Characterization of plasma sprayed Fe-17Cr-38Mo-4C amorphous coatings crystallizing at extremely high temperature

A Fe-17Cr-38Mo-4C alloy powder was plasma sprayed by three processes: an 80 kW low-pressure plasma spray (LPPS), a 250 kW high-energy plasma spray (HPS), and a 40 kW conventional plasma spray (APS). The as-sprayed coating obtained by the LPPS process is composed of only amorphous phase. As-sprayed coatings obtained by the HPS and APS processes are a mixture of amorphous and crystalline phases. The three as-sprayed coatings exhibit a high hardness of 1000 to 1100 DPN. The amorphous phase in these coatings crystallizes at a high temperature of about 920 K. A very fine structure composed of hard ϰ-phase and carbides is formed after crystallization. The hardness of the coating obtained by LPPS reaches a maximum of 1450 DPN just after crystallization on tempering and retains a high hardness more than 1300 DPN after tempering at high temperatures of 1173 or 1273 K. The corrosion potential of the amorphous coating is the highest among the three coatings and higher than that of a SUS316L stainless steel coating. The anodic polarization measurements infer that the corrosion resistance of the amorphous coating is superior or comparable to SUS316L stainless steel coating in H₂SO₄ solution.     

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.     

电弧喷涂铁基非晶涂层摩擦磨损性能分析

采用电弧喷涂技术在低碳钢基体上制备Fe-（Cr,Ni）-（C,B）系非晶合金涂层。利用X射线衍射仪、扫描电子显微镜和差热分析仪对涂层的相组成、微观组织和热稳定性进行了分析,用MRH-3型高速环块磨损试验机研究涂层的干摩擦磨损行为.结果表明,涂层中含有一定量的非晶相,呈典型的热喷涂层状组织结构,孔隙率较低;涂层具有良好的热稳定性,在500℃以下使用不会发生晶化转变;涂层具有较高的显微硬度和优异的摩擦磨损性能,平均显微硬度为1 155 HV0.1,相同试验条件下,涂层的相对耐磨性能约为Q235钢的13.3倍,涂层的磨损机制主要以疲劳磨损为主.     

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.     

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.     

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。     

电弧喷涂铁基非晶涂层的结构与性能

用电弧喷涂技术在低碳钢基体上制备一种含非晶和纳米晶的Fe基涂层.采用X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、显微硬度仪分析测量涂层的组织和性能.并用谢乐公式计算晶粒尺寸.结果表明,涂层呈典型的层状组织结构,由变形良好的带状粒子相互搭接堆积而成.涂层结构致密,孔隙率低,氧化物含量较少,涂层含有非晶和纳米晶,晶粒尺寸为10~40 nm,利用X射线衍射强度比较法测量涂层中非晶相的含量为55.3%.涂层具有很高的硬度,其显微硬度最高达到1 260 HV0.1.     

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.     

非晶铝基粉末冷喷涂涂层及其耐磨性能

为提高镁合金的耐磨性能,采用冷喷涂技术在AZ91D镁合金表面制备铝基非晶涂层,并利用扫描电镜对涂层的微观形貌进行分析,采用X射线衍射仪分析喷涂粉末及涂层中的非晶含量,利用多功能摩擦磨损试验机研究了涂层的耐磨性能。结果表明:冷喷涂后涂层中仍含有铝基非晶结构,非晶含量为48%,涂层微观组织致密,孔隙率为0.59%。铝基非晶涂层的磨损量和磨损率均低于镁合金基体,摩擦因数高于基体。     

等离子喷涂制备铁基非晶涂层及其耐磨性

采用等离子喷涂的方法制备铁基非晶涂层,并对不同喷涂功率制备涂层的组织和耐磨性进行了分析。结果表明,3种功率制备涂层表面致密、孔隙率低,且具有较高的热稳定性、硬度和耐磨性。当喷涂功率为30 k W时,涂层非晶程度高;喷涂功率为35和40 k W时,涂层中有Fe2B和Mo6Co6C晶相出现,随喷涂功率增加,涂层硬度和摩擦因数升高,35 k W制备涂层的耐磨性最好。     

喷涂工艺参数对硅灰石涂层结构的影响

采用等离子喷涂方法,在不同喷涂距离、主气流量和喷涂功率下制备硅灰石涂层.使用扫描电镜观察了涂层的微观形貌,研究了喷涂工艺参数对涂层结构的影响.结果表明,在较大主气流量下,随着喷涂距离增加,涂层粒子扁平化程度降低,涂层内孔隙逐渐增多;在较小主气流量下,涂层粒子扁平化程度随喷涂距离增加呈现先增加后减小的趋势.主气流量增加,涂层致密,粒子扁平充分.喷涂功率增加,粒子熔化好,涂层致密;但随喷涂功率进一步增加,涂层中出现较多的圆形孔隙.喷涂工艺参数对涂层结构的影响主要通过影响熔融粒子的温度和速度所致.     

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。