Wear resistance of Zr/WC composite coatings on Cr12MoV steel surface by electric spark deposition

Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.

Preparation and properties of flame-sprayed Mo-FeB-Fe cermet coatings

The powders of Mo2FeB2 cermet were prepared with Mo powders, Fe-B alloy powders and Fe powders as raw materials. Mo2FeB2 cermet coatings were prepared on Q235 steel by reactive thermal spraying （RTS） method and heated at 1 000 ℃ in vacuum oven of 1 kPa for 5 h. The properties of coatings were investigated. The results indicate that Fe2B appears after milling for 15 h in the powder at room temperature, a part of ternary borides （Mo2FeB2） are generated in powder sintered at 900 ℃. The coatings are composed of the major phases Mo2FeB2 and a-Fe, a little of Fe203, FeO and some pores. The bonding strength between the substrate and the ceramic coating is 32.73 MPa, the thermal-shock times is about 43 and the wear resistance is enhanced by approximately 5.28 times compared with that of the substrate, respectively. The comprehensive properties of Mo2FeB2 cermet coatings can be imoroved further after vacuum heat-treatment at 1 000 ℃ for 5 h.

Mo添加对WC-Ni硬质合金微结构及性能的影响

采用X射线衍射(XRD)、扫描电子显微镜(SEM)和性能检测等方法研究了不同Mo添加量对WC-Ni-Mo硬质合金的WC粒度、硬度、摩擦磨损和耐腐蚀性能的影响。结果表明:在研究的成分范围内(w(Mo)=1.5%~2.0%),WC的平均晶粒尺寸基本不随Mo添加量的变化而变化;随Mo添加量的增加,WC-Ni-Mo硬质合金的硬度略微有所下降,而摩擦磨损性能得到提升。Mo质量分数为2%的WC-Ni-Mo硬质合金在酸性溶液中的耐腐蚀能力要高于Mo质量分数为1.5%的合金,并且具有更好的电化学稳定性。总体来看,WC-8.0%Ni-2.0%Mo合金的综合性能优于WC-8.5%Ni-1.5%Mo硬质合金。

Mo对激光熔覆WC/Ni35涂层组织与性能的影响

针对高WC含量的WC/Ni35熔覆层容易出现裂纹的问题,在WC/Ni35熔覆层中添加2、5和8 mass%Mo元素,研究Mo对WC/Ni35熔覆层组织与性能的影响。结果表明:随着Mo元素含量的增加,WC/Ni35熔覆层组织更加致密细小,柱状晶减少,等轴晶增加。添加2和5 mass%Mo元素的熔覆层中,Ni _(17)W_(3)、Cr_(4)Ni_(15)W等新的硬质相数量增多,导致熔覆层平均硬度增大;添加8 mass%Mo元素的熔覆层中,物相较多以含Mo的韧性相存在,其平均硬度和添加5 mass%Mo元素的熔覆层持平。Mo元素含量增加到5 mass%时,熔覆层中产生新的W的化合物,减少W元素的偏析现象,同时Cr元素对钝化膜的修复作用,使熔覆层耐腐蚀性提高;添加8 mass%Mo元素的熔覆层由于Cr的析出导致出现贫Cr区,熔覆层的耐腐蚀性降低。添加8 mass%Mo元素的熔覆层没有产生裂纹。在高WC含量的WC/Ni35熔覆层中添加8 mass%Mo元素,可以获得无裂纹、组织致密的熔覆层,其硬度提高,耐腐蚀性略有降低。

Performance of plasma-sprayed CuNiIn coatings and Mo coatings subjected to fretting fatigue

During atmospheric plasma spraying,a cooling process usually plays an important role in the coating quality,especially for the oxidation containment of metallic coatings.CuNiIn and Mo coatings were prepared using atmospheric plasma spraying with different cooling processes.The obtained coatings were characterized in terms of microstructure,microhardness and tensile strengths.The relation between the coating microstructure and their fretting fatigue behavior was emphasized.The results show that the sensitivity of Mo coatings to the cooling process is lower than CuNiIn coatings.The resistance to fretting fatigue is determined by the coating microhardness,correlated with the contents of oxides and pores.The fretting wear mechanisms of both the coatings are galling,third body abrasive wear and material transfer.

