Abrasive wear resistance of plasma-sprayed glass-composite coatings

A ball-milled mixture of glass and alumina powders has been plasma sprayed to produce alumina-glass composite coatings. The coatings have the unique advantage of a melted, ceramic secondary phase parallel to the surface in an aligned plateletlike-composite structure. The alumina raises the hardness from 300 HV for pure glass coatings to 900 HV for a 60 wt.% alumina-glass composite coating. The scratch resistance increases by a factor of 3, and the wear resistance increases by a factor of 5. The glass wears by the formation and intersection of cracks, while the alumina wears by fine abrasion and supports most of the sliding load. The wear resistance reaches a maximum at 40 to 50 vol.% alumina, above which there is little further improvement. This critical alumina content corresponds to the changeover from a glass to a ceramic matrix.     

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.     

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。     

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.     

超音速等离子喷涂沉积可磨耗封严涂层研究

采用超音速等离子喷涂沉积Ni-C及NiCr-BN可磨耗封严涂层,通过实验对比研究两种涂层的结合强度、表面硬度及在不同冲蚀角下的冲蚀磨损性能.结果表明:NiCr-BN涂层中的润滑相尺寸比Ni-C涂层更为细小;NiCr-BN涂层的结合强度及表面硬度均高于Ni-C涂层;NiCr-BN涂层的抗冲蚀性能要优于Ni-C涂层.     

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.     

Dry sliding wear behavior of ceramic-metal composite coatings prepared by plasma spraying of self-reacting powders

Ceramic-metal composite (CMC) coatings were deposited on the surface of Fe-0.14–0.22 wt.% C steel by plasma spraying of self-reacting Fe₂O₃−Al composite powders. The dry sliding friction and wear character of the CMC coatings are investigated in this paper. The wear resistance of the CMC coatings was significantly better than that of Al₂O₃ coatings under the same sliding wear conditions. The tough metal, which is dispersed in the ceramic matrix, obviously improved the toughness of the CMC coatings. Wear mechanisms of the CMC coatings were identified as a combination of abrasive and adhesive wear.     

等离子喷涂纳米Al_2O_3-TiO_2-SiO_2-SiC涂层抗热震性能

将纳米结构Al2O3、TiO2、SiO2、SiC粉体经液相喷雾造粒的方法,制备出适合等离子喷涂的球形复合粉体,采用等离子喷涂技术制备出含纳米结构的陶瓷涂层.通过水淬法,将涂层试样分别经500、700、900和1 100 ℃加热并保温10 min,然后投入冷水中以测量其抗热震能力,通过宏观和SEM照片加以观察,分析其失效的机理.试验结果表明,该纳米结构涂层在较低温度( ＜700 ℃)具有优良的抗热震性能.     

Effect of substrate temperature on adhesion strength of plasma-sprayed nickel coatings

We plasma-sprayed nickel coatings on stainless steel and cobalt alloy coupons heated to temperatures ranging from room temperature to 650 °C. Temperatures, velocities, and sizes of spray particles were recorded while in-flight and held constant during experiments. We measured coating adhesion strength and porosity, photographed coating microstructure, and determined thickness and composition of surface oxide layers on heated substrates. Coating adhesion strength on stainless steel coupons increased from 10–74 MPa when substrate temperatures were raised from 25–650 °C. Coating porosity was lower on high-temperature surfaces. Surface oxide layers grew thicker when substrates were heated, but oxidation alone could not account for the increase in coating adhesion strength. When a coupon was heated to 650 °C and allowed to cool before plasma-spraying, its coating adhesion strength was much less than that of a coating deposited on a surface maintained at 650 °C. Cobalt alloy coupons, which oxidize much less than stainless steel when heated, also showed improved coating adhesion when heated. Heating the substrate removes surface moisture and other volatile contaminants, delays solidification of droplets so that they can better penetrate surface cavities, and promotes diffusion between the coating and substrate. All of these mechanisms enhance coating adhesion.     

