反应等离子喷涂TiC/Fe-Ni金属陶瓷复合涂层的显微组织

采用前驱体碳化复合技术制备Ti-Fe-Ni-C系粉末,并通过反应等离子喷涂技术（RPS）原位合成并沉积了TiC/Fe-Ni基金属陶瓷复合涂层。利用XRD、SEM和EDS研究复合粉末和涂层的成分、组织结构,考察复合粉末的TiC含量及复合粉末粒度对涂层组织结构的影响。结果表明：采用前驱体碳化复合技术制备的反应喷涂复合粉末粒度均匀、无有害相生成;TiC/Fe-Ni复合涂层由不同含量TiC颗粒分布于晶粒内部而形成的晶内型复合强化片层叠加而成,基体主要为（Fe、Ni）固溶体,TiC颗粒呈纳米级;涂层TiC含量较高时,纳米级TiC颗粒弥散分布更均匀;喷涂粉末粒度较大时,片层厚度较大,孔隙率较高。     

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.     

Microstructures and mechanical properties of FeCoCrNi high entropy alloy/WC reinforcing particles composite coatings prepared by laser cladding and plasma cladding

FeCoCrNi HEA coatings with 20% mass fraction of WC reinforcing particles were prepared by two different cladding methods, laser cladding (LC) and plasma cladding (PC). The microstructure of HEA matrix and WC particles of LC and PC coatings were discussed respectively. For HEA matrix, dendritic morphology was observed in both coatings. For WC particles, a few granular (Cr,W)₂C carbides around WC particles in LC coatings, and a large number of crystal and fishbone Fe₃W₃C carbides around WC particles in PC coatings. Mechanical properties as hardness and wear resistance of the two kinds of coatings were also investigated. The interstitial solution strengthening effect of C element is stronger in PC coating, and the hardness of HEA matrix in LC coatings is twice that of in PC coating, which shows a strong retention force on WC particles. The friction coefficient of LC coating is lower and stable, with the volume wear rate of 0.7 × 10⁻⁵ mm⁻³/N·m, showing high wear resistance. PC coatings have poor wear resistance due to decarbonization and oxidation of WC particles and reduction of retention force of HEA matrix, with the volume wear rate of 8.29 × 10⁻⁵ mm⁻³/N·m. The wear mechanism of both coatings were also discussed.     

AI-Li/SiCp composites and Ti-AI alloy powders and coatings prepared by a plasma spray atomization (PSA) technique

There has been increasing use of Al-Li alloys in the aerospace industry, due mainly to the low density and high elastic modulus of this material. However, the problem of low ductility and fracture toughness of this material has limited its present application to only weight- and stiffness-critical components. Development of Al-Li/ceramic composites is currently being investigated to enhance the service capabilities of this material. The Ti-Al alloy is also of interest to aerospace-type applications, engine components in particular, due to its attractive high-temperature properties. Preparation of fine powders by plasma melting of composite feedstock and coatings formed by plasma spraying was carried out to examine the effect of spray parameters on the microstructure and properties of these materials. Characterization of the powders and coatings was performed using the scanning electron microscope and image analyzer. Examination of the plasma-sprayed powders and coatings has shown that in the Al-Li/SiC composite there is melting of both materials to form a single composite particle. The SiC reinforcement was in the submicron range and contributed to additional strengthening of the composite body, which was formed by a cold isostatic press and consolidated by hot extrusion or hot forging processes. The plasma-sprayed Ti-Al powder showed four categories of microstructures: featureless, dendritic, cellular, and martensite-like.     

Tungsten carbide coatings with different binders prepared by low power plasma spray system

Thermal spraying of cermet coatings is widely used for protection of machining parts against wear and corrosion. These coatings consist of WC particles in metal binders such as Co, Cr and Ni. Three kinds of WC powders with different metal binders (Co, NiCr and CoCr) were sprayed by low power plasma spray system on Al-Si-Cu alloy substrate. Fundamental aspects of sprayed cermet coatings, including (i) the effects of binder type on the coating structure, (ii) the hardness and (iii) the microstructure, were investigated. All cermet coatings have the same phase structure such as WC and W2 C. However, the intensities of these phases are different in each coating, mainly due to the difference in solidification rate in each case. Moreover, the hardness measurements are found to be different in each coating. The results show that, binder type has a significant effect on the physical and mechanical properties of the sprayed coatings.     

Properties and structure of coatings from PG-SR powders prepared by a plasma method

In recent years, a plasma method for obtaining coatings with the use of a controlled electric arc instead of an uncontrolled welding arc has found wide application in various branches of industry. The Laboratory of Materials Science at the Institute of Coal of the Siberian Branch of the Russian Academy of Sciences is working on the possibility of using plasma strengthening coatings for increasing the wear resistance of parts of mining equipment. A whole spectrum of coated parts for hydraulic supports and the equipment of concentration plants with an increased service life and wear resistance has been suggested. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 26–28, August, 1997.     