Thermal sprayed WC-Co coatings and their mechanical properties

HVOF thermal spraying tests were carried out for thermal spraying the coatings with two kinds of cermet powders,which are microstructured Sulzer Metco Diamalloy 2004 WC-12%Co powders and nanostructured WC-12%Co powders.The microstructures of the as-prepared WC-12%Co coatings were then characterized by using XRD analyzer and SEM.The mechanical properties of the two coatings were evaluated by microhardness test,bend test,cup test,tensile test and abrasive wear test.The results showed that the mechanical properties of WC-12%Co coatings sprayed with nanostructured WC-12%Co powder is higher than that of coatings sprayed with microstructured WC-12%Co powders,and the reasons were discussed.

Influence of Heat Treatment on Microstructure and Sliding Wear Behavior of Fe-Al/WC Composite Coatings

An experimental study has been carried out to investigate the influence of heat treatment at 300 ℃,450 ℃,550 ℃,650 ℃ and 800 ℃ on the microstructure and sliding wear behavior of Fe Al/WC intermetallic composite coatings produced by high velocity arc spraying (HVAS) and cored wires. The result shows, the main phases in both as sprayed and heat treated Fe Al/WC composite coatings are iron aluminide intermetallics (Fe 3Al+FeAl) and α as well as a little oxide (Al 2O 3) and carbides (WC, W 2C, Fe 2W 2C and Fe 6W 6C). After heat treated at 450-650 ℃, dispersion strengthening of Fe 2W 2C and Fe 6W 6C will lead to a rise in microhardness of the coatings. The microhardness is likely to be the most important factor which influences the sliding wear behavior of the coatings. Increasing the microhardness through heat treatment will improve the sliding wear resistance of the Fe Al/WC composite coatings.

Ni-WS_(2)/MoS_(2)包覆WC-12Ni粉体对HVOF涂层摩擦磨损性能的影响

以化学共沉积Ni-WS_(2)/MoS_(2)包覆WC-12Ni粉体为原料,在17-4PH不锈钢基体上制备了超音速火焰喷涂(HVOF)涂层。采用场发射扫描电子显微镜对涂层组织结构进行表征,分别通过测定涂层的显微硬度、摩擦系数和磨损率,并结合粉体特征及涂层的孔隙结构分析来评价涂层摩擦学性能。实验结果表明,通过化学共沉积包覆喷涂粉体引入固体润滑剂,不仅能保证喷涂粉体的流动性,还能实现较均匀固体润滑剂掺杂,显著降低涂层孔隙率、提高致密化程度,获得低摩擦系数、低磨损率以及提高的涂层硬度和耐磨性。其中,由于WS_(2)与WC硬质合金有更好的成分相容性,WC-Ni-WS_(2)涂层的减摩耐磨性能要优于WC-Ni-MoS_(2)涂层。

Tribological Behavior of Thermally Sprayed WC Coatings under Water Lubrication

Thermally sprayed coatings have been used in various fields of industry for enhancing surface characteristics of materials and extending their service life. The contact surface of some mechanical equipment such as the fine pulverization equipment which is used in the woody biomass production process is required to have wear resistance in the water environment. Thermally sprayed coatings would be a good candidate to improve surface wear resistance under water lubrication. The objective of this study was to evaluate the tribological performance of thermally sprayed coatings under water lubrication. Thermally sprayed coatings which were classified into WC, WB and Ni spraying of three categories were compared with water-lubricated sliding test at a sliding velocity of 0.02 m/s and mean pressure of p0 = 10 MPa with a ring-on-disk apparatus. Thermally sprayed coatings showed comparatively high friction coefficient and well wear resistance under water lubrication. WC contained coatings showed better wear resistance than WB and Ni coatings. Thermally sprayed coatings showed obviously different mechanical properties and tribological behaviors, and the effect of wettability and hardness on tribological characteristics was discussed under water lubrication. Friction coefficient increased as the surface contact angle of thermally sprayed coatings increased. The wear rate decreased as the surface hardness of thermally sprayed coatings increased. Wear resistance of thermally sprayed coatings was excellent under water lubrication. WC contained coatings showed lower wear rate than WB and Ni coatings. WC-14CoCr coating showed the lowest wear rate.

