eventually led to the exfoliation of coating materials layer by layer. After the immersion in molten zinc for 600 h, the area without corrosion accounted for 56.3% of the total area of the WC-WCoB coating. The addition of a certain amount of WB to the conventional WC-Co coating can cause the entire transformation of Co into the WCo B phase. As compared to the currently widely used WC-η coating, the developed WC-WCoB coating in the present work exhibits much higher oxidation resistance. As a result, the formation and growth rates of the oxidation-induced cracks in WC-WCoB coating can be significantly decreased, which then contributes to better corrosion resistance to molten zinc at the macro level.
The work aims to reveal the corrosion behavior and mechanisms of newly developed WC-WCoB coating against molten zinc so as to improve the corrosion resistance of WC-based coatings. WC-WCoB thermal spray feedstock powder with a high sphericity and high density was prepared by the centrifugal spray drying and subsequent vacuum heat-treatment with WC,Co and WB as raw materials. The coating was then fabricated by the high velocity oxy-fuel(HVOF) spraying technique. The cross-sectional microstructures of the coating after immersion in the liquid zinc for various periods were observed to evaluate the corrosion resistance. The composition, structure and oxidation resistance of the coatings were characterized by X-ray diffraction, thermogravimetric/differential thermal analysis, scanning electron microscopy and energy spectrum analysis. WCoB phase had no chemical reaction with the molten zinc. Besides, there was no evidence showing the diffusion of Zn into the prepared WC-WCoB coating even when the coating had been immersed into the liquid zinc for 600 h. However, the microcracks were easy to initiate at the outer surface of the coating due to the slow oxidation of oxygen dissolved in the liquid zinc. The cracks gradually propagated towards the inner and eventually led to the exfoliation of coating materials layer by layer. After the immersion in molten zinc for 600 h, the area without corrosion accounted for 56.3% of the total area of the WC-WCoB coating. The addition of a certain amount of WB to the conventional WC-Co coating can cause the entire transformation of Co into the WCo B phase. As compared to the currently widely used WC-η coating, the developed WC-WCoB coating in the present work exhibits much higher oxidation resistance. As a result, the formation and growth rates of the oxidation-induced cracks in WC-WCoB coating can be significantly decreased, which then contributes to better corrosion resistance to molten zinc at the macro level.
引文
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[15]KIM J,YONG J S,KANG I.First-principles calculations of the phase stability and the elastic and mechanical properties ofη-phases in the WC-Co system[J].Journal of alloys and compounds,2016,656(25):213-217.
[16]杨涛,王海滨,宋晓艳,等.超音速火焰喷涂制备纳米和微米结构WC-η涂层的耐熔锌腐蚀性能[J].无机材料学报,2017,32(8):806-812.YANG Tao,WANG Hai-bin,SONG Xiao-yan,et al.Corrosion resistance of HVOF-sprayed nano-and micon-structured WC-ηcoatings against molten zinc[J].Journal of inorganic materials,2017,32(8):806-812.
[17]WANG H B,YAN X F,LIU X M,et al.Microstructure,mechanical and tribological properties of WC-WCoBcoating[J].Journal of the European Ceramic Society2018,38(15):4874-4881.
[18]YAN X F,WANG H B,SONG X Y,et al.High-temperature oxidation and wear resistance of WC-Co based coatings with WB addition[J].Journal of the European Ceramic Society,2017,36(3):4547-4561.
[19]殷小龙,尹海清,DILFARAZ K,等.反应硼化烧结WCo B基金属陶瓷的组织与性能[J].材料导报,2015,29(2):57-59.YIN Xiao-long,YIN Hai-qing,DILFARAZ K,et al.Structure and Mechanical properties of WCoB-based cermets through reaction boronizing sintering[J].Materials review,2015,29(2):57-59.
[20]LIU Y R.Comparison of HVOF and plasma-spayed alumina-titanium coating[J].Surface and coating technology,2003,167:68-76.
[21]MI P,WANG T,YE F.Influences of the compositions and mechanical properties of HVOF sprayed bimodal WC-Co coating on its high temperature wear performance[J].International journal of refractory metals&hard materials,2017,69:158-163.
[22]李德元,张广伟,张楠楠.热喷涂WC-12Co涂层在锌液中腐蚀失效过程分析[J].焊接学报,2017,38(12):23-28.LI De-yuan,ZHANG Guang-wei,ZHANG Nan-nan.Failure process of thermal sprayed WC-12Co coating in liquid zinc corrosion[J].Transactions of the China welding institution,2017,38(12):23-28.
[2]SHE Jun,REN Xian-jing,YU Yue-guang,et al.Advance in research on surface corrosion-consistant of sink roll in galvanization[J].Materials review,2006,20:429-435.
