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.

调制周期对AlCrSiN/AlCrMoSiN多层膜微结构和性能的影响

目的通过优化AlCrSiN/AlCrMoSiN多层复合涂层的调制周期,提升涂层的力学性能和摩擦学性能。方法采用高功率脉冲磁控溅射与脉冲直流磁控溅射复合技术,固定调制比为5∶1,制备具有不同调制周期的AlCrSiN/AlCrMoSiN多层复合涂层。利用XRD和SEM分析涂层物相组成,观察其微观形貌;借助纳米压痕仪、划痕仪、高温摩擦试验机及轮廓仪测试涂层的硬度、弹性模量、临界载荷,以及摩擦磨损性能。结果掺杂Mo元素后,AlCrMoSiN层生成了大量的非晶相,并观察到沿AlN(111)晶面共格外延生长。AlCrSiN/AlCrMoSiN多层复合涂层表面颗粒随着调制周期的增大逐渐变小,整体呈“花椰菜”状,且致密、无缺陷。随着调制周期的增大,硬度、H/E和H^(3)/E^(*2)呈先升高后降低的趋势;涂层的平均摩擦因数呈先降低后升高的趋势。当调制周期为145 nm(AlCrSiN层厚度约为120 nm,AlCrMoSiN层厚度约为25 nm)时,多层涂层中层间界面清晰,涂层的硬度最高,约为24.9GPa,摩擦因数和磨损率均最低,分别为0.57、1.46×10^(-6)mm^(3)/(N·m),临界载荷为75.8N。结论多层复合涂层的调制周期对其结构和性能具有重要影响,当调制周期为145nm时,AlCrSiN/AlCrMoSiN多层复合涂层具有最佳的综合性能。

Mo含量对AlCrMoSiN涂层微观结构和性能的影响

目的解决AlCrSiN涂层在高速干切削工况下耐磨性不足,其服役寿命大幅降低的难题。方法采用高功率脉冲磁控溅射和脉冲直流磁控溅射复合技术,对AlCrMoSiN涂层中的Mo含量进行优化,研制一系列具有不同Mo含量的AlCrMoSiN涂层,通过调节CrMo靶溅射功率,改变涂层中的Mo含量。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和高分辨透射电子显微镜(HRTEM)、纳米压痕仪、纳米划痕仪、高温摩擦磨损试验机等检测设备对涂层微观形貌、物相组成、力学性能、摩擦学行为进行表征。结果随Mo含量的增加,AlCrMoSiN涂层的晶粒尺寸增大,涂层厚度增加;XRD衍射峰向大角度偏移,并在(111)和(200)晶面上择优取向明显,涂层中逐渐形成以fcc-(Al,Cr,Mo)N固溶相为主的结构。Mo元素的掺杂使涂层内部出现晶格畸变现象,在一定程度上增强了涂层的韧性。当涂层中Mo的原子数分数达到21.3%时,涂层的特征值H/E和临界载荷达到最高,分别为0.059和67.62 N,涂层的摩擦因数为0.54,磨损率最低为7.97×10^(–4)μm^(3)/(N·μm)。结论Mo元素的掺杂提高了AlCrMoSiN涂层的结晶度,当Mo的原子数分数为21.3%时,涂层的耐磨损性能最佳。

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.

Preparation and Microstructure of a Si-Mo Fused Slurry Coating on Carbon/Carbon Composites for Oxidation Protection

A coating of composition Si-40Mo (wt pct) was prepared by fused slurry coating method on the two-dimensional carbon/carbon (2D-C/C) composite to improve oxidation resistance. In the procedure of the fabrication, pure St slurry inner layer in the pre-coating was necessary to apply because of infiltration of liquid Si into the substrate during the sintering. The coating consists of Si continuous phase and MoSi2 particles. In addition, the infiltration of Si into the substrate and the SiC reaction layer between the coating and the C/C composite were observed. Oxidation behavior of coated and uncoated C/C composites was studied in cyclic mode. The oxidation resistance and the thermal shock resistance of the Si-Mo fused slurry coating were quite excellent at 1370℃.

