基于响应曲面法优化大气等离子喷涂Y2O3涂层工艺

以自制的高纯Y₂O₃粉为原料，借助大气等离子喷涂工艺在A6061铝合金表面制备Y₂O₃涂层，基于响应曲面法构筑了相应的响应曲面图，分析了喷涂电压(60～80 V)、喷涂电流(500～600 A)和喷涂距离(100～120 mm)的交互作用对涂层硬度和孔隙率的影响，优化了等离子喷涂工艺。结果表明：基于响应曲面法建立了涂层显微硬度和孔隙率的二次数学模型；模型预测Y₂O₃涂层的优化工艺参数为喷涂电压78 V、喷涂电流500 A、喷涂距离120 mm,涂层的显微硬度和孔隙率分别为633.28 HV和3.22%,与试验值的相对误差分别为1.92%和1.26%,验证了模型的准确性。优化工艺下制备的涂层表面粗糙度为5.733μm,结合强度为25.6 MPa。     

CeO2添加量对激光熔覆TiB2-TiC/Ni复合涂层组织和性能的影响

利用激光熔覆技术在TC4钛合金表面制备了添加质量分数1.0%,1.5%,2.0%CeO₂的TiB₂-TiC/Ni复合涂层,研究了复合涂层的物相组成、显微组织和硬度,讨论了搭接率(30%,40%,50%)对最佳CeO₂含量条件下复合涂层试样摩擦磨损性能的影响。结果表明：复合涂层均由TiB₂、TiB、α-Ti、TiC、Ni₃Ti、Cr₂₃C₆、Ti₂Ni、Cr₃C₂、γ-Ni等相组成;添加质量分数1.5%CeO₂复合涂层的组织最为均匀致密,细化效果明显;随着CeO₂添加量的增加,复合涂层的硬度先增后降,添加质量分数1.5%CeO₂复合涂层的硬度最高,约为1 015 HV。CeO₂的最佳添加质量分数为1.5%,在此条件下随着搭接率的增加,试样的磨损质量损失先减小后增大,当搭接率为40%时,...     

Cr2O3掺杂量对SnO2压敏电阻微观结构和电气性能的影响

以SnO₂粉、CuO粉、Nb₂O₅粉、Cr₂O₃粉为原料,采用粉末冶金技术烧结制备(98.95-x)SnO₂-1CuO-0.05Nb₂O₅-xCr₂O₃(x=0,0.01,0.02,0.03,0.05,物质的量分数/%)压敏电阻,研究了Cr₂O₃掺杂量对该压敏电阻微观结构和电气性能的影响。结果表明：随着Cr₂O₃掺杂量的增加,烧结试样的相对密度、收缩率、平均晶粒尺寸均先增大后减小,当Cr₂O₃物质的量分数为0.02%时相对密度和收缩率最高,Cr₂O₃物质的量分数为0.01%时晶粒尺寸最大,粒径分布最均匀;随着Cr₂O₃掺杂量增加,SnO₂     

Sb-SnO2掺杂量对Al2O3-13%TiO2复合陶瓷涂层抗结垢性能的影响

以Al₂O₃-13%TiO₂(AT13)和纳米掺锑SnO₂(Sb-SnO₂)粉体为原料,采用等离子喷涂工艺在4145H合金钢基体表面制备了掺杂不同质量分数(0～16%)Sb-SnO₂的AT13复合陶瓷涂层,研究了复合陶瓷涂层的表面性能、微观形貌、显微硬度、结合强度以及在地层采出水中的抗结垢性能,并与电镀铬层和未处理4145H合金钢进行对比。结果表明：与电镀铬层和未处理4145H合金钢相比,复合陶瓷涂层的水接触角较大,表面能较低,随着Sb-SnO₂掺杂量的增加,水接触角基本呈先增大后减小的趋势,表面能先减小后增大;复合陶瓷涂层具有大量的孔隙;随着Sb-SnO₂掺杂量的增加,硬度整体呈降低趋势,但均高于4145H合金钢和电镀铬层,单位面积结垢质量先减小后增大;掺杂质量分数10%Sb-SnO₂的复合陶瓷涂层具有最大的水接触角、最小的表面能、最小的单位面积结垢质量,平均结合强度为25.7 MPa。     

