Characterization of plasma sprayed Fe-10Cr-10Mo-(C,B) amorphous coatings

Alloys of Fe-10Cr-10Mo containing a large amount of carbon and/or boron were plasma sprayed by low-pressure plasma spraying (LPPS) and high-energy plasma spraying (HPS). The as-sprayed coatings obtained by the LPPS process are composed of only an amorphous phase, while as-sprayed coatings obtained by the HPS process are a mixture of amorphous and crystalline phases. The amorphous phase in these coatings crystallizes on tempering at about 773 to 873 K, and the crystallization temperatures depend on the content of carbon and boron. Thermal stability of the amorphous phase containing boron is higher than those phases containing carbon. A very fine mixed structure of ferrite and carbide, borocarbide, or boride is formed by decomposition of the amorphous phase, bringing about a hardness of 1200 to 1400 DPN (Vickers hardness). The coatings containing carbon retain a hardness of more than 1000 DPN, even on tempering at temperatures of 1073 K or higher. The anodic polarization behavior of the coatings exhibits an activation-passivation transition in 1N H₂SO₄ solution. The active and passive current densities of the as-sprayed amorphous and tempered crystalline coatings containing carbon is lower than the coatings containing boron. The corrosion resistance of the as-sprayed and crystallized coatings containing carbon is superior to a SUS316L stainless steel coating.     

Thermal-sprayed Fe-10CM3P-7C amorphous coatings possessing excellent corrosion resistance

An alloy of Fe-10Cr-13P-7C was thermally sprayed by three different processes: (1) 80 kW low-pressure plasma spraying (LPPS), (2) high-velocity oxyfuel (HVOF) spraying, and (3) 250 kW high-energy plasma spraying (HPS). The as-sprayed coating obtained by the LPPS process was composed of an amorphous phase. In contrast, the as-sprayed coatings obtained by the HVOF and HPS processes were a mixture of amorphous and crystalline phases. The as-sprayed coatings showed a high hardness of 700 DPN. A very fine structure composed of ferrite, carbide, and phosphide was formed, producing a maximum hardness of greater than 1000 DPN in the LPPS coating just after crystallization on tempering. The corrosion re-sistance of the amorphous coating was superior to a SUS316L stainless steel coating in 1N H₂SO₄ solution and 1N HC1 solution. Furthermore, the amorphous coating underwent neither general nor pitting corro sion in1NUCI solution and 6% FeCl₃ 6H₂O solution containing 0.05N HCl, whereas the SUS316L stain less steel coating was attacked aggressively.     

Formation of amorphous Fe-Cr-Mo-8P-2C coatings by the high velocity oxy-fuel process

Alloy powders of Fe-10%Cr-8%P-2%C(10Cr), Fe-20%Cr-8%P-2%C(20Cr), and Fe-10%Cr-10%Mo-8%P-2%C(10Mo) compositions (in mass%) were sprayed by the high velocity oxy-fuel (HVOF) process under different conditions. The as-sprayed coatings of 10Mo alloy were composed of only an amorphous phase under all the spray conditions, while the as-sprayed coatings of the 10Cr and 20Cr alloys consisted of an amorphous phase with a small amount of crystalline material. The volume fraction of the crystalline material increased slightly with the rise of the flame temperature. The hardnesses of the as-sprayed coatings of the 10Cr and 20Cr alloys were 600 to 700 DPN, respectively, while the 10Mo coating composed of an amorphous phase revealed 560 DPN. The corrosion resistance of the as-sprayed coating of the 10Mo alloy was the best among three amorphous coatings and also superior to the nickel-base self-fluxing alloy and SUS316L stainless steel coatings in 1N H₂SO₄ and 1N HCl solutions.     

Erosion-resistance of plasma sprayed coatings

Cr₃C₂/NiCr, ZrO₂/NiCr, WTiC₂/NiCr, and X40 were plasma sprayed on the substrate 1Cr18Ni9Ti in order to solve the erosion wear at high temperature encountered in the oil-refining industry. A series of properties of the coatings, including their microstructure, hardness, and erosion-behavior, have been tested. The test results show that the properties of the coatings have a significant effect on their erosionresistant performance. Good erosion-resistant materials need to be hard and tough. Both Cr₃C₂/NiCr and X40 have good erosion resistance at elevated temperature.     

