WC-Cr_3C_2-Ni超音速火焰喷涂层的激光热处理

采用光学显微镜、扫描电镜、X射线衍射物相分析和显微硬度、气孔率测定等试验手段,研究了WC-Cr_((3))C_((2))-Ni超音速火焰喷涂层在激光热处理前后的显微组织和性能。结果表明,激光热处理前后超音速火焰喷涂层中均存在WC、W_((2))C、Ni_((2))O_((3))、Cr_((3))C_((2))等相;激光热处理后涂层的组织致密,孔隙率降低,厚度减薄,显微硬度有较大幅度的提高。

超音速火焰喷涂制备WC-Cr3C2-Ni涂层工艺参数的优化

采用超音速火焰(HVOF)喷涂在Q235钢表面制备了WC-Cr3C2-Ni涂层,以喷涂距离、氧气流量、煤油流量为变量,设计了三因素三水平正交试验,并对涂层孔隙率、显微硬度和综合指标进行了评分,获得了最佳工艺参数组合。结果表明:WC-Cr3C2-Ni涂层的最佳工艺参数为氧气流量1 740scfh(49 242L·h^-1)、煤油流量7.0gph(26.495L·h^-1)、喷涂距离330mm。

铜结晶器HVAF法喷涂WC-Cr3C2-Ni的试验研究

为了提高结晶器铜板的抗磨损能力,采用空气助燃超音速火焰喷涂法(HVAF)在铜板表面喷涂WC-Cr3C2-Ni硬质合金涂层.性能测试结果表明,使用HVAF法制备的WC-Cr3C2-Ni涂层脱碳较轻,孔隙率低;具有高硬度、高耐磨性的力学性能,涂层平均显微硬度能够达到1337HV 0.3;涂层热稳定性较好,平均导热系数为292.11 W/(m·K).与目前使用的WC-17Co涂层相比,综合性能更佳.现场生产试验结果证实,WC-Cr3C2-Ni涂层的效果优于WC-17Co涂层.

Anticorrosion properties and thin film composite deposition of ZnSiC-Cr_3C_2 coating on mild steel

This work considered the influence of Cr3 C2 particle loading on microstructure and mechanical properties of Zn-SiC-Cr3 C2 nanocomposite produced via electrocodeposition are investigated. The surface nature of the nanocomposite coatings were characterized using scanning electron microscope(SEM)coupled with the energy dispersive spectrometer(EDS). Abrasive wear behaviour and hardness property of Zn-SiC-Cr3 C2 nanocomposite produced were investigated using CERT UMT-2 multi-functional tribological tester and Dura Scan hardness tester. The corrosion property was evaluated through linear polarization approach. The result showed that the coatings exhibited good stability and Cr_3 C_2 nanocomposite loading significantly improved the micro structural performance, hardness property,wear resistance as well as corrosion resistance of the coatings.

Effect of Salt Spray Corrosion on Tribological Properties of HVOF Sprayed NiCr-Cr3C2 Coating with Intermediate Layer

The objective of the present work was to determine the influence of the neutral salt spray corrosion on the wear resistance of HVOF sprayed NiCr-Cr3C2 coating with intermediate layer. Ni-Zn-Al2O3 coatings as interlayers were prepared by low pressure cold spray（LPCS） between NiCr-Cr3C2 cermet coatings to form a sandwich structure to enhance the corrosion resistance properties. The tribological properties were examined using the UMT-3 fricition and wear tester by line-contact reciprocating sliding under dry and salt spray one week corrosion. The morphology, element distribution, and phase compositions of the coating and worn sufaces were analyzed by using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction respectively. The corrosion behavior of the coating was studied by the open-circuit potential, the electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray corrosion methods. It is found that the sandwich structured coating has better corrosion resistance than the single layer coating. The results show that under dry wear conditions, the wear mechanism is abrasive and adhesive wear, whereas under salt spray corrosion conditions it becomes corrosion wear. The friction coefficient of the sandwich structured coating after salt spray corrosion is slightly lower than the dry friction coefficient, but the weight of the wear loss is lower than that under dry condition.