Microstructure characteristics of coating with amorphous phases prepared from Fe-based alloy powders by plasma spray

In this paper, alloy powders mixed with a molar ratio of Fe ： P ： C of 80 ： 13 ： 7 were sprayed on Q235 steel by plasma spray method to prepare coating with amorphous phases. The phase composition of the mixed alloy powders and prepared coating were characterized by X-ray diffraction （ XRD ）. The morphology and the composition cf the coating were analyzed by scanning eleetron microscopy （SEM） nnd energy dispersive apectroscopy （ EDS ）. In addition, the thermal stability ef the coating with amorphous phases was characterized by differential thermal analyzer （ DTA ）. Tile results showed that, usirtg mixed alloy powders with a molar ratio of Fe： P： C of 80：13：7, the coating containing certain amount of amorphous alloys was suceessathlly prepared through atmospheric plasma spray technique. In the coating, the main phases were determined to be Fe, FeP aad Fe2P. The crystallization of the coating started from about 461°. Tile coating was mechanically adhered to the substrate.     

Microstructure and properties of TiN/Ni composite coating prepared by plasma transferred arc scanning process

The TiN/Ni composite coatings were deposited on 7005 aluminium alloy by high speed jet electroplating and then processed with plasma transferred arc(PTA) scanning process. The microstructure, microhardness and friction coefficient of PTA scanning treated specimens were investigated. It is shown that the PTA scanning treated specimens have a rapidly solidified microstructure consisting of the uniformly distributed TiN phase and fine Al₃Ni₂ intermetallic phases. The composite coating has an average microhardness of approximately HV 800. The friction coefficient of PTA scanning treated specimens (oscillated at around 0.25) is considerably lower than that of TiN/Ni composite coating (oscillated at around 0.35). The corrosion behavior of the composite coating in 3.5% NaCl solution at room temperature was also determined using a potentiostat system. In comparison with the corrosion potential _corr of −0.753 V for 7005 aluminium alloy, the corrosion potentials for TiN/Ti composite coating and PTA scanning treated specimen are increased by 0.148 V and 0.305 V, respectively. The PTA scanning treated specimen has the lowest corrosion current densityJ_corr as well as the highest corrosion potential _corr, showing an improved corrosion resistance compared with 7005 aluminium alloy.     

Microstructures and mechanical properties of TiAl alloy prepared by spark plasma sintering

A fine-grained TiAl alloy with a composition of Ti-47%Al(mole fraction) was prepared by double mechanical milling(DMM) and spark plasma sintering(SPS). The relationship among sintering temperature, microstructure and mechanical properties of Ti-47%Al alloy was studied by X-ray diffractometry(XRD), scanning electron microscopy(SEM) and mechanical testing. The results show that the morphology of double mechanical milling powder is regular with size of 20?40 μm. The main phase TiAl and few phases Ti₃Al and Ti₂Al were observed in the SPS bulk samples. For samples sintered at 1000 °C, the equiaxed crystal grain was achieved with size of 100?250 nm. The samples exhibited compressive and bending properties at room temperature with compressive strength of 2013 MPa, compression ratio of 4.6% and bending strength of 896 MPa. For samples sintered at 1100 °C, the size of equiaxed crystal grain was obviously increased. The SPS bulk samples exhibited uniform microstructures, with equiaxed TiAl phase and lamellar Ti₃Al phase were observed. The samples exhibited compressive and bending properties at room temperature with compressive strength of 1990 MPa, compression ratio of 6.0% and bending strength of 705 MPa. The micro-hardness of the SPS bulk samples sintered at 1000 °C is obviously higher than that of the samples sintered at 1100 °C. The compression fracture mode of the SPS TiAl alloy samples is intergranular fracture and the bending fracture mode of the SPS TiAl alloy samples is intergranular rupture and cleavage fracture.     

高速电弧喷涂Fe-TiB2/Al2O3复合涂层的组织及性能

采用低碳钢包覆0～70%TiB2/Al2O3硬质相的粉芯丝材和高速电弧喷涂(HVAS)原位合成MMC涂层,分析和测试了涂层的组织、相组成及耐磨粒磨损性能.结果表明:涂层的性能由其组织和相组成决定,HVAS的非平衡制造过程在涂层中形成多种相:在Fe基固溶体上存在TiB2、Al2O3、FexB及少量的金属间化合物AlFe3和NiAl;随着TiB2及Al2O3在涂层中体积分数的增加,涂层的耐磨粒磨损性能明显提高,磨损质量损失随陶瓷相体积分数的增加呈线性减少;添加合金元素Ni和Al可降低孔隙率,增加涂层耐磨性.使用HVAS方法制备了含TiB2的高性能耐磨复合陶瓷涂层.     