等离子喷涂Fe-基非晶复合涂层的磨损和腐蚀机制的研究

本文采用一种新型的气体多通道送粉等离子喷涂技术制备得到了含有不同质量分数的ZrO₂/Fe基非晶复合涂层。采用该技术可成功制得ZrO₂颗粒均匀分布于非晶基体的复合涂层,且可实现第二相颗粒的比例调控。磨损实验表明,复合涂层的磨损性能较单一的Fe基涂层有了很大提高。同时,ZrO₂颗粒的添加可提高耐蚀性能降低孔隙率。经实验表明,复合涂层的最佳耐蚀性能为ZrO₂含量50%。     

Comparison of a cold-sprayed and plasma-sprayed Fe25Cr20Mo1Si amorphous alloy coatings on 40Cr substrates

The purpose of this paper is to examine whether cold spraying is capable of manufacturing high-quality ferrous-based amorphous alloy coatings by comparing the performance of a cold-sprayed with a plasma-sprayed Fe25Cr20Mo1Si amorphous coating on a 40Cr substrate. The hardness, microstructure, wear resistance, and corrosion resistance of the two coatings were determined with potentiodynamic polarization curves, neutral salt spray tests, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction and their performance differences were examined. The results show that the cold-sprayed Fe25Cr20Mo1Si coating has an amorphous content of 97.63%, which is slightly higher than that for the raw powder (97.24%) and plasma-sprayed coating (96.55%). The coating hardness ranges from 720 HV to 1,030 HV, which is higher than plasma-sprayed coating (590–610 HV) and decreases the wear rate to about 2/3. The average porosity is 2.97 ± 0.59%, which is lower than that of the plasma-sprayed coating (4.95 ± 0.13%). The cold-sprayed Fe25Cr20Mo1Si coating can pass the 3,000 hr neutral salt spraying test, while the plasma-sprayed coating fails within 120 hr. The corrosion current in 3.5% NaCl solution reached to its stable value about 1.66 A/cm², which is about 1/4 of the plasma-sprayed coating (5.81 A/cm²). Upon analyzing the properties and the anticorrosion performance, it was found that there are no through-thickness pores in the cold-sprayed coating that impact its long-term anticorrosion performance. Cold spraying can be used to fabricate ferrous-based amorphous coatings instead of traditional thermal spraying technologies to obtain high-quality ferrous-based amorphous coatings.     

等离子弧喷涂法制备铁基非晶合金的研究

非晶态合金具有强度、韧性以及耐磨性能优于普通晶态金属材料,耐蚀性好,磁抗小等优点,倍受材料科学和工程技术人员的关注,但是非晶态材料只有在非平衡条件下才能形成,加工难度大,阻碍了非晶态材料的发展和应用.对此,采用等离子弧喷涂方法制备铁基非晶合金,制备了Fe79Si10B11非晶态合金.对制备的非晶合金进行了XRD和TEM分析,并研究了喷涂过程中粒子的飞行温度和速度,通过传热学方法计算了喷涂过程中的粉末冷却速度.结果表明,所制备的非晶合金组织均匀,喷涂过程冷却速度达4.16×107 K/s.     

医用镁合金等离子喷涂羟基磷灰石涂层研究

为了提高医用镁合金的表面耐蚀性和生物相容性,采用等离子喷涂技术在镁合金表面制备羟基磷灰石(HA)涂层.研究结果表明,镁合金表面所制备的HA涂层与基体结合牢固,界面无裂纹、气孔等缺陷.相组成为生物相容性较好的HA和少量的Ca3(PO4)2(TCP),显微组织具有层状特征,涂层表面存在一些有利于骨长人的孔隙.涂层的弹性模量约为19.825 GPa,接近骨的弹性模量,涂层表面硬度为300～350 HV.腐蚀试验和钙磷沉积试验结果表明HA涂层具有较好的耐蚀性和骨诱导性.     

铝镁合金等离子喷涂复相陶瓷涂层微观组织

为解决铝镁合金表面耐磨性差的问题,利用机械球磨法和PVA造粒技术制备复合陶瓷粉末,采用等离子喷涂技术在XGFH-3铝镁合金表面制备了反应复相陶瓷涂层,利用扫描电镜(SEM)、X射线衍射仪(XRD)分析了喷涂复合粉末和复相陶瓷涂层的形貌及组成.结果表明,复合粉末随着球磨时间的延长明显趋于扁平化和均匀化,并且生成了Al₃Ti,Ni₄Ti₃等新相.而在喷涂过程中Al₃Ti和Ni₄Ti₃中间相又会消失,涂层中出现了MgAl₂O₄和Ti₅Si₃等新相,基体和涂层之间有元素扩散,这使得涂层有良好的结合强度.     