Thermal Shock Resistances of FeMnCr/Cr_3C_2 Coatings Deposited by Arc Spraying

Arc spraying with the cored wires was applied to deposit FeMnCr/Cr3C2 coatings on low carbon steel substrates, namely FM1, FM2 and FM3. Thermal shock resistances of the coatings were investigated to assess the influence of Cr3C2 content on thermal shock resistance. Characteristics of the coatings under thermal cycling test were studied by optical microscopy, field emission scanning electron microscope （FE-SEM） and energy dispersion spectrum （EDS）, X-ray diffraction （XRD）. The experimental results show that hardness of the coatings increases, bonding strength decreases slightly with increase of the Cr3C2 content of the coatings. As a result, FM2 coating possesses the best thermal shock resistance, attributing to its better thermal expansion matches and wettability than those of FM3 coating, less oxide rate than that of FM1 coating restraining from cracks formation and propagation in coatings.

High temperature behaviors of high velocity arc sprayed Fe-Al/Cr_3C_2 composite coatings

Fe-Al/Cr3C2 composite coatings were manufactured using high velocity arc spraying （HVAS） technology. The high temperature erosion, wear and corrosion resistance of the coatings were investigated. The coating properties such as bonding strength, porosity, hardness as well as microstructures were characterized. The results show that the coatings have relatively high heat tremble bond strength, hardness, and typical layer-shaped coatings＇ microstructures. With the rise of temperature, the coating erosion resistance increases too; the impingement angel does effects on erosion properties, and the erosion mechanism changes from ductile to brittle behaviors at 450℃. The coatings have good room temperature wear resistance and relatively good high temperature resistance. The wear mechanism of the coatings is peeling wear behavior. The coatings have excellent high temperature corrosion resistance because of the produce of oxides during corrosion.

The Hot Corrosion Performance of NiCr-Cr_3C_2 Cermet Coating to Boiler Tube

Three kinds of NiCr-Cr 3C 2 cermet coatings were designed and deposited by the subsonic velocity flame spraying, and their performances of hot corrosion performance were evaluated in comparison with 102G, 20G boiler tube steel, FeCrAl, NiCrTi, Ni50Cr and NiCrAlMoFe-Cr 3C 2 coatings, which are widely used at present for protection of boiler tubes. Meanwhile,the influence of sealer on the hot corrosion resistance of various coatings and the mechanisms of coating corrosion were explored.

Cr_3C_2-Ni-Ti_3SiC_2新型减摩复合材料的高温摩擦学行为

采用粉末冶金工艺制备一种新型Cr3C2-Ni-Ti3SiC2减摩材料,并研究Ti3SiC2添加量对其与GCr15摩擦副在400℃大气环境下摩擦学行为的影响。结果表明:在高温摩擦场的作用下,复合材料中的Ti3SiC2能够诱发形成具有良好减摩作用的摩擦氧化膜,不仅可以降低摩擦副的摩擦因数,避免摩擦因数的较大波动,而且能够显著降低摩擦系统的总磨损率,对摩擦偶件起到极好的保护作用。当Ti3SiC2含量(质量分数)分别为2.5%、5.0%、7.5%和10%时,复合材料的摩擦因数比未添加Ti3SiC2的Cr3C2-Ni金属陶瓷的摩擦因数分别下降5.3%、15.8%、26.3%和13.2%,摩擦副的总磨损率也下降了一个数量级;同时,摩擦偶件的磨损率也由3.5×10-5 mm3/(N·m)逐步下降到9.8×10-7 mm3/(N·m)。

激光熔覆Cr_3C_2-Ni复合涂层的减摩性能

以粉末化学镀法制备的Cr3C2-Ni复合粉末作为预置层,在Q235钢板表面用激光熔覆技术制备了减摩复合涂层。研究了Cr3C2-Ni涂层在干摩擦条件下的减摩性能,并对磨损形貌进行了SEM观察,对涂层的硬度进行了测试。结果表明,该涂层组织均匀致密、硬度较高;涂层的摩擦性能稳定,摩擦系数为0.44;硬质Cr3C2粒子与金属粘结相的配合能有效提高熔覆层的承载能力,减小摩擦损失。

原位自生WC-Cr_3C_2复相陶瓷增强铁基表面复合材料

采用激光熔覆协同燃烧合成表面涂层技术在铁基材料表面原位生成复相陶瓷涂层。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等方法对涂层的物相组成、显微形貌、组织成分等进行了研究,结果表明涂层主要是由WC、Cr3C2、-σFeCr和Fe2W所组成的复相体系。界面形貌特征表明涂层与基体之间为冶金结合。硬度及摩擦磨损试验表明,涂层的硬度及耐磨性能明显高于基体材料。热震实验结果显示涂层与基体具有良好的结合力。

