Erosion resistance of arc-sprayed coatings to iron ore at 25 and 315 °C

Iron ore pellets are sintered and reduced in large continuous industrial oil-fired furnaces. From the furnace, powerful fans extract large volumes of hot gas. Being exposed to gas-borne iron ore particles and temperatures ranging between 125 and 328 °C, fan components are rapidly eroded. Extensive part repair or replacement is required for maintaining a profitable operation. The arc spraying technique has been suggested for repair provided it could produce erosion-resistant coatings. Conventional and cored wires (1.6 mm diameter) were arc sprayed using various spray parameters to produce 250 to 300 μm thick coatings. Arc-sprayed coatings and reference specimens were erosion tested at 25 and 315 °C and impact angles of 25 and 90° in a laboratory gas-blast erosion rig. This device was designed to impact materials with coarse (32 to 300 μm) iron ore particles at a speed of 100 m/s. The coating volume loss due to erosion was measured with a laser profilometer built by National Research Council Canada several years ago. Few arc-sprayed coatings exhibited erosion resistance comparable with structural steel at low impact angles. Erosion of arc-sprayed coatings and reference specimens dramatically increases at 315 °C for both 25° and 90° impact angles. Erosion-enhanced oxidation was found to be responsible for the increase in volume loss above room temperature. Though arc spraying can be appropriate for on-site repair, the development of more erosion-resistant coatings is required for intermediate temperatures.     

Development of cored wires for improving the abrasion wear resistance of austenitic stainless steel

Arc-sprayed coatings are an attractive means to protect components from abrasive wear provided they contain enough hard phases. Because of their hardness and toughness, 316L-TiB₂ cermets were selected as the basis for developing wear-resistant coatings. Cored wires composed of type 304 stainless steel sheaths filled with 10 to 65 wt% TiB₂,1 to 15 wt% additives, and the balance with 316L stainless steel were fabricated and arc-sprayed with air. The arc-sprayed stainless steel-TiB₂ coatings were abrasion tested and the volume loss measured with an optical profiloineter. The volume loss decreased as the proportion of TiB₂ increased. However, large differences in volume loss between coatings that contain about the same volumetric proportion of hard phases cannot be explained by a linear relationship. An inverse rule of mixing was proposed and found useful in determining the influence of different additives. Tin, added in the core as a fugitive liquid transfer agent, was the most powerful additive for improving the wear resistance of stainless steel-base coatings. These advanced arc-sprayed stainless steel-TiB2 coatings exhibit greater wear resistance than those obtained by arc spraying commercial solid and cored wires.     

高速电弧喷涂Fe3Al/WC复合涂层高温冲蚀行为研究

采用自行研制的新型热喷涂Fe3Al/WC复合合金粉芯丝材,成功地用高速电弧喷技术制备出了Fe3Al金属化合物基金属陶瓷复合涂层。对涂层成分、显微组织、涂层相结构和组成进行了分析,结果表明,涂层由以Fe-26Al为主的Fe3Al基体相与约20%的WC、W2C和 a-Al2O3相组成。对比研究了Fe3Al/WC涂层和电站锅炉钢20 g从室温至650 ℃氧化环境条件下不同攻角的高温冲蚀磨损性能,结果表明Fe3Al/WC涂层的高温冲蚀磨损抗力高于20 g钢,650 ℃和30°攻角下的稳态相对冲蚀磨损抗力为20 g钢的3.14倍。温度对Fe3Al/WC涂层的冲蚀行为有较大影响：温度 < 450℃,涂层的冲蚀率变化不大,表现出塑性材料的冲蚀行为;温度 >450 ℃,涂层冲蚀率变化较大,呈现典型的脆性材料冲蚀磨损行为。并对其高温冲蚀磨损机理进行了分析。     

Abrasion wear resistance of arc-sprayed stainless steel and composite stainless steel coatings

The abrasion wear resistance of stainless steel and composite stainless steel/titanium boride coatings arc sprayed with air and argon was evaluated. Stainless steel coatings arc sprayed with air were found to be slightly more resistant than bulk stainless steel, whereas those sprayed with argon were slightly less resistant. The wear resistance of composite stainless steel/titanium diboride coatings was from two to four times greater than that of bulk stainless steel, depending on the cored wire constitution and the type of gas used for spraying. Microstructural analysis, microhardness measurements, and optical profilometry were used to characterize the coatings and wear damage. By considering both the wire constitution and the spraying conditions, it was possible to fabricate composite stainless steel coatings that showed a 400 % increase in wear resistance over bulk stainless steel.     