On-line temperature monitoring and process diagnosis of plasma sprayed coatings

On-line temperature monitoring of plasma sprayed coating is presented, which is based on IR pyrometery combined to robot trajectories. Temperature fields of the substrate before spraying and the deposited coating when the damage happens are taken to investigate the temperature fluctuation information. Experimental results demonstrate that coating damage always occurs in the temperature transition area of the substrate from the higher to the lower, as well as the higher temperature area. The temperature difference between the peak and the mean of the relevant regions is beyond 30-50 ℃ or even higher. This case provides the omen of coating damage and the focusing scopes for the process control of coating temperature in plasma spraying.     

Fe基非晶合金涂层的等离子喷涂成形特征

采用大气等离子喷涂法在Q235钢基材表面制备了Fe基非晶合金涂层，研究表明，涂层基本上由非晶相组成，在涂层中分布着少量的尺寸为2-5μm的淬态核结晶相，涂层中氧化物的含量较少。涂层由条带状粒子相互搭接、逐层堆积而成，具有典型的层状结构形貌。尺寸约为60μm的球形喷涂粒子在涂层中变形为高度尺寸约为6μm扁平状粒子，保证了高非晶相含量涂层的顺利形成。在涂层中的粒子边界还包含着少量的孔隙、微细的球形粒子等缺陷。涂层与基材、涂层中粒子问主要以机械结合为主，涂层与基材的结合区为涂层-基材体系中的最薄弱处。     

Wear and corrosion resistance of laser remelted and plasma sprayed Ni and Cr coatings on copper

Nickel and chromium coatings were produced on the copper sheet using plasma spraying and laser remelting. The sliding wear test was achieved on a block-on-ring tester and the corrosion test was carried out in an acidic atmosphere. The corrosive behaviors of both coatings and original copper samples were investigated by using an impedance comparison method. The experimental results show that the nickel and chromium coatings display better wear resistance and corrosion resistance relative to the original pure copper sample. The wear resistance of the coatings is 8 - 12 times as large as original samples, and the wear resistance of laser remelted samples is better than that of plasma sprayed ones. The corrosion resistance of laser remelted nickel and chromium samples is better than that of plasma sprayed samples respectively. The corrosion rate of chromium coatings is less than that of nickel coatings, and the laser remelted Cr coating exhibits the least corrosion rate.     

等离子喷涂过程中粒子的氧化及其对涂层性能的影响

利用粒子收集装置和附加氩气保护罩,研究了铁粒子和NiCoCrAlY粒子在等离子喷涂过程中的氧化行为及其对涂层性能的影响.结果表明,粒子在飞行过程中存在对流氧化和扩散氧化两种氧化机制,粒子的氧化方式取决于离开喷嘴的距离;离开喷嘴距离越长,粒子氧化越严重;采用附加氩气保护罩能明显减少喷涂过程中外界空气对粒子的氧化,降低涂层孔隙率,提高NiCoCrAlY涂层的抗高温氧化性能.

Abstract：

The oxidation mechanisms of iron particles and NiCoCrAlY particles during plasma spraying process and its effect on the sprayed coatings were investigated by the in-flight particles collection setup and the gas shrouding. The results show that there are two oxidation mechanisms during in-flight oxidation: one is the diffusion oxidation; the other is the convective oxidation, which are decided by the distance from the spraying particles to the nozzle. The oxidation content increases with the increasing of the standoff distance. The shrouded gas can decrease the oxidation content of inflight particles and increase the oxidation resistance of NiCoCrAIY coatings.     

超音速等离子喷涂非晶涂层微观结构与摩擦学性能

采用新一代超音速高能等离子喷涂(SAPS)技术制备了Fe基和Mo基两种非晶涂层,对涂层的微观结构与摩擦学性能进行对比分析。结果表明,SAPS喷涂Fe基和Mo基非晶涂层内部孔洞少、结构致密性高。与Fe基涂层相比,具有更低孔隙率的Mo基涂层在摩擦过程中表现出更低的磨损率(1.1×10^-4 μm·N^-1·s^-1),耐磨性更优。涂层的磨损机理均以磨粒磨损和疲劳磨损为主,并伴随着磨屑氧化。     

Effect of processing parameters on the microstructures and corrosion behaviour of high‐velocity oxy‐fuel (HVOF) sprayed Fe‐based amorphous metallic coatings