Nano-sized hydroxyapatite powders prepared by flame spray pyrolysis

Pure and doped CaMnO₃ were synthesized by applying modified glycine/nitrate procedure. The detailed structural characterization of prepared nanometric size powders, their properties, as well as the results on studying sintering and microstructure of the sintered bodies are given. Since the data on additive influence on densification of CaMnO₃ during sintering are difficult to find in the literature, their role in densification is discussed. It was found that increasing Y concentration enhanced densification during sintering, and in addition, suppressed grain growth process. The results of the electrical conductivity measurements as a function of dopant concentration are also discussed.     

Tribological properties of TiC-Fe coatings obtained by plasma spraying reactive powders

Titanium carbide-based coatings have been considered for use in sliding wear resistance applications. Carbides embedded in a metal matrix would improve wear properties, providing a noncontinuous ceramic surface. TiC-Fe coatings obtained by plasma spraying of spray-dried TiC-Fe composite powders containing large and angular TiC particles are not expected to be as resistant as those containing TiC particles formed upon spraying. Coatings containing 60 vol% TiC dispersed in a steel matrix deposited by plasma spraying reactive micropellets, sintered reactive micropellets, and spray-dried TiC-Fe composite powders are compared. The sliding wear resistance of these coatings against steel was measured following the test procedure recommended by the Versailles Advanced Materials and Standards (VAMAS) program, and the inherent surface porosity was evaluated by image analysis. Results show that, after a 1-km sliding distance, TiC-Fe coatings obtained after spraying sintered reactive powders exhibit scar ring three times less deep than sprayed coatings using spray-dried TiC-Fe composite powders. For all coatings considered, porosity is detrimental to wear performance, because it generally lowers the coating strength and provides cavities that favor the adhesion of metal. However, porosity can have a beneficial effect by entrapping debris, thus reducing friction. The good wear behavior of TiC-Fe coatings manufactured by plasma spraying of sintered reactive powders is related to their low coefficient of friction against steel. This is due to the microstructure of these coatings, which consists of 0.3 to 1 μm TiC rounded particles embedded in a steel matrix. Presented at the International Conference on Metallurgical Coatings and Thin Films, ICMCTF-92, Apr 6–10, 1992, San Diego.     

Ti- 6Al-4V/hydroxyapatite composite coatings prepared by thermal spray techniques

The poor mechanical properties of hydroxyapatite (HA) can be enhanced by forming a composite with a bioinert and mechanically strong metal alloy such as Ti-6A1-4V. Biomedical composites composed of titanium alloys and HA can offer concomitant bioactive properties as well as good mechanical strength and toughness. This paper describes an attempt to improve coating mechanical properties by forming a composite composed of HA and Ti-6A1-4V. Several compositions (20, 33, and 80 wt % HA) were prepared. Subsequent examination of the plasma-sprayed coatings revealed alternating HA-rich and titanium-rich lamella microstructures. The HA-rich regions appeared porous as a result of poor interparticle adhesion, with the 80 wt% HA coatings having the highest porosity. Mechanical property analysis showed the 20 wt% HA coating to have the highest storage modulus (∼60 GPa). This coating also had the highest bond strength (≥20 MPa max). The coatings tended to exhibit increased bond strength at thicknesses less than or equal to 60 μm. The excellent bond strength of the Ti-6A1-4V/HA composite is caused by the superior interfacial bond between the Ti-6Al-4V-rich splats and the substrate. The encouraging development of this composite raises the possibility of its use as a bond coat for plasma-sprayed HA on titanium-alloy implants.     

Microstructures and environmental assessment of metallic NiCrBSi coatings manufactured via hybrid plasma spray process

The alternative coatings to electrodeposited hard chromium plating are studied nowadays, because of the chemical composition of the baths containing Cr(VI), forbidden by several European regulations. Thermal spraying is already used in industry, but the deposited coatings still need improvements for reasons of porosity and microstructures. In this study, atmospheric plasma spraying and in situ laser irradiation by diode laser processes were combined to modify the structural characteristics of NiCrBSi coatings. The microstructure evolution was studied, with the analysis of chemical composition using energy-dispersive spectroscopy and X-ray diffraction. Results show that in situ laser remelting induces the growth of a dendritic structure which strongly decreases the porosity of as-sprayed coatings and no phase transition after laser treatment. The adopted configuration drives to the achievement of coatings without solidification cracking, one of the major defects that can occur during the solidification of metallic alloys. Furthermore, to evaluate the environmental impacts of coatings in comparison with other conventional treatments developed to melt NiCrBSi layers, a Life Cycle Assessment was carried out. The ecodesign of surface coatings has not been reported in detail in the current literature, and nowadays, life cycle analysis is an important consideration for the thermal spray community. The good environmental assessment of the hybrid process is demonstrated in this paper.     