Characteristics of electrodeposited RE-Ni-W-B-B_4C-MoS_2 composite coating

The high temperature oxidation resistance of RE Ni W B B 4C MoS 2 composite coating, the effects of electrodeposition conditions on the morphologies of the coating and the effect of heat treatment temperature on its hardness, abrasion resistance and phase structure were investigated by using scanning electron microscope(SEM), X ray diffractometer, microhardness tester and abrasion machine. The results show that the oxidation degree of RE Ni W B B 4C MoS 2 composite coating is small when the temperature is lower than 700 ℃, but it increases sharply when the temperature is higher than 700 ℃. The hardness of RE Ni W B B 4C MoS 2 composite coating increases with increasing heat treatment temperature, it comes up to the maximum value at 400 ℃,but it decreases gradually if the temperature rises continuously. The most favourable abrasion resistance was attained after RE Ni W B B 4C MoS 2 composite coating being heat treated at 400 ℃. Without heat treating, it is mainly amorphous and partially crystallized, but wholly crystallized after being heat treated at 500 ℃. RE in the composite coating is in the form of CeO 2 and additions of CeO 2 and B 4C can enhance the thermostability of RE Ni W B B 4C MoS 2 composite coating.

Si-Al COATING ON PURE MOLYBDENUM SUBSTRATE AND ITS CYCLIC OXIDATION BEHAVIOR

The halide-activated pack cementation method is utilized to codeposit aluminum and silicon on Mo substrate. Emphasis is placed on the microstructure and elevated-temperature oxidation resistance of coatings. The results show that hexagonal Mo(Si, Al)2 as a main phase and a little amount of the lower disilicide Mo5Si3 was formed on Mo substrate through the halide-activated pack cementation method. The resultant Si-Al coating on Mo substrate exhibits excellent cyclic oxidation resistance. The excellent cyclic oxidation resistance of the coatings is attributed to the formation of alumina on the coatings during the oxidation.

Fabrication of Ti-Ni-Mo-Si composite coating by reactive braze coating process

Ti-Ni-Mo-Si composite coating was fabricated on mild steel by reactive braze coating process with Ti61. 9Ni24. 6Si4. 411409.1 （ wt. % ） powders as the raw materials. Microstr^cture of the coating was characterized by optical microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy and micro-hardness tester. Results indicate that the Ti-Ni-Mo-Si composite coating is metallurgically bonded to the mild steel substrate and has high hardness. The microstructure of the coating consists of the reinforcement of Ti5 Si3 and Mo9 Ti4 particles and the matrix of eutectic NiTi2. Due to the poor wettability of NiTi2 liquid at low temperature, TisSi3 and Mo9 Ti4 do not uniformly distribute in the NiTi2 matrix.

Effect of temperature on microstructure of molybdenum diffusion coating on titanium substrate

The halide-activated pack cementation process was used to form molybdenum diffusion coating on titanium substrate. The morphology, structure, elements diffusion distribution and microhardness of the coatings formed at different diffusion temperatures were studied. The results indicate that the coating is made up of deposition layer and diffusion layer, and the surface roughness of specimens is increased after diffusion. In the diffusion layer, the major phases are Mo and β-Ti phase with addition of α′-Ti phase and α″-Ti phase. And the phase composition of Mo→β→α″→α′ is formed for different Mo contents in the diffusion layer from outside to inside. The diffusion of Ti element is very obvious as well as Mo element. With increasing the diffusion temperature, the thickness of diffusion layer is increased rapidly, and the microhardness is changed more smoothly with diffusion depth, which shows the same distribution rules as the Mo content.

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.

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.

MICROSTRUCTURE AND CORROSION RESISTANCE OF LASER SURFACE ALLOYING PLASMA SPRAYED Cr-Mo COATING

The precipitation of χ-phase,σ-phase and carbides may be restrained or eliminated by laser melting the plasma sprayed Cr-Mo alloy coating,in which austenite of abundant block usual- ly occurred on medium carbon low alloying steels.The corrosion resistance of this coating to 0.5mol/L H_2SO_4 was examined to be superior to that of 18-8 stainless steel.The laser al- loying Cr-Mo coating also has excellent resistance to pitting corrosion,and no pitting ap- peared even it immersed in a medium containing Cl^- ions.