温度对高速电弧喷涂Fe-Al/Cr3C2涂层的影响

采用Fe—Al／Cr3C2粉芯丝材和高速电弧喷涂技术(HVAS)原位合成了复合涂层，对不同温度下涂层的组织和性能进行了研究。结果表明，随着温度的升高，涂层的耐冲蚀性能提高，涂层的耐蚀性能变化不大，涂层的结合强度提高，并且涂层表面氧化物膜增多，涂层组织颗粒变小，涂层结合处出现冶金结合。     

热喷涂FeCrAl/WC涂层的组织和高温冲蚀行为

采用粉芯丝材和高速电弧喷涂技术制备高温氧化环境下抗冲蚀磨损FeCrAl/WC涂层。用扫描电子显微镜、能谱仪和X射线衍射仪对FeCrAl/WC涂层的组织、成分和涂层表面冲蚀磨损形貌进行了分析。用自制的高温冲蚀磨损试验机对FeCrAl/WC涂层在不同温度、攻角下的冲蚀磨损性能进行了测试。结果表明 ,高速电弧喷涂FeCrAl/WC涂层具有颗粒增强复合材料的层状组织特征。 4 5 0℃以下 ,FeCrAl/WC涂层均呈现韧性冲蚀行为 ;90°攻角时不同温度以及 6 5 0℃时不同攻角对FeCrAl/WC涂层的冲蚀行为影响不大。温度高于 35 0℃ ,FeCrAl/WC涂层具有良好的全攻角冲蚀磨损抗力 ,6 5 0℃棱角状石英磨粒冲蚀条件下 ,FeCrAl/WC涂层的冲蚀磨损抗力为 2 0g钢的 1 .94～ 2 .0 3倍。探讨了FeCrAl/WC涂层高温冲蚀磨损机理     

High-Temperature Erosion Resistance of FeBSiNb Amorphous Coatings Deposited by Arc Spraying for Boiler Applications

Erosive high-temperature wear in boilers is one of the main causes of downtime and one of the principal engineering problems in these installations. This article discusses the use of FeBSiNb amorphous coatings synthesized by arc spraying to improve elevated-temperature erosion resistance for boiler applications. The influence of test temperature, velocity, and impact angle on material wastage was revealed using air solid particle erosion rig. The experimental results showed that moderate degradation of the coating was predominant at lower impact velocity and impact angles, while severe damage arose for higher velocities and impact angles. The erosion behavior of the coating was sensitive to test temperature. The erosion rates of the coating decreased as a function of environment temperature. The relationship between microstructure and erosion resistance of the coating was also analyzed in details. The FeBSiNb coating had excellent elevated-temperature erosion resistance at temperatures at least up to 600 °C during service.     

High Power Diode Laser-Treated HP-HVOF and Twin Wire Arc-Sprayed Coatings for Fossil Fuel Power Plants

This article deals with high power diode laser (HPDL) surface modification of twin wire arc-sprayed (TWAS) and high pressure high velocity oxy-fuel (HP-HVOF) coatings to combat solid particle erosion occurring in fossil fuel power plants. To overcome solid particle impact wear above 673 K, Cr₃C₂-NiCr-, Cr₃C₂-CoNiCrAlY-, and WC-CrC-Ni-based HVOF coatings are used. WC-CoCr-based HVOF coatings are generally used below 673 K. Twin wire arc (TWA) spraying of Tafa 140 MXC and SHS 7170 cored wires is used for a wide range of applications for a temperature up to 1073 K. Laser surface modification of high chromium stainless steels for steam valve components and LPST blades is carried out regularly. TWA spraying using SHS 7170 cored wire, HP-HVOF coating using WC-CoCr powder, Ti6Al4V alloy, and high chromium stainless steels (X20Cr13, AISI 410, X10CrNiMoV1222, 13Cr4Ni, 17Cr4Ni) were selected in the present study. Using robotically controlled parameters, HPDL surface treatments of TWAS-coated high strength X10CrNiMoV1222 stainless steel and HP-HVOF-coated AISI 410 stainless steel samples were carried out and these were compared with HPDL-treated high chromium stainless steels and titanium alloy for high energy particle impact wear (HEPIW) resistance. The HPDL surface treatment of the coatings has improved the HEPIW resistance manifold. The improvement in HPDL-treated stainless steels and titanium alloys is marginal and it is not comparable with that of HPDL-treated coatings. These coatings were also compared with “as-sprayed” coatings for fracture toughness, microhardness, microstructure, and phase analyses. The HEPIW resistance has a strong relationship with the product of fracture toughness and microhardness of the HPDL-treated HP-HVOF and TWAS SHS 7170 coatings. This development opens up a possibility of using HPDL surface treatments in specialized areas where the problem of HEPIW is very severe. The HEPIW resistance of HPDL-treated high chromium stainless steels and titanium alloys, HPDL-treated TWAS SHS 7170 and HP-HVOF coatings, and their micrographs and X-ray diffraction analysis is reported in this article.     