等离子喷涂Al-Mo涂层的高温硫化和氧化行为研究

烧嘴是水煤浆气化系统的重要部件。运行过程中的高温硫化经常导致烧嘴提前失效,进而影响设备的安全稳定运行。本文采用等离子喷涂方法制备了Mo为粘结层的Al-Mo涂层,测量其在973 K, 1073 K and 1173 K的硫化和氧化行为,并与Mo涂层和Inconel合金进行比较。结果表明Al-Mo涂层的高温硫化抗力和氧化抗力均优于Mo涂层,高温硫化抗力优于Inconel合金。该涂层的提出为喷嘴失效问题的解决提供了便捷、有效的技术方案。     

Wear characteristics of plasma-sprayed nanostructured yttria partially stabilized zirconia coatings

Reconstituted nanostructured and conventional yttria partially stabilized zirconia coatings were deposited by atmospheric plasma spray. The tribologic properties of the coatings against 100C6 steel were evaluated with a ball-on-disc configuration under dry friction conditions at room temperature. Microstructure and the phase composition of the powders and the coatings were examined using a scanning electron microscope, optical microscope, and x-ray diffraction. Microhardness and the Young’s modulus of coatings were measured by indentation testing. Results showed that the wear resistance of the coatings produced using the nanostructured powder is improved compared with the coating produced using the conventional powder. The wear rates of nanostructured zirconia coatings are about four-fifths of those of conventional counterparts under a load of 5 N. The wear mechanism is also discussed. The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf, Germany.     

等离子喷涂氧化锆涂层及激光重熔涂层的摩擦磨损性能

采用等离子喷涂制备了常规氧化锆涂层和纳米氧化锆涂层,并对制备的纳米氧化锆涂层进行了激光重熔处理,系统地研究了3种氧化锆涂层(常规、纳米和激光重熔涂层)在常温和高温下的摩擦磨损性能.结果表明,纳米氧化锆涂层耐磨性能明显优于常规氧化锆涂层,而激光重熔处理后的纳米氧化锆涂层在常温和高温下,都表现出最低的摩擦系数和最好的耐磨性能.这3种涂层的表面粗糙程度、涂层孔隙率和裂纹状况明显不同,从而表现出不同的摩擦磨损特性;说明纳米粉末等离子喷涂结合激光重熔技术是提高氧化锆涂层性能的有效方法.     

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.     

退火晶化对化学沉积Ni-W-P合金镀层耐磨性的影响

用化学沉积法制备Ni-W-P合金镀层。利用扫描电镜(SEM)及X射线衍射(XRD)技术,并结合JADE软件定量分析镀层微观组织特征,研究了退火晶化前后显微组织对镀层耐磨性的影响。结果表明,化学沉积Ni-5.24wt%W-6.71wt%P镀层镀态下的晶化程度约为24%,退火温度升高到700℃时,晶化程度约为94%,未达到完全晶化。在Ni3P相晶化反应温度下,Ni3P相的晶粒尺寸大于Ni相,高于其晶化温度时,Ni相晶粒尺寸大于Ni3P相。退火温度超过600℃时,两相的晶粒尺寸迅速粗化。镀层磨损率随退火温度的升高而减小,500℃时出现最小值,超过500℃时,磨损率又开始增大。镀层较高的耐磨性除了与其硬度有关外,还取决于适当的晶化程度和较小的晶粒尺寸。     

Structure and wear resistance of TiN and TiAlN coatings on AZ91 alloy deposited by multi-arc ion plating

In order to investigate the microstructure of TiN and TiAlN coatings and their effect on the wear resistance of Mg alloy, TiN and TiAlN coatings were deposited on AZ91 magnesium alloy by multi-arc ion plating technology. TiN and Ti70Al30N coatings were prepared on the substrate, respectively, which exhibited dark golden color and compact microstructure. The microstructures of TiN and Ti70Al30N coatings were investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The micro-hardness and wear resistance of TiN and Ti70Al30N coatings were investigated in comparison with the uncoated AZ91 alloy. The XRD peaks assigned to TiN and TiAlN phases are found. The hardness of TiN coatings is two times as high as that of AZ91 alloy, and Ti70Al30N coating exhibits the highest hardness. The wear resistance of the hard coatings increases obviously as result of their high hardness.     