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.

大气等离子喷涂NiCoCrAlYTa-Cr_(2)O_(3)-Cu-Mo高温耐磨涂层组织和性能

为了探究工艺参数对NiCoCrAlYTa-Cr_(2)O_(3)-Cu-Mo高温耐磨涂层性能的影响规律,基于正交实验,采用大气等离子喷涂(atmospheric plasma spray,APS)工艺制备NiCoCrAlYTa-Cr_(2)O_(3)-Cu-Mo涂层,应用极差分析法研究工艺参数对NiCoCrAlYTa-Cr_(2)O_(3)-Cu-Mo涂层显微组织、硬度和结合强度性能影响的主次关系,完成喷涂工艺参数优化。优化后的工艺参数为氩气流量为50 L/min,氢气流量为12 L/min,电流为500 A,喷涂距离为100 mm。结果表明:采用优化后的工艺参数喷涂的NiCoCrAlYTa-Cr_(2)O_(3)-Cu-Mo涂层显微组织均匀致密,涂层孔隙率小于1%,结合强度平均值为70.7 MPa,硬度平均值为543.7HV,900℃温度下50~100 h平均氧化速率为0.07302 g/(m^(2)·h),达到完全抗氧化级别,在800℃表现出良好的摩擦磨损性能,平均摩擦因数为0.248,磨损率为2.12×10^(-6) mm^(3)/(N·m)。

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.

调制比对AlCrSiN/AlCrMoSiN多层复合涂层结构的影响及涂层刀具的切削性能

为解决硬质合金刀具切削淬硬钢时面临易磨损、寿命短的难题,在刀具表面涂覆硬度高、耐磨损的防护涂层是一种经济实用的方法。利用高功率脉冲磁控溅射与脉冲直流磁控溅射复合技术制备了不同调制比的AlCrSiN/AlCrMoSiN多层复合涂层,利用扫描电镜、纳米压痕仪、白光干涉仪等对多层膜的微观结构、力学性能以及涂层刀具的切削性能进行表征和分析。研究表明,当调制比为3∶1时,多层膜择优生长取向由(111)晶面转为(200)晶面,多层膜的表面致密度得到改善,层状结构明显,晶粒得到细化。此时,涂层硬度达25.7 GPa,临界载荷为79.6 N,耐磨性最强,磨损率为0.74×10^(-6)mm^(3)/(N·m),摩擦系数最低约0.45。将后刀面磨损带宽度0.3 mm作为磨钝标准,干切削淬火C1045中碳钢,AlCrSiN/AlCrMoSiN多层复合涂层刀具的寿命比AlCrSiN涂层刀具寿命提高1.2倍,比无涂层刀具寿命提高3.2倍。切削过程中多层复合涂层内部分Mo元素被氧化成层状MoO3,起到润滑作用,有效降低了切削力和摩擦产生的切削热,延长了刀具使用寿命。无涂层刀具、AlCrSiN涂层刀具、AlCrSiN/AlCrMoSiN多层复合涂层刀具连续切削25 min后,切屑颜色越来越浅,切削温度越来越低。经观察与计算,AlCrSiN/AlCrMoSiN多层复合涂层刀具所产生的切屑锯齿化程度最高,约为0.36,易于自动断屑,更有利于切削的持续进行。

真空热处理强化AlCrSiN/Mo涂层研究

采用复合脉冲磁控溅射技术沉积AlCrSiN/Mo涂层,并利用真空热处理方式改善涂层微观结构和性能。利用SEM、XRD、EDS、纳米压痕仪、划痕仪、应力测试仪、摩擦磨损试验机分别对沉积态、600℃、700℃、800℃、900℃真空热处理后的AlCrSiN/Mo涂层元素成分、微观结构、力学性能及摩擦磨损性能进行测试。实验结果表明:经真空热处理后,AlCrSiN/Mo涂层仍保持nc-(Al,Cr,Mo)N/a-Si_(3)N_(4)的纳米复合结构,并沿(200)晶面择优生长,涂层中hcp-AlN相消失;涂层表面颗粒生长更加充分,组织结构更加致密,孔隙率减少;硬度、韧性及残余应力均有所增加,临界载荷下降,耐磨性能得到一定改善。当热处理温度达到900℃时,涂层表现出最好的综合性能,硬度H高达17.60 GPa,表面质量最佳,摩擦系数和磨损率最低,分别为0.61和1.69×10^(-3)μm^(3)/(N·μm),此时H/E和H^(3)/E^(*2)最高。