A Study on Cavitation Erosion and Corrosion Behavior of Al-, Zn-, Cu-, and Fe-Based Coatings Prepared by Arc Spraying

Investigation to find a suitable coating material for a rudder application has been carried out in this study. Ten different coatings were prepared by arc spraying with Al-, Zn-, Cu-, and Fe-based wire feedstock. Both the cavitation erosion and marine corrosion behavior of the arc-sprayed coatings were evaluated, and compared with the conventional anti-corrosion paint. In terms of marine corrosion resistance, aluminum coating was the best among the tested coating systems while stainless steel coating showed the highest resistance against cavitation erosion. In addition, the effects of both the Si composition in Al-based coatings and the Ni composition in Cu- and Fe- based coatings were discussed in this study.     

Arc-Sprayed Iron-Based Coatings for Erosion-Corrosion Protection of Boiler Tubes at Elevated Temperatures

Wire arc spraying is an economically attractive thermal spray process that is especially interesting for the protection of large-scale parts or constructions. This study presents the results of the development and investigation of a number of cored wires based on the Fe-Cr-Al system with minor addition of alloying elements (B, Mn, Ni, Si, Ti, Mg, etc.). The microstructure of the coatings, their electrochemical behavior, and isothermal oxidation performance over a temperature range of 20-700 °C were investigated. Erosion resistance at elevated temperatures was determined with a laboratory test unit under test conditions that have simulated the work conditions in fossil-fuel-fired boilers. It was established that the oxidation resistance and the gas-abrasive wear resistance of arc-sprayed coatings depend mostly on the coating microstructure and homogeneity of element distribution rather than on the general alloying level and microhardness of the coating. A new parameter for coating characterization, namely, the coefficient of chemical microheterogeneity, K _CMH, is introduced to quantify this influence. Formation of the coating microstructure at elevated temperatures and its influence on the protection ability of the coating are discussed.     

装备修复用铜合金涂层制备方法及应用研究

目的为解决某型舰水泵叶轮轮毂等装备关键部件修复的难点问题,对电弧喷涂制备的铜合金涂层进行了重点研究。方法通过光学显微镜、扫描电子显微镜、显微硬度计、拉伸试验机、磨损试验机等对所制备的涂层的显微形貌、显微硬度、结合强度、抗冲蚀性能等进行了评定。结果采用电弧喷涂技术制备的铜合金涂层组织致密,涂层与基体之间的结合强度平均值为18.58 MPa,显微硬度平均值为187.5HV0.3,高于基体硬度,孔隙率平均值为4.1%,冲蚀角为30°和90°时,铜合金涂层的磨损质量分别为0.024 g和0.020 g,显示出优异的耐磨抗冲蚀性能。结论采用电弧喷涂技术在水泵叶轮轮毂表面制备了铜合金涂层,不仅恢复了原设计尺寸,而且大幅提升了水泵叶轮表面的耐磨抗冲蚀性能,同时基体不产生变形,不需要进行动平衡试验,节能节材,预计使用寿命可提高3倍以上。该技术可为大、新型装备其他关键铜质部件维修保障提供新思路和新方法。     