[3]WANG Sheng-min,ZHAO Xiao-jun,DANG Jian-wei,et al.Research status of the process mechanism of batch hot-dip galvanizing[J].Surface technology,2016,45(5):19-25.
[4]TOWNSEND H E.Continuous hot dip coatings[J].Surface engineering,1994,5:339-348.
[5]MATTHEWS S,JAMES B.Review of thermal spray coating applications in the steel industry:Part 2-zinc pot hardware in the continuous galvanizing line[J].Journal of thermal spray technology,2010,19(6):1277-1286.
[6]FAN Zi-shuan.The mechanism and countermeasure of molten zinc corrosion of sink roll in hot dip galvanizing bath[J].Thermal spray technology,2010,2(1):1-7.
[7]LI De-yuan,XIE Tian-nan,YIN Yan-dong,et al.Zinc corrosion resistant behavior of HVAF sprayed Co based WC coating[J].Journal of Shenyang University of Technology,2013,21(4):385-389.
[8]REN J P,LIU M,DENG C M,et al.Corrosion resistance of WC coatings sprayed by AC-HVAF on aluminum alloy in neutral salt spray[J].Materials for mechanical engineering,2009,33(3):39-42.
[9]VARIS T,SUHONEN T,GHABCHI A,et al.Formation mechanisms,structure,and properties of HVOF-sprayed WC-CoCr coatings:An approach toward process maps[J].Journal of thermal spray technology,2014,23(6):1009-1018.
[10]吕和平.新型三元硼化物基陶瓷涂层的制备及其性能研究[D].上海:上海交通大学,2010.LYU He-ping.Preparation and study of a few ternary borides based ceramic coating[D].Shanghai:Shanghai Jiaotong University,2010.
[11]MARIN E,LANZUTTI A,GUZMAN L,et al.Corrosion protection of AISI 316 stainless steel by ALD alumina/titania nanometric coatings[J].Journal of coatings technology&research,2011,8(5):655-659.
[12]TOMITA T,TATATANI Y,KOBAYASHI Y,et al.Durability of WC/Co sprayed coatings in molten pure zinc[J].Transactions of the iron&steel institute of Japan,200733(9):608-615.
[13]TANI K,TOMITA T,KOBAYASHI Y,et al.Durability of WC/Co coatings in Al-added zinc bath[J].ISIJ international,1994,34(10):822-828.
[14]WANG H B,HOU C,LIU X M,et al.Phase evolution in synthesis of nanocrystalline WC-ηcomposite powder by solid-state in situ reactions[J].International journal of refractory metals&hard materials,2018,71:21-27.
[15]KIM J,YONG J S,KANG I.First-principles calculations of the phase stability and the elastic and mechanical properties ofη-phases in the WC-Co system[J].Journal of alloys and compounds,2016,656(25):213-217.
[16]杨涛,王海滨,宋晓艳,等.超音速火焰喷涂制备纳米和微米结构WC-η涂层的耐熔锌腐蚀性能[J].无机材料学报,2017,32(8):806-812.YANG Tao,WANG Hai-bin,SONG Xiao-yan,et al.Corrosion resistance of HVOF-sprayed nano-and micon-structured WC-ηcoatings against molten zinc[J].Journal of inorganic materials,2017,32(8):806-812.
[17]WANG H B,YAN X F,LIU X M,et al.Microstructure,mechanical and tribological properties of WC-WCoBcoating[J].Journal of the European Ceramic Society2018,38(15):4874-4881.
[18]YAN X F,WANG H B,SONG X Y,et al.High-temperature oxidation and wear resistance of WC-Co based coatings with WB addition[J].Journal of the European Ceramic Society,2017,36(3):4547-4561.
[19]殷小龙,尹海清,DILFARAZ K,等.反应硼化烧结WCo B基金属陶瓷的组织与性能[J].材料导报,2015,29(2):57-59.YIN Xiao-long,YIN Hai-qing,DILFARAZ K,et al.Structure and Mechanical properties of WCoB-based cermets through reaction boronizing sintering[J].Materials review,2015,29(2):57-59.
[20]LIU Y R.Comparison of HVOF and plasma-spayed alumina-titanium coating[J].Surface and coating technology,2003,167:68-76.
[21]MI P,WANG T,YE F.Influences of the compositions and mechanical properties of HVOF sprayed bimodal WC-Co coating on its high temperature wear performance[J].International journal of refractory metals&hard materials,2017,69:158-163.
[22]李德元,张广伟,张楠楠.热喷涂WC-12Co涂层在锌液中腐蚀失效过程分析[J].焊接学报,2017,38(12):23-28.LI De-yuan,ZHANG Guang-wei,ZHANG Nan-nan.Failure process of thermal sprayed WC-12Co coating in liquid zinc corrosion[J].Transactions of the China welding institution,2017,38(12):23-28.