Characteristics and corrosion performance of 80Ni-20Cr coating deposited by on-site thermal spraying

New controlled atmosphere on-site spraying systems were developed to deposit a high-quality coating with superior resistance to wet corrosion. Characteristics and corrosion resistance of coatings deposited by arc and flame spraying of wire in argon gas were compared with those of coatings deposited by conventional and low-pressure plasma techniques. It was found that the coating deposited by the arc spraying of wire in argon gas is free of oxides and possesses excellent corrosion resistance in chloride and acid solutions. The coating suffers slight pitting and crevice corrosion associated with the isolated pores and electric potential paths. Corrosion resistance was improved by using a modified spraying system.     

STUDY OF HOT CORROSION RESISTANCE MECHANISMS OF ARC SPRAYING COATINGS

１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｏｒｒｏｓｉｏｎｐｒｏｔｅｃｔｉｏｎｏｆｉｎｄｕｓｔｒｙｂｏｉｌｅｒｔｕｂｅｓｉｓａｎｉｍｐｏｒｔａｎｔｅｃｏｎｏｍｉｃｐｒｏｂｌｅｍ．Ｔｈｅｈｏｔｃｏｒｒｏｓｉｏｎｏｆｂｏｉｌｅｒｔｕｂｅｓｔｈｒｅａｔｅｎｓｓｅｒｉｏｕｓｌｙｔｈｅｓｅｃｕｒｉｔｙｏｐｅｒａｔｉｏｎｏｆｐｏｗｅｒｓｔａｔｉｏｎ．Ｃｕｒｒｅｎｔｌｙ,ｓｏｍｅｃｏｕｎｔｒｉｅｓｄｅａｌｗｉｔｈｔｈｉｓｐｒｏｂｌｅｍｂｙｔｈｅｒｍａｌｓｐｒａｙｔｅｃｈｎｏｌｏｇｙａｎｄａｃｈｉｅｖｅｇｏｏｄｒｅｓｕ…     

电弧喷涂锌涂层的酸雨腐蚀性能

热镀锌涂层因具有优越的耐腐蚀性、涂装性能等被广泛应用于工业生产众多领域,成为金属材料在户外工作环境下防腐蚀的有效措施之一。为研究热喷涂锌涂层在酸雨中的腐蚀行为,采用电弧喷涂技术在Q235碳素结构钢表面喷涂锌涂层,模拟酸雨腐蚀环境,在腐蚀液pH值改变的情况下,采用SEM,XRD,硬度测试及失重分析等手段,分析不同pH值溶液腐蚀后涂层的表面形貌和腐蚀产物,及试样的硬度变化和腐蚀速率情况。结果表明,锌涂层的表面腐蚀会随着模拟酸雨溶液pH值的降低而加重,其表面腐蚀产物逐渐增多,腐蚀产物的形貌由小块状逐渐变成羽针状和岛状,主要成分为Zn(OH)2,ZnSO4和Zn4SO4(OH)6·3H2O;涂层表面硬度最高为23.4 HV、最小腐蚀速率为0.21×10-4g/(m2·h),但当模拟酸雨溶液pH值由7降至2.8时,涂层表面硬度降低约12%,腐蚀速率约增大至最小值的26倍;模拟酸雨溶液pH值在5～2.8时,溶液对锌涂层的腐蚀比较严重。     

三种电弧喷锌防护涂层在3.5% NaCl溶液中的耐蚀性

采用电弧喷涂技术在Q235钢基体上制备出纯锌、Zn-Al合金和Zn-Al伪合金涂层。通过浸泡试验和电化学测试考察涂层在3.5%NaCl溶液中的腐蚀行为,并结合扫描电镜(SEM)和X射线衍射仪(XRD)分析了涂层腐蚀后的表面形貌及腐蚀产物的相结构。结果表明,在3.5%NaCl溶液中三种涂层的耐腐蚀性按Zn-Al伪合金涂层、Zn-Al合金涂层、Zn涂层的顺序依次降低。     

Cr元素含量对镍基合金涂层抗热腐蚀行为的影响

采用高速电弧喷涂技术在20G钢基体表面制备三种铬含量不同的镍基合金涂层.光学显微镜、X射线衍射、扫描电镜和能谱分析等技术对涂层微观组织结构、相组成及成分进行分析.选用摩尔比为7:3的Na₂SO₄+K₂SO₄水溶液涂敷刷在涂层表面,分析涂层在650℃下的抗热腐蚀性能.结果表明,涂层的腐蚀动力学曲线基本符合抛物线规律;四种涂层表面均形成了致密连续的NiO和Cr₂O₃保护膜.随着铬含量升高,涂层表面氧化膜中Cr₂O₃含量升高,NiO逐渐减少,涂层抗热腐蚀性能明显提高.Ni-30Cr,Ni-45Cr,Ni-50Cr涂层抗热腐蚀性能分别为20G钢基体的10,15和20倍;Ni-50Cr涂层抗腐蚀性能是美国Tafa 45CT材料的1.4倍.     