碳化硼对电弧喷涂涂层性能的影响

将碳化硼(B4C)陶瓷粉末和其它合金元素与304L不锈钢带轧制成粉芯丝材,采用电弧喷涂技术制备金属陶瓷复合涂层.研究了B4C在电弧喷涂中的应用.利用XRD,SEM对涂层的形貌、相组成和磨损表面进行了分析.利用自行设计的高温磨粒磨损装置和高温冲蚀设备分别评价了B4C对涂层耐高温磨粒磨损性能和耐高温冲蚀性能的影响.结果表明,粉芯丝材喷涂工艺良好,B4C陶瓷与粉芯中其它组分反应,可以形成含Fe3B,CrB,FexN i23-xB6,Fe23(C,B)6,(Cr,Fe)7C3和Fe3C等硬质相的复合涂层,大幅度提高了涂层的硬度和耐磨耐冲蚀性能.     

高速电弧喷涂FeMnCr/Cr3C2涂层抗高温冲蚀磨损性能

针对超临界锅炉管道的严重冲蚀磨损问题,采用高速电弧喷涂技术在20钢表面制取耐磨涂层,并研究其高温冲蚀磨损特性。采用场发射扫描电子显微镜和X射线能谱分析等方法探讨涂层的冲蚀磨损规律。结果表明,FeMnCr/Cr3C2涂层最大冲蚀率出现在冲击角60°附近,表现出半塑性冲蚀磨损特征;其耐高温冲蚀性与FeCrNi/Cr3C2涂层相近,明显优于20钢。     

Effect of Al content on high temperature erosion properties of arc-sprayed FeMnCrAl/Cr_3C_2 coatings

Three types of FeMnCrAl/Cr3C2 coatings with different Al content were deposited on 20# steel substrates by the high velocity arc spraying (HVAS) process. Surface microstructures of the coatings were analyzed by optical microscopy (OM) and X-ray diffractometry (XRD). High temperature erosion (HTE) tests were performed in an erosion tester at different impact angles. The surface morphologies of the eroded coatings were observed on a field emission scanning electron microscope(FE-SEM). The laminated structure is found on all the prepared coatings with the porosity and oxide fraction in the coatings decreasing with the Al content from 0 to 15% (mass fraction). Sample FA3 with 15% Al, possessing the lowest porosity and oxide fraction, has the best HTE resistance, which demonstrates that Al addition can improve the HTE resistance of the coatings. The erosion rate of sample FA1 exhibits a maximum value at 90° impact angle. The maximum erosion rates of both FA2 and FA3 samples appear in the range of 60°-90° impact angles. Erosion loss of the coatings occurs through brittle breaking, cutting and fatigue spalling.     

激光重熔对电弧喷涂含非晶相铁基涂层性能的影响

目的提高电弧喷涂含非晶相Fe基涂层的抗冲蚀及耐腐蚀性能。方法采用YAG脉冲激光器对电弧喷涂含非晶相Fe基涂层进行激光重熔处理。通过X-ray、SEM、冲蚀磨损和电化学等检测手段,研究该涂层重熔后的组织结构、冲蚀磨损性能和耐腐蚀性能。结果电弧喷涂含非晶相Fe基涂层经激光重熔后发生了晶化,并随着功率的增加,非晶含量降低,硬度也降低。重熔后,涂层与基体的结合方式由之前的机械咬合转变为冶金结合,涂层的致密度明显提高,组织缺陷减少。与喷涂层相比,0.3k W激光重熔涂层的抗冲蚀性能在30°攻角下可提高3倍,在90°攻角下可提高将近6倍。重熔层的冲蚀磨损机制在低冲角时以显微切削为主,高冲角时则以挤压破碎为主。随着激光功率的增加,重熔涂层的抗冲蚀性能降低。同时,在3.5%NaCl溶液中,重熔层的耐蚀性能随重熔激光功率的提高而提高,并且重熔层的腐蚀电流密度比喷涂层明显降低。结论激光重熔不但改善了电弧喷涂含非晶相Fe基涂层与基体间的结合状态,同时也增强了涂层的耐蚀和耐磨性能,是一种有效提升涂层性能的后处理工艺。     

Microstructures and erosion resistance of plasma-sprayed WCp/NiCrBSi composite coatings

WCp/NiCrBSi composite coatings have been deposited by plasma spraying with the mixed powders of WC-12Ni and NiCrBSi. The coatings consist mainly of WC, γ-Ni, Ni3B, CrB, Cr2B, M7C3, M23C6 and W2C phases. The W2C content increases with increasing WC mass fraction in the powders. The porosity and microhardness of the coatings are related to the coating WC content. The excessive WC results in decreasing the microhardncss due to increasing the porosity. The WCp/ NiCrBSi coating with 35 % WC mass fraction powder has more excellent erosion resistance. With an increase of impact angles from 15°to 90°the erosion rate of the coating increases, the erosion rate at 15°impact angle being approximately two times lower than that at 90°impact angle. Based on the wear morphology of the coatings at different impact angles, the wear mechanisms were discussed.     