超音速火焰喷涂WC-Cr_3C_2-M涂层性能及其在液压支架立柱上的应用研究

分别采用电镀和超音速火焰喷涂在27SiMn钢表面制备了硬铬和WC-Cr_3C_2-M涂层,测试了两种涂层的机械性能以及磨损和腐蚀性能,并将WC-Cr_3C_2-M涂层在煤矿的液压支架的立柱上井下应用。结果表明:相对于电镀硬铬涂层,采用超音速火焰喷涂工艺制备的WC-Cr_3C_2-M涂层与基体结合强度高,孔隙率低,表现出更高的硬度、耐磨和抗腐蚀性能。WC-Cr_3C_2-M涂层在井下实际工况下防护效果显著,可以代替会给环境带来严重污染的电镀硬铬,用于煤矿井下的液压支架的表面防护。

空气等离子喷涂NiCr/Cr2C3涂层的制备及抗热震性能

采用等离子喷涂技术制备了NiCr/Cr2C3涂层,并采用SEM、XRD、马弗炉和高温热膨胀仪对涂层的结构、物相和热震性能进行了表征。结果表明:等离子喷涂NiCr/Cr2C3涂层呈层状结构,涂层的主晶相为NiCr和Cr2C3相,涂层在700℃、800℃和850℃时抗热震性能良好,均满足使用要求。

Silt Erosion Characteristics of a Cr_3C_2-NiCr Coating Fabricated by High Velocity Oxy-Fuel (HVOF) Thermal Spray

A Cr3C2-NiCr coating was prepared by high velocity oxy-fuel(HVOF)thermal spray on 1Cr18Ni9Ti stainless steel.Phases and microstructures of the coating were investigated by X-ray diffraction(XRD),optical microscopy(OM)and scanning election microscopy(SEM),respectively.The cavitation erosion resistance and silt erosion resistance of the coating were evaluated using a GB/T6383-2009 standard method in two experimental conditions(fresh water and water contained fine silt),compared with the coatings hydro machine material 1Cr18Ni9Ti stainless steel.The coating shows a layered structure and has a significantly higher microhardness(11.97 GPa)than that of the 1Cr18Ni9Ti stainless steel(2.1 GPa),which results in less mass losses both in cavitation erosion and silt erosion experiment.The HVOF coating has a predominant performance in the cavitation erosion and silt erosion resistance.The higher microhardness of the coating is the main cause which results in a less mass losses in the erosion experiments.And the mass loss usually happens at the edges of the pores.

Microstructure and wear-resistant properties of NiCr–Cr_3C_2 coating with Ni45 transition layer produced by laser cladding

NiCr–Cr3C2 metal–ceramic composite coating is commonly produced on metal substrate by laser cladding to be used as wear-resistant coating under medium- or high-temperature working conditions.The coating has high hardness, generally over three times that of the substrate.In order to make the hardness increase gradually from substrate to coating surface, the nickel-based alloy Ni45 was chosen as the transition layer and Ni Cr–Cr3C2 coating was indirectly cladded on 20Cr2Ni4 A substrate.Microstructure and composition of the coating were characterized by scanning electron microscope(SEM), energy-dispersive spectroscopy(EDS) and X-ray diffraction(XRD).Microhardness of the cross section of the coating was measured.Friction and wear behavior of Ni Cr–Cr3C2coating and substrate were investigated through sliding against the Si C ball at 20, 100 and 300 °C.The morphologies of worn surfaces were analyzed by SEM and EDS.The results show that the hardness of Ni45 transition layer is between that of the substrate and Ni Cr–Cr3C2coating, which avoids hardness jump and stress concentration of the coating.Ni Cr–Cr3C2coating contains hard phases of Cr3C2 and Cr7C3which enhance the wear resistance.With thetemperature increasing, friction coefficient and wear rate of the substrate increase significantly.Compared with the substrate, Ni Cr–Cr3C2coating has lower friction coefficient and wear rate at 100 and 300 °C, which verifies the good wear resistance of NiCr–Cr3C2 coating.

Microstructure and Tribological Performances of 25NiCr-Cr_3C_2 Coatings Prepared by Laser-Hybrid Plasma Spraying Technology

The 25NiCr-Cr3C2 coatings are deposited on 38CrMoAl substrate by air plasma spraying and laser-hybrid plasma spraying (LHPS) technologies,the coatings' microstructures and tribological performances were studied using an optical microscope,a scanning electron microscope,an X-ray diffraction,and an SRV high-temperature friction and wear tester.At the same time,the coating's bonding strength,microhardness are tested and analyzed.The test results indicate that the LHPS 25NiCr-Cr3C2 coating achieves metallurgy bonding and has higher bonding strength and higher microhardness than the air plasma spraying coating for the addition of the laser power.The laser power makes the 25NiCr-Cr3C2 powders melt more sufficiently and has good fluidity and uniformity and therefore the LHPS 25NiCr-Cr3C2 coating's microstructures become more compact and there are no big cracks and cavities in it.For the above changes,the LHPS 25NiCr-Cr3C2 coating has more excellent anti-high temperature abrasion performance and its friction coefficient is low and very stable,its main failure mechanism is a good combination of mild scratching and plastic deformation.