A FeCrMoMnWBCSi amorphous metallic coating was prepared by using high‐velocity oxy‐fuel spray. The influence of processing parameters on microstructure, porosity level, amorphous phase fraction and corrosion behaviour of the coatings was characterised by scanning electron microscopy, X‐ray diffraction, differential scanning calorimeter and electrochemical methods. The results indicated that the microstructures of the coatings were sensitive to the spray parameters considerably. Porosity and unmelted particle proportion decreased with the oxygen/fuel (O/F) ratio and increased with the powder feed rate. The trend of oxides content was opposite to the porosity and unmelted particle proportion. The coatings obtained with higher O/F ratio and lower powder feed rate exhibited higher hardness. The low coating hardness was mainly due to the high porosity especially when the porosity was higher than 1.21%. The spraying parameters strongly affected the amorphous phase fraction. There was a critical passive current density for balancing the porosity and the amorphous phase fraction. Corrosion resistance is dominant by the amorphous phase fraction when the porosity is less than 1.21%, while by porosity when it is higher than that. Open‐circuit potential, potentiodynamic polarisation and electrochemical impedance spectroscopy results showed that the coatings obtained with the O/F ratio of 4.2 and the powder feed rate of 40 g/min exhibiting the best corrosion resistance in 1 wt% sodium chloride solution.     

Characterization of mechanical properties of suspension plasma sprayed TiO2 coatings using scratch test

The study aimed at characterizing mechanical properties of TiO₂ coatings obtained by the use of aqueous suspensions of fine rutile and anatase particles onto metal substrates. Thickness of the coatings was found with the use of optical microscope observations of metallographical cross-sections. The coatings morphology was found with scanning electron microscope (SEM) and their phase composition was determined by X-ray diffraction method. The mechanical properties were characterized using scratch test. The test enabled to characterize the adhesion of coatings by determination of critical force necessary to peel off the coatings from the substrate and, on the other hand, to estimate their cohesion by the measurement of the scratch hardness. The hardness was calculated using the width of the scratch and the value of force applied. The design of experiments (DOE) of spraying with the use of a 2³ full factorial plan was applied to rutile powder. The coatings were sprayed onto aluminium substrate. The DOE enabled to find the effects of three principal parameters, i.e. electric power input to plasma, spray distance and suspension feed rate onto coating adhesion expressed by critical force. A preliminary data for anatase powder sprayed with one set of operational parameters onto stainless steel substrate are also shown.     

Fe基非晶合金的晶化及其在NaCl溶液中的电化学腐蚀行为

采用单辊甩带法制备出完全非晶态的Fe_(78)Si_(13)B_9和Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1薄带,并利用非晶晶化退火法制备非晶和纳米晶双相合金Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1薄带.利用X射线衍射仪和示差扫描量热计对该非晶薄带的非晶特性及其晶化过程进行研究,并用电化学极化曲线的方法和电化学阻抗技术对比研究非晶Fe_(78)Si_(13)B_9和双相合金Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1在1 mol/L NaCl溶液里的电化学腐蚀行为,用SEM对极化测试后的试样形貌进行观察;同时还研究不同的热处理温度对材料的结构及在1 mol/L NaCl溶液里耐腐蚀性能的影响.结果表明:该非晶薄带的晶化过程分为两步;双相合金比非晶合金的耐腐蚀性要好;随着热处理温度升高,非晶合金和双相合金的耐腐蚀性能都得到提高.     

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。     

铬锆铜表面等离子喷涂Cr3C2p/NiCr涂层的组织与性能

采用等离子喷涂技术在铬锆铜(CrZrCu)基体表面制备了Cr3C2 p/NiCr涂层。利用X射线衍射仪(XRD)、扫描电镜(SEM)等仪器研究了涂层的显微组织及结构,采用磨粒磨损试验机对Cr3C2 p/NiCr涂层与电镀NiCo层的磨损性能进行了测试比较。结果表明:涂层组织呈片层状结构,在NiCr合金片层上分布着未熔的Cr3C2和Cr7C3、Cr2Ni3、CrNi析出相。与电镀Ni-Co镀层相比,Cr3C2 p/NiCr涂层具有较高的硬度和耐磨粒磨损性能,其磨损量仅为电镀层的35%。     

铁基非晶态合金涂层表面耐磨损及耐腐蚀性能研究

铁基非晶态合金凭借优异的耐磨和耐腐蚀性能在石油、煤电、钢铁和船舶等领域得到广泛应用。本文利用超音速火焰喷涂工艺在316不锈钢基体上制备铁基非晶态合金涂层,研究了涂层的磨削性能、涂层磨削表面的耐磨性能和耐腐蚀性能。研究结果表明三个磨削参数中,磨削深度对涂层表面的表面粗糙度及耐腐蚀性能影响最大,进给速度次之;而进给速度对涂层表面耐磨性能影响最大,磨削深度次之;磨削速度对涂层表面的表面粗糙度、耐磨性能和耐腐蚀性能影响较小。最后,根据不同的涂层性能要求对磨削参数组合进行优化。