Synthesis and Erosion Behaviors of Nanoscale Coatings Prepared by Wire Arc Spraying

The effects of erosive parameters,such as impact angles and environment temperature,on erosion properties of FeBSiCrMnNb nanoscale coatings were investigated.A series of coatings were prepared by wire arc spraying process.The microstructure of the coating consists of amorphous andα(Fe,Cr)nanocrystalline phase.The nanocrystals with average size of 39 nm are homogenously dispersed in amorphous matrix.The erosion results reveal that the coating exhibits better erosion resistance at lower impact angle.The erosion rates of the coating decrease as function of environment temperature.The relatively erosion resistance of the nanoscale coating is 3.7 times higher than that of AISI1045 steel substrate at 650°C.The main failure mechanism of the coating is brittle fracture.     

电站锅炉防护用Fe-Al/Cr3C2涂层性能研究及应用

使用高速电弧喷涂技术结合Fe-Al/Cr3C2粉芯丝材制备了铁铝金属间化合物涂层,对涂层的常温与高温性能进行了研究,并进行了应用的探索.结果表明,Fe-Al/Cr3C2复合涂层具有典型的层状结构、较高的结合强度和硬度;涂层的耐高温冲蚀性能良好,温度升高、角度增大,冲蚀性能提高;由于Cr2O3的存在以及涂层结合能的提高,Fe-Al/Cr3C2涂层的高温抗腐蚀性能较高;其常温和高温耐磨损性能也较高;应用研究表明,该涂层适合用于电站锅炉＂四管＂的防护.     

Microstructural Characteristics and Residual Stresses in Arc-Sprayed Cermet Coatings Using Different Carbide Grain Size Fractions

Different studies have emphasized the technological relevance of residual stresses in engineered surfaces, such as thermally sprayed coatings, and their effect on the fracture and fatigue behavior. In arc-sprayed coatings, the microstructural characteristics and resulting residual stresses are determined primarily by the inherent process characteristics and feedstock material. With the scope of this work, a study on the residual stress field in coatings formed by an arc spraying process for different electric parameter settings has been carried out using different wire configurations. Thus, iron-based cored wires with different grain-sized tungsten carbides as filler material were used as feedstock. The coatings are mainly composed of eutectic carbides, and eta carbides such as M₆C, M₁₂C, or M₂₃C and some iron-rich oxide phases, as well as characterized by an inhomogeneous, lamellar microstructure. The results demonstrated that the magnitude of the residual stresses in the coating depends on the carbide grain size fraction used as filling for cored wires. A smaller carbide grain size leads to a more pronounced dissolution of eutectic carbides, resulting in the formation of eta carbides, which in turn is accompanied by decreased tensile residual stresses across the coating. With respect to the spray parameter settings, reduced tensile residual stresses are observed when an increased voltage is applied, which can be attributed to phase evolution phenomena during spraying and thermal effects on the substrate-coating system.     

Erosion wear behaviour of plasma sprayed NiCrSiB/Al2O3 composite coating

In this work, 60 wt.% NiCrSiB–40 wt.% Al₂O₃ composite coating was produced on AISI 304 substrate material using the atmospheric plasma spraying technique. The coating surface has been characterised using a scanning electron microscope (SEM), optical microscope and X-ray diffractometer (XRD). The microhardness, porosity, density and surface roughness of the coating were measured. The adhesion strength of the coating was measured using pull off adhesion tester. The erosion behaviour of plasma sprayed coating was studied at 450 °C using hot air jet erosion testing machine. The erosion rate of coated and uncoated samples was evaluated at 30° and 90° erodent impact angles. The SEM images of the eroded samples were taken to analyse the erosion mechanism. The test results reveal that the coating protects the substrate at both 30° and 90° impact angles.