Enhanced wetting and properties of carbon/carbon-Cu composites with Cr_3C_2 coatings by Cr-solution immersion method

A facile ammonium-dichromate solution immersion method was introduced to synthesize the copperwettable Cr3C2 coating on and inside the carbon-carbon （C/C） preform. The formation mechanism and the microstructures of the Cr3C2 coatings were studied. The contact angle between molten copper and the C/C decreased from 140°to 60°, demonstrating the significant improvement in the wettability. The Cr3C2- coated C/C-Cu composite with only 4.2% porosity and 3.69 gcm^-3 density was manufactured through copper infiltration. As a result, the thermal and electrical conductivity of the modified C/C-Cu increased significantly due to the infiltrated copper. Also the mechanical properties of the composites including both the flexural and compressive strengths were enhanced by over 100%. The modified C/C-Cu composite exhibited lower friction coefficients and wear rates for different load levels than those of the commercial C/Cu composite. These results demonstrate the potential of the modified C/C-Cu material for use in electrical contacts.

Microstructure evolution of nanostructured ferritic alloy with and without Cr3C2c oated SiC at high temperatures

This work focuses on fundamental understanding of microstructure evolution of nanostructured ferritic alloy(NFA) and 25 vol.% Cr3C2 coated Si C(Cr3C2@Si C)-NFA composite during spark plasma sintering at950°C and the following thermal treatment at 1000°C. A unique bi-phase microstructure with distinct Cr-rich and Si-rich phases has been observed for the 25 vol.% Cr3C2@Si C-NFA composite, while for the NFA sample, the traditional large grain microstructure remains. Grain sizes are significantly smaller for the25 vol.% Cr3C2@Si C-NFA composite compared to those for the pure NFA, which can be attributed to the presence of grain boundary phases in the composite sample. During the thermal treatment, microstructure features can be directly correlated with the dissolution kinetics and phase diagrams calculated using Thermo-Calc/DICTRA/PRISMA~?.

Wear-resistant coating spraying technique for wear-proofing cover of coke dry quenching furnace

During the operation of a coke dry quenching system of coking plant, wear-proofing cover of the boiler was seriously eroded, and even the ceiling tube of the boiler was worn and torn. Thus, attentions were paid to the research, development and application of the wear-resistant coating spraying technique for wear-proofing cover of the coke dry quenching furnace. The Cr3C2–NiCr coatings for wear-proofing cover were fabricated via supersonic arc spraying process, and the residual coating of wear-proofing cover would be sampled for being analyzed after two years. The coating presents a dense microstructure with few pores and micro-cracks (the porosity is 4.65%). After thermal spraying of the wear-proofing cover, the hardness and the wear resistance of the surface are improved. The remaining coating is continuous and compact, with an average thickness of about 147μm. Transverse micro-cracks parallel to the spreading direction of the coating surface are displayed on different areas of the coating, which demonstrates its serious erosion wear effect. The main chemical component of white zone is Fe–18Cr–Ni. The Cr level of light gray phase is about 77.57 wt.% and the O level is 22.43 wt.%. And the main chemical components of dark gray phase are C, O, Al, Si and Ca. X-ray diffraction patterns were adopted to implement phase analysis on the surface of coating sample, which indicated that the coating was composed of a large amount of Cr3O2 and a small amount of metal Cr.

超音速等离子喷涂技术在活塞裙表面热喷涂材料的研究

活塞裙与气缸套直接接触,是活塞的重要组成部件,承受着气体力、侧压力,热负荷等。极易产生摩擦和磨损,因此需要其有着优异的高温稳定性、耐腐蚀性、坚韧性、耐磨性和抗咬合性。通过超音速等离子技术在球墨铸铁活塞裙上喷涂WC-Co涂层和Cr3C2-Ni Cr涂层,用SEM分析了粉末的表面形貌,对涂层的表面和界面形貌及相结构进行了分析。通过对这两种涂层进行孔隙率、结合强度、显微硬度、耐磨性能、耐腐蚀性能对比测试实验,以达到使活塞裙外壁的综合性能得到大的提升的目的。