CO2气氛和喷涂距离对电弧喷涂铁基非晶涂层组织及耐蚀性能的影响

为提高电弧喷涂铁基非晶涂层的非晶含量及耐蚀性,以CO₂为载流气体代替空气进行电弧喷涂试验,并研究喷涂距离对涂层组织与耐蚀性的影响。结果表明,喷涂层的厚度约为200 μm,涂层均主要由结晶相与非晶相构成。相比于空气介质,CO₂抑制了晶化,从而提高了涂层中的非晶含量。同时,喷涂距离对涂层的组织及耐蚀性能有较大影响。随着喷涂距离的增加,涂层中的非晶含量减少。当喷涂距离为100 mm时,涂层具有最高的开路电位-0.498 V(vs SCE)及最小的自腐蚀电流密度4.281 μA/cm²,耐蚀性能最好;当喷涂距离为150 mm时,涂层的耐蚀性最差。提高非晶含量和组织的均匀性可增强该涂层的耐蚀性能。     

电弧离子镀NiCrAlY涂层900℃的热腐蚀行为

采用电弧离子镀技术在镍基单晶合金上沉积Ni28Cr11Al0.5Y涂层,并研究了镍基单晶合金及有Ni28Cr11Al0.5Y涂层镍基单晶合金在900℃的75%Na2SO4+25%K2SO4熔盐中的热腐蚀行为。结果表明,镍基单晶合金遭受了破坏性的热腐蚀,出现了严重的内硫化和内氧化;而由于Ni28Cr11Al0.5Y涂层在熔盐中生成连续的Al2O3氧化膜,阻止了熔盐对单晶合金的腐蚀,有涂层镍基单晶合金表现出优良的抗热腐蚀性能。     

铝-镁金属间化合物涂层的制备与分析

采用铝/镁异质双丝电弧喷涂+热处理复合工艺在铸造铝合金表面制备了铝-镁金属间化合物防护涂层.通过金相显微镜、电子探针及XRD衍射仪对涂层的组织和相组成进行研究,分析了热处理工艺对涂层组织的影响.采用质量分数5%的NaCl溶液进行浸泡试验和电化学试验,对比分析了热处理前后涂层的耐腐蚀性能.结果表明,热处理可显著改变涂层内...     

Fe/Cr涂层抗热腐蚀性能研究

设计制造出Fe/Cr粉芯丝材,利用电弧喷涂技术制备出耐高温腐蚀的工作涂层。运用光学显微镜、扫描电子显微镜(SEM)、X射线衍射仪(XRD)等研究了电弧喷涂Fe/Cr合金涂层的微观结构、腐蚀动力学和高温下的腐蚀性能。结果表明,该涂层组织致密,涂层中形成Cr2O3或尖晶石型氧化物是其具有优异的抗高温腐蚀性能的主要原因,涂层抗高温腐蚀性能较好。     

Failure mechanism of MCrAlY coating at the coating‐substrate interface under type I hot corrosion

MCrAlY coatings are widely used to provide protection of hot component in modern gas turbine engines against high‐temperature oxidation and hot corrosion. Coating‐substrate interface, where the substrate is only partially covered by the ?coatings, is vulnerable to the hot corrosion attack. The accelerated degradation at the coating‐substrate interface can cause fast spallation of the coating, leading to the early failure of the gas turbine components. In this paper, MCrAlY powder was deposited on IN792 disks by high‐velocity oxygen‐fuel spraying. The hot corrosion behavior of the coated sample was investigated using (0.8Na, 0.2K)₂SO ₄ salt deposition at 900°C in lab air. Results showed a minor attack in the coating center, however, an accelerated corrosion attack at the coating‐substrate interface. The fast growth of corrosion products from substrate caused large local volume expansions at the coating‐substrate interface, resulting in an early coating spallation.     