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%。     

Reactive HVOF sprayed TiN-matrix composite coating and its corrosion and wear resistance properties

TiN-matrix composite coating was prepared on 45# steel by reactive high-velocity oxy-fuel (HVOF) spraying. Its microstructure, phase composition, micro-hardness, corrosion resistance in 3.5% NaCl solution and wear resistance were analyzed. The results suggest that the TiN-matrix composite coating is well bonded with the substrate. The micro-hardness measured decreases with the increase of applied test loads. And the micro-hardness of the coating under heavy loads is relatively high. The TiN-matrix composite coating exhibits an excellent corrosion resistance in 3.5% NaCl solution. The corrosion potential of coating is positive and the passivation zone is broad, which indicates that the TiN-matrix composite coating is stable in the electrolyte and provides excellent protection to the substrate. The wear coefficient of the coating under all loads maintains at 0.49–0.50. The wear mechanism of the coating is revealed to be three-body abrasive wear. Yet the failure forms of TiN-matrix composite coating under different loads have an obvious difference. The failure form of coating under light loads is particle spallation due to the stress concentration while that of coating under heavy loads is cracking between inter-lamellae.     

工业纯铜陶瓷/渗铝复合涂层制备及耐磨性

利用热化学反应法和化学热处理在工业纯铜上同时制备陶瓷/渗铝复合涂层。与热化学反应陶瓷涂层相比,复合涂层的致密度、结合强度均优于热化学反应陶瓷涂层。封孔后耐磨粒磨损性能是基体的4.05倍,耐粘着磨损(干摩/油摩)性能分别为基体的3.67倍和10.43倍。     

Improvement of corrosion resistance of high-velocity oxyfuel-sprayed stainless steel coatings by addition of molybdenum

To improve the marine corrosion resistance of stainless steel coatings fabricated by high-velocity oxyfuel (HVOF) spraying with a gas shroud attachment, the molybdenum (Mo) content of stainless steel was increased to form coatings with a chemical composition of Fe balance-18mass%Cr-22mass%Ni-2∼8mass%Mo. These coatings were highly dense, with <0.1 vol.% in porosity, and less oxidized, with 0.5 mass% in oxygen content at most. The corrosion mechanism and resistance of the coatings were investigated by electrochemical measurement, chemical analysis, and statistical processing. The general corrosion resistance of the coatings in 0.5 mol/dm³ sulfuric acid was improved with increases in Mo content, and the corrosion rate could be decreased to 8.8 × 10⁻² mg/cm² per hour (∼1 mm/year) at 8 mass% Mo. The pitting corrosion resistance of the coatings in artificial seawater was improved with increases in Mo content and was superior to that of the 316L stainless steel coating. The crevice corrosion resistance of the coatings in artificial seawater was improved and the number of rust spots at 4 mass% Mo was decreased to 38% of that for the 316L coating. Accordingly, Mo is highly effective in improving the corrosion resistance of the stainless steel coatings by HVOF spraying.     

铝合金基体电热爆炸喷涂钼涂层的制备工艺与性能

采用电热爆炸喷涂技术在铝合金基体上制备钼涂层,用SEM、划痕仪、显微硬度计、表面粗糙度仪、微磨损试验机等表征了涂层性能。借助正交试验方法分析了钼涂层制备中各工艺参数对涂层质量的影响,确定了最佳工艺参数。结果表明:用电热爆炸喷涂方法制备的钼涂层均匀致密,孔隙率低;涂层与基体形成冶金结合,结合强度高;涂层硬度为基体的4.9倍,体积磨损量仅为基体的11.2%,耐磨性大幅增加。电爆炸喷涂的工艺参数中,对涂层质量和结合力影响最大的是喷涂距离,其次是喷涂次数,影响最小的是喷涂电压。