Microstructure and Properties Characterization of WC-Co-Cr Thermal Spray Coatings

WC-Co-Cr coatings are widely employed due to their improved wear resistance and mechanical properties, however, the properties and performance of these coatings are compromised by the processing parameters of each spraying technique. Therefore, this study is aimed to evaluate and determine the effect of the deposition parameters on the properties and microstructural characteristics of WC-Co-Cr coatings using a more economical thermal spray technique. In particular, the influence of flame spray parameters on the microstructure, crystal structure, hardness, and sliding wear resistance of WC- Co-Cr coatings was examined. Two parameters were considered: Type of flame (reducing, neutral and oxidizing), and the spray torch nozzle exit area. Results indicated that WC particles undergo considerable degree of decarburization and dissolution during spraying, showing substantial amounts of W2C, W, and Co3W3C, for all the considered conditions. However, the extent of phase transformation depended largely on the flame chemistry. The microstructure of the coatings was mainly affected by the spray nozzle. Regarding the sliding wear behavior, the coatings with uniform distribution of hard particles provided the best wear resistance. The decomposition of WC into W2C phase seems to have meaningless significance in the mass loss, nevertheless, the WC phase transformation to metallic tungsten and η-phase (Co3W3C) produce higher wear rates due to deficiency of carbide particles and embrittlement of the binder phase which induces cracking and delamination of the splats.

Formation and Oxidation Resistance of Silicide Coatings for Mo and Mo-Based Alloys

The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gas- phase deposition method. has been studied by examining the microstructure of coatings and the relationship between coating thickness and process parameters. It was shown that the growth of coatings was diffusion-controlled, the diffusion of silicon to be coated into Mo or Mo-base alloys was mainly responsible for the formation of silicide. The relationship between initial silicide thickness and oxidation resistance was also investigated, and the equation of service life of the coatings at high temperature in air is presented.

Oxidation behavior of Fe40Al-xWC composite coatings obtained by high-velocity oxygen fuel thermal spray

The Fe40Al-xWC(x=0,10,12,15)coatings with dense structure were successfully deposited by high-velocity oxygen fuel (HVOF)spraying of a mixture of Fe,Al and WC powders.The objective of the present work is to provide insight into the oxidation behavior of the as-deposited coatings at 650℃under 0.1 MPa flowing pure O2.The present results show differences in the oxidation behavior of Fe40Al coating and Fe40Al-xWC composite coatings.The irregular Fe2O3 layer is seen on the top surface of the composite coatings.Fe40Al coating and Fe40Al-15WC composite coating both suffer a catastrophic corrosion due to the formation of a porous structure during 24 h of oxidation.However,Fe40Al-10WC and Fe40Al-12WC composite coatings show a good oxidation resistance behavior due to their dense structure.

Effect of Substrate Type and Temperature on the Tribological Properties of MoS_x Coatings

MoS coatings were prepared by means of bipolar-pulsed DC magnetron sputtering on different substrate type at various temperature. The structure and fretting behavior of MoS, coatings have been determined respectively by XRD and fretting tester in air of 10% to 90% RH and under the load of 1 to 10 N. With increasing substrate temperature, the edge orientation evolves in the MoSx coating, and the relative content of edge-to-basal orientation becomes large. The tribological performance of coatings gets deteriorated. Compared with MoS, coatings on TiN/H13, CrN/H13 and MoS /Ti multilayer, MoS coating on H13 substrate has a lower load bearing capacity, and worn away easily under higher normal load 5N or ION and in air of 90% RH during the fretting process. The friction and wear properties of MoS, coatings on TiN/H13 and CrN/H13 (dual-layer) are slight better than that of MoS, /Ti multilayer under the normal load tested and in air of<10%to90%RH.

Tribological Performance of MoS_2-based Coatings after Deposition and Storage in Humid Air

MoS 2-based composite coatings were deposited with the nano-compound unbalanced plasma plating technique. The effects of processing parameters and working environments on the tribological properties of the coatings were examined by the drilling experiments and XPS. The distances between substrate and Ti target, Ti content and deposition pressure were varied in order to determine the optimum conditions for producing lubricious, long-lasting MoS 2-based coatings. It is found that the tribological performance of TiN-MoS 2 coating decreases rapidly in humid air but the humid-resistant property of TiN-MoS 2/Ti coating improves evidently.It is indicated that the humid-resistantance property and the abrasion durability of MoS 2-based coatings can be enhanced markedly by adding Ti with a certain contents.

Microstructure and interface thermal stability of C/Mo double-coated SiC fiber reinforced γ-TiAl matrix composites

C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.