Structure and Properties Characterization of Ceramic Coatings Produced on Steel Using a Combined Technique

STEEL is the most widely used material in engineering,but unfortunately,steel exhibits poor wear resistanceand obvious contact corrosion.For decades,researchersprepared coatings on steel to improve its properties;ceramic is one of these coatings.To obtain ceramiccoatings on steel,many researchers use techniques suchas plasma spraying,laser cladding,etc.,but some ofthem are too expensive,some of them have a deep heataffected zone in the substrate,and some of them cannot bond well with the subs…     

Ti60合金表面电弧离子镀Ti-Al-Cr(Si,Y)防护涂层的热腐蚀行为

采用电弧离子镀技术在Ti60合金表面制备了Ti-48%Al-12%Cr(0.2%Si,0.1%Y,原子分数)防护涂层.利用XRD,SEM和EDS研究了Ti60合金及Ti-Al-Cr(Si,Y)涂层在Na_2SO_4和75%Na_2SO_4+25%K_2SO_4(质量分数)中800及850℃下的热腐蚀行为.结果表明,Ti60合金基体在800和850℃的硫酸盐中发生了严重的腐蚀,腐蚀产物发生了明显剥落.涂层样品在800和850℃的硫酸盐腐蚀介质中,表面形成了保护性的氧化膜,可以有效地保护Ti60合金免受腐蚀破坏.Ti60合金及涂层样品在75%Na_2SO_4+25%K_2SO_4混合硫酸盐中的腐蚀比在纯K_2SO_4中剧烈.Si和Y元素的加入使得Ti-Al-Cr-Si和Ti-Al-Cr-Si-Y涂层在硫酸盐中抗热腐蚀性能优于Ti-Al-Cr涂层.     

Q235上电弧喷涂Zn55Al涂层在3.5wt%溶液中的腐蚀行为研究

本文使用电弧喷涂通过包套挤压+拉拔的方法制备的Zn55Al伪合金丝材成功的在Q235钢上喷涂出了Zn55Al涂层。通过扫描电镜和微区XRD研究了Zn55Al 伪合金丝材的显微结构。通过浸泡腐蚀实验和电化学方法研究了Zn55Al涂层、Zn15Al涂层和 Al涂层的腐蚀行为,并对比了三种涂层之间的差异。结果表明Zn55Al伪合金丝材由纯锌和纯铝组成,在整个成型过程中没有产生合金化。Zn55Al涂层由层片状的富锌相和富铝相组成。经过20天的浸泡实验,Zn55Al涂层形成了一层致密的钝化膜,比其他两种涂层有更好的耐腐蚀性。Zn55Al涂层的自腐蚀电位大约是-1.25v,高于Zn15Al涂层低于纯Al涂层和Q235基体.电偶腐蚀实验表明,Zn55Al涂层比Zn15Al涂层具有更好的点虎穴保护作用。这些结果说明Zn55Al涂层具有更好的耐腐蚀性和可以给Q235基体提供更强的电化学保护.本文也讨论了Zn55Al涂层的的腐蚀机理。     

单相和双相不锈钢纳米涂层的电化学腐蚀行为

用磁控溅射技术在玻璃基体上制备由两种相组成(单相和双相)的不锈钢纳米涂层,利用动电位极化､交流阻抗技术及扫描电子显微镜研究两种不锈钢纳米涂层在0.25 mol/L Na2SO4 + 0.05 mol/L H2SO4 和 0.5 mol/L NaCl + 0.05 mol/L H2SO4溶液中的电化学腐蚀行为,观察相组成对纳米不锈钢涂层耐蚀性能的影响｡结果表明,与不锈钢单相涂层相比,不锈钢双相纳米涂层具有较差的抗局部腐蚀能力,其钝化膜的载流子密度远远大于不锈钢单相钝化膜的载流子密度,使得钝化膜的离子传输能力大大增强,从而降低了钝化膜的稳定性｡     

Corrosion Behaviors of Nitride Coatings on Titanium Alloy in NaCl-Induced Hot Corrosion

TiN and TiAlN coatings were deposited by arc ion plating on titanium alloys to study their hot corrosion resistance when they were exposed to NaCl at 600 ℃.The microstructure and corrosion behaviors of nitride coatings were studied using scanning electron microscope,X-ray diffraction,electro-probe microanalyzer and X-ray photoelectron spectroscopy.The results showed that nitride coatings with the different compositions and the ones with the same composition but different thicknesses presented different hot corrosion resistance.TiN and thin TiAlN coatings showed poor corrosion resistance.Serious internal oxidation attacked the alloy substrate.Their corrosion products were mainly consisted of non-protective TiO2 and sodium salt.By contrast,the thick TiAlN coating presented outstanding corrosion resistance.Besides sodium salt,the corrosion products were composed of protective Al2O3.The increasing thickness of TiAlN significantly enhanced the hot corrosion resistance.The corrosion mechanisms of alloy,TiN and TiAlN coatings were discussed in detail.     