Mo含量对激光熔覆CoCrFeNiW_(0.6)Mo_(x)高熵合金涂层组织与性能的影响

目的研究Mo含量的变化对激光熔覆CoCrFeNiW_(0.6)高熵合金涂层的影响。方法使用RFL-C1000光纤激光器,在45钢基体表面制备CoCrFeNiW_(0.6)Mo_(x)(x=0,0.2,0.4,0.6,0.8)高熵合金涂层,并利用Leica DVM6光学显微镜、扫描电镜(SEM)、X射线衍射仪(XRD)、能谱仪、显微硬度仪、电化学工作站对熔覆层的宏观形貌与稀释率、相结构、微观组织结构、硬度、耐腐蚀性能进行测试与分析。结果加入Mo元素后,结合状态与表面形貌良好,当x=0~0.4时,涂层微观组织主要呈树枝晶形态,且晶粒逐渐变细。当x≥0.6时,涂层表面开始有裂纹产生。随着Mo元素的添加,涂层逐渐析出σ相,晶粒尺寸逐渐减小。当x=0.8时,有共晶组织形成。涂层显微硬度随Mo元素的增加而增加,但由于x=0.8时出现较多裂纹,裂纹的出现影响了涂层硬度,导致x=0.8时的硬度减小。当x=0.6时,涂层平均显微硬度最高,达到了959.69HV0.3,约为CoCrFeNiW_(0.6)涂层平均硬度的20.32%。当x=0~0.6时,涂层耐腐蚀性能随着Mo元素含量的增加逐渐提升。当x=0.8时,耐腐蚀性能变差,其原因是裂纹的出现以及σ相的形成使得涂层耐腐蚀性变差。在x=0.6时,涂层耐腐蚀性能最好。结论Mo元素的加入使得涂层微观组织出现σ相,同时有细化晶粒的作用,可以显著改善涂层的硬度以及耐腐蚀性。

Mo_(0.05)Ti_(1.95)Nb_(10)O_(29)/C复合负极材料的制备与性能研究

Ti_(2)Nb_(10)O_(29)具有理论容量高、结构稳定、安全性好等优势,是非常有应用前景的锂离子电池和锂离子电容器用新型负极材料,但其电子导电率极低,限制了应用。采用Mo掺杂和碳包覆双协同策略,经优化葡萄糖添加量所制Mo_(0.05)Ti_(1.95)Nb_(10)O_(29)/C复合负极材料显著提升了充放电性能,0.1C充放电的可逆容量达到了313.6mAh/g,10C倍率下的可逆容量比Ti_(2)Nb_(10)O_(29)的提升了72.3mAh/g,高达174.3mAh/g,且0.5C循环100圈后容量损失仅2.4%。第一性原理分析证明,该电性能的提升主要归因于Mo掺杂导致的Ti_(2)Nb_(10)O_(29)材料本征电子导电性提高及碳包覆导致的材料颗粒间电子传输行为改善。

Hot Corrosion Behavior of Sol-Gel Nano Structured Zirconia Coated 9Cr1Mo Ferritic Steel in Alkali Metal Chlorides and Sulphates Deposit Systems at High Temperatures

Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer. This results in an increase in oxidation rate of the metal. Since, zirconia coating is well recognized for corrosion protection under high temperature oxidative environment, we have developed zirconia coating on 9Cr1Mo ferritic steel and their oxidation performance was evaluated in LiCl-NaCl and Na2SO4-K2SO4 salts deposit system in air atmosphere at 650?C and 850?C, respectively. Before coating development, zirconium based sol was synthesized using zirconium (IV) propoxide as a precursor. Oxidation test results indicated that the zirconia coated specimens shows more than two times higher corrosion resistance in LiCl-NaCl and three time higher corrosion resistance in Na2SO4-K2SO4 salt deposit, respectively.