TiC-Fe coatings prepared by flame spray synthesis process

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Microstructures and mechanical properties of AZ91D/0Cr19Ni9 bimetal composite prepared by liquid-solid compound casting

The liquid-solid compound casting technology was used to produce the AZ91D/0Cr19Ni9 bimetal composite without and with hot dipping aluminium, respectively. The influences of Al coating on microstructures and mechanical properties of AZ91D/0Cr19Ni9 interface were investigated. The results showed that the mechanical bonding was obtained between AZ91D and bare steel 0Cr19Ni9 where a gap existed at the interface; the metallurgical bonding was formed between AZ91D and Al-coated 0Cr19Ni9, which could be divided into two different intermetallic layers: layer I was mainly composed of α-Mg+β-Mg₁₇Al₁₂ eutectic structure and a small amount of MgAl₂O₄, and layer II mainly comprised of Fe₂Al₅ intermetallic compound. Furthermore, the hardness value of interface was obviously higher than that of AZ91D matrix, and the average hardness values of layers I and II were HV 158 and HV 493, respectively. The shear strength of AZ91D/Al-coated 0Cr19Ni9 interface was higher than that of AZ91D/bare 0Cr19Ni9 interface, which confirmed that Al coating could improve the adhesive strength between AZ91D and 0Cr19Ni9 during liquid-solid compound casting process.     

镀液成分对等离子电沉积镍镀层的影响

通过对镀镍液成分的改变、SEM观察、称重测量和硬度对比等方法确立了在等离子电沉积作用下,主盐和添加剂的种类及含量对镀层的结构、生长速度、表面硬度的影响规律。结果表明,以NiSO4为主盐的镀液,其含量不可过高,在100 g/L为宜,含量过高会导致表面结构疏松,镀层硬度下降;以NiCl2为主盐的镀液主盐含量可维持较大值在150～200 g/L,镀速和镀层硬度随主盐含量增加而增加;以C6H5O7Na3为添加剂的镀液,随C6H5O7Na3的含量增加镀层可逐渐变得致密,镀速先增加后减少,硬度则逐渐得到提升;以C12H25SO4Na为添加剂的镀液,随C12H25SO4Na含量的增加,镀层的生长速度变化不大,硬度却有逐步缓慢下降的趋势。     

Microstructure and properties of Al2O3-ZrO2-TiO2 composite coatings prepared by plasma spraying

Al2O3-ZrO2-TiO2 coatings were successfully prepared by plasma spraying Al2O3-ZrO2 composite powders with and without TiO2 addition.The effects of TiO2 on the ph...     

基于实时测量的等离子喷焊熔池温度对焊层组织性能的影响

等离子喷焊过程中熔池温度波动大,目前主要存在依赖人工干预、自动化程度低等问题,喷焊层质量受到很大影响。因此,喷焊过程熔池温度的实时控制是等离子喷焊技术发展的必然选择。为研究喷焊过程熔池温度变化对喷焊层组织性能的影响,开发实时监控技术打下基础,采用在线监测的方法,对喷焊过程熔池温度进行实时测量,分析了喷焊过程熔池温度对喷焊层宏观形貌、组织成分和显微硬度的影响。结果表明,等离子喷焊过程熔池温度控制在1400℃左右,喷焊层具有较好的组织与性能。喷焊过程熔池温度较低时,容易引起近熔合区形成氧化物夹杂;喷焊过程熔池温度过高时,容易造成喷焊层稀释率的增加。喷焊电流110 A时,前段喷焊层的显微硬度为(670±26) HV0.1,明显高于中段喷焊层的显微硬度(550±20) HV0.1;当喷焊电流为70、110和150 A时,喷焊层显微硬度呈由高到低的趋势。     

等离子喷涂法制备铁基硬质涂层的力学性能

为了在碳钢表面制备耐磨涂层,使涂层与基体的膨胀系数相近,减少涂层应力,将80％ Fe,13％P,7％C(质量分数,％)机械混合粉末进行等离子喷涂,制备铁基耐磨涂层.采用粘结剂对偶试样拉伸试验法测定涂层结合强度,采用表面显微硬度法分析涂层硬度,采用MMW-2型(高温)摩擦磨损试验机以40Cr硬质合金为对磨材料对涂层进行耐磨性试验.结果表明,涂层的结合强度平均值为29.16 MPa,显微硬度的平均值为7.889 MPa,高于陶瓷涂层硬度值,涂层的耐磨性能较好,磨损200 min后,涂层的磨损量在36 mg左右,磨损量约为对磨件的1/13,涂层磨损主要为磨粒磨损机制.