超音速等离子喷涂制备金属陶瓷涂层的抗冲蚀性能

通过高效能超音速等离子喷涂(SAPS)制备WC-Co及WC-Ni Cr金属陶瓷涂层,对比研究了2种涂层的抗冲蚀性能及在热腐蚀条件下的结构和性能演变。结果表明:2种涂层在喷涂过程中均会发生一定程度的脱碳,表现为W_2C相的形成;同时在WC-Co涂层中有少量的Co_3W_3C和Co_6W_6C相生成,且该涂层在热腐蚀后表层的WC相出现了分解与氧化,形成了W_3C、W_6C_(2.54)等脱碳相与CoWO_4、WO_3等氧化物相。在普通冲蚀条件下,WC-Co涂层的抗冲蚀性能更为优异,但热腐蚀会极大降低WC-Co涂层的抗冲蚀性能;与之相反,WC-NiCr涂层中的NiCr相在热腐蚀环境下生成的Cr_2O_3可以有效阻挡涂层内部与外部之间的物质扩散,从而降低了热腐蚀对涂层结构的破坏,在热腐蚀条件下表现出了优良的抗冲蚀性能。     

TiAl合金表面激光重熔MCrAlY涂层热腐蚀性能

采用等离子喷涂技术在TiAl合金表面制备了MCrAlY涂层,并用激光重熔工艺对涂层进行处理,研究了TiAl合金、等离子喷涂MCrAlY涂层及激光重熔MCrAlY涂层850℃下75%Na₂SO₄+25%NaCl(质量分数)混合盐浸泡热腐蚀性能,分析了不同试样的热腐蚀破坏机理,并讨论了激光重熔处理对涂层热腐蚀性能的影响.结果表明,等离子喷涂MCrAlY涂层能显著提高TiAl合金的耐热腐蚀性能,经过激光重熔后可进一步提高其耐热腐蚀性能.MCrAlY涂层在高温熔盐中的热腐蚀发生的是表面氧化反应和内部硫化反应,主要生成Al₂O₃,Cr₂O₃,NiO,NiCr₂O₄,Ni₃S₂及CrS等腐蚀产物.     

电弧喷涂防腐蚀涂层研究

介绍了电孤喷涂稀土铝、铝合金涂层抗腐蚀性能试验,高速电弧喷涂锌、铝涂层的防腐蚀性能试验结果.指出喷涂材料和喷涂设备的发展情况,提高了涂层的防腐蚀性能,使电弧喷涂能够在防腐蚀领域得到更广泛的应用.     

电弧喷涂Al-Zn-Si-RE合金涂层与Al-Zn伪合金涂层的耐蚀性能对比

为研究Al-Zn-Si-RE合金涂层和相同Al含量的Al-Zn伪合金涂层耐蚀性能的不同,采用电弧喷涂技术在Q235钢表面制备了此两种合金涂层。通过盐水全浸实验和电化学测试技术对比研究了两种涂层的耐腐蚀性能,并将两种涂层的极化曲线与纯Zn、纯Al、Zn-15Al合金涂层进行了对比分析。使用扫描电镜、金相显微镜和X-射线衍射仪等手段测试分析了两种合金涂层腐蚀前后的微观组织形貌和相组成。结果表明,Al-Zn-Si-RE合金涂层的自腐蚀电位和自腐蚀电流密度分别为-0.995V和3.319×10-6 A/cm2,腐蚀电位更正,腐蚀电流密度更低,耐蚀性更好,原因可能是致密的腐蚀产物膜抑制了腐蚀作用;Al-Zn-Si-RE合金涂层与伪合金涂层微观组织成分和相结构的不同引起腐蚀行为的差异,且Al-Zn-Si-RE合金涂层表现出更好的耐盐水腐蚀性能;稀土元素的存在有利于提高Al-Zn-Si-RE合金涂层的耐蚀性。     

Degradation Behavior of Nanostructured Coatings Deposited by High-Velocity Arc Spraying Process in an Actual Environment of a Coal-Fired Boiler

FeCr-based nanostructured coatings were deposited on a 301S stainless steel substrate by the high-velocity arc spraying process in the current work. The oxidation behavior of the coatings exposed to elevated temperatures (700°C and 900°C) under laboratory conditions as well as in an actual industrial environment of a coal-fired boiler (at 700 ± 10°C) was investigated. X-ray diffraction, scanning electron microscopy/energy-dispersive analysis, and transmission electron microscopy techniques were used to characterize the coating as well as to analyze the corrosion products for elucidating the corrosion mechanisms. The microhardness of the coating was found to be 520–1100 HV. The (FeCr)-based nanostructured coating showed good adherence to the 310S substrate and excellent oxidation resistance during the exposures with no tendency for spallation of its oxide scales in both environments. The nanosized grain morphology of the coating facilitated the formation of protective scales, which is continuous, adherent, and nonporous due to the higher diffusivity of alloying elements in the coatings. It precludes high-temperature oxidation by acting as a diffusion barrier between the environment and the coating.