WC和Mo_2C添加对Ti(C,N)基金属陶瓷切削性能的影响

传统的Ti(C,N)基金属陶瓷刀具材料广泛采用Mo2C来改善粘结相对硬质相的润湿性,近年来Mo的价格不断上涨,寻找低成本金属代替Mo已成为Ti(C,N)基金属陶瓷的发展趋势。为了探讨WC代替Mo2C添加的可行性及其效果,研究了WC和Mo2C添加对Ti(C,N)基金属陶瓷切削性能的影响,采用电子扫描显微镜(SEM)观察刀具的磨损形貌,通过能谱分析(EDS)分析磨损表面的元素分布,并对刀具的主要磨损机理进行分析。实验结果表明,添加WC的金属陶瓷的切削长度和添加Mo2C的相当,将原始WC粉末粒度细化后,不仅切削长度显著增加,切屑也由带状缠乱型变为螺旋型,并且大大减少积屑瘤的形成,有利于切削的进行。切削磨损机理主要为扩散磨损和氧化磨损,伴有轻微的磨粒磨损。

WC增强Mo_2FeB_2基金属陶瓷的组织与性能研究

在三元硼化物Mo2FeB2基金属陶瓷的基础上添加不同量的WC进行真空液相烧结,并对烧成的试样进行表征。结果表明,添加WC颗粒不影响生成三元硼化物Mo2FeB2的原位液相反应过程,其可作为Mo2FeB2颗粒的形核中心,进一步促进材料烧结致密化,且WC颗粒与Mo2FeB2硬质颗粒形成结合良好的双硬质相,弥散分布在Fe基粘结相中,有效地增强了Mo2FeB2基金属陶瓷硬度及耐磨损性能。当WC添加量为20%(质量分数)时,材料硬度最高,达到HRA87.9,提高了7.2%,在砂轮对磨试验条件下其耐磨性最好,提高了10倍。

Mo/WC中高温太阳能选择性吸收涂层的优化设计及性能评价

目的在保证WC基热喷涂涂层在高温自然环境中性能稳定的情况下,研究改进其选择性吸收性能。方法通过Mo来提高WC基涂层的选择性吸收性能,重点评价优化的Mo/WC涂层显微结构、选择性吸收性能和耐候性能等。结果金属粒子Mo填充在WC陶瓷中的结构特征,使涂层相结构和高温性能较为稳定,吸收率高达0.836~0.890,但发射率也上升至0.493~0.594,选择性吸收性能不佳。经Al_2O_3-SnO_2减反层处理后,Mo/WC涂层的吸收率仍可稳定在0.77~0.78,而发射率随着热处理温度的上升呈现先降低后升高的趋势。500℃热处理条件下,吸收效果达到最佳,此时发射率最小,低至0.168。Mo/WC涂层抗热震及耐盐雾腐蚀性能也有效提高。结论 Mo/WC涂层选择性吸收性能及自然环境适应性得到有效提高,并兼具了生产成本和施工便利性等优势,有利于太阳能清洁能源利用的发展。

爆炸喷涂WC-Co/MoS_2-Ni多层复合自润滑涂层的摩擦学行为

采用爆炸喷涂技术研制WC-Co/MoS_2-Ni多层复合自润滑涂层,系统研究涂层的微观结构、元素分布、结合强度和摩擦磨损性能。结果表明:在高温爆炸喷涂过程中,少量MoS_2发生氧化分解,生成SO_2气体,残留在涂层内的SO_2气体可使局部形成微小孔洞。在摩擦测试中,WC-Co涂层在预磨阶段摩擦因数迅速上升,进入稳定阶段后,摩擦因数缓慢增加;而多层复合涂层的摩擦因数在经历预磨阶段迅速上升后,很快进入稳定阶段,直至表层WC-Co涂层被磨穿后,摩擦因数开始逐渐下降。添加自润滑涂层MoS_2-Ni后,WC-Co涂层的内聚结合强度略有下降,但减摩效果显著,摩擦因数下降了约40%,耐磨性能略有提升。

结晶器CuNiCoBe合金表面等离子喷涂WC-Co及Mo/WC-Co复合涂层的性能

采用等离子喷涂方法在CuNiCoBe合金表面制备了单一WC-Co涂层和Mo/WC-Co复合涂层.利用扫描电镜(SEM)对涂层的微观形貌进行观察分析,并对涂层的结合强度、抗热震性能以及涂层的摩擦性能分别进行了研究.结果表明:涂层为典型的层叠结构,涂层与基体、涂层与涂层之间结合良好;复合涂层与基体间的结合强度及涂层的抗热震性能均优于单一涂层;WC-Co涂层的平均摩擦系数随着温度的升高而下降.