La2O3添加量对激光熔覆铁基合金涂层显微组织和耐磨性能的影响

采用激光熔覆技术在35CrMoV钢表面制备添加La₂O₃质量分数分别为0,0.7%,1.4%,2.0%的铁基合金熔覆层,研究了La₂O₃含量对其显微组织、物相组成、显微硬度、耐摩擦磨损性能和抗冲击磨料磨损性能的影响。结果表明：未添加La₂O₃的熔覆层主要物相为FeCr固溶体和少量Cr₂₃C₆,添加La₂O₃后熔覆层中还出现了LaNi₃,当La₂O₃质量分数为1.4%时熔覆层与基体界面平整,冶金结合良好,组织细小且均匀;随着La₂O₃质量分数增加,熔覆层显微硬度先增大后减小,耐摩擦磨损性能和抗冲击磨料磨损性能先提高后降低,当La₂O₃质量分数为1.4%,耐磨性能最好,此时熔覆层的摩擦磨损机制由未添加La₂     

TiC含量对无压烧结TiC-Al2O3导电陶瓷复合材料微观结构与性能的影响

以Al₂O₃、TiC粉体为原料,采用无压烧结技术制备了TiC-Al₂O₃导电陶瓷复合材料,研究了TiC体积分数(30%～45%)对陶瓷复合材料微观结构和性能的影响。结果表明：TiC-Al₂O₃导电陶瓷复合材料主要由Al₂O₃和TiC两相组成;随着TiC含量的增加,陶瓷复合材料的相对密度降低,开口气孔率增大,当TiC体积分数为30%时,相对密度最大,开口气孔率最低,分别为95.5%和3.0%;陶瓷复合材料中导电相TiC均连接为网状结构,随着TiC含量的增加,TiC所形成的网状结构越发完整,陶瓷复合材料的硬度先升高后降低,电阻率和断裂韧度均呈降低趋势,抗弯强度增大;当TiC体积分数为45%时,陶瓷复合材料的抗弯强度最高,电阻率最低,分别为361 MPa和6.95×10^-6Ω·m。     

激光功率对选区激光熔化Al2O3/ZrO2(Y2O3)缺陷与力学性能分析

利用选区激光熔化技术对Al₂O₃/ZrO₂(Y₂O₃)陶瓷粉末进行3D打印试验研究,分析在不同激光功率条件下的缺陷与力学性能。试验结果表明：激光功率对打印过后陶瓷样品缺陷的生成有重要影响。在一定条件下随着激光功率的增加,气孔、裂纹等缺陷减少,并在激光功率为300 W时表现最好,且此时显微维氏硬度最大值约为17.5 GPa。     

WC添加量对等离子喷涂Mo2FeB2金属陶瓷涂层组织和耐腐蚀性能的影响

采用等离子喷涂法在Q235钢表面制备不同质量分数(0,10%,15%,20%,25%)WC改性Mo₂FeB₂金属陶瓷涂层,研究了WC添加量对涂层物相组成、显微组织和耐腐蚀性能的影响。结果表明：WC改性Mo₂FeB₂金属陶瓷涂层均主要由Mo₂FeB₂、WC、W₂C、铁和铁的氧化物相组成;当WC质量分数由0增加至15%时,金属陶瓷涂层的Mo₂FeB₂和WC双硬质相数量增多,尺寸减小,分布趋于均匀,当WC质量分数超过15%时,双硬质相发生聚集,孔隙率增大,涂层致密性下降;当WC质量分数为15%时,涂层组织最均匀致密,耐腐蚀性能最好。     

掺杂Y2O3钨基复合材料在近韧脆转变温区的静载拉伸特性

制备了掺杂质量分数分别为0.5%,2.0%Y₂O₃的钨基复合材料,研究了其显微组织,通过不同温度(25～800℃)下的拉伸试验分析了其近韧脆转变温区的变形特性。结果表明：2种复合材料均存在由轧制变形导致的大量位错,Y₂O₃颗粒对位错运动起到钉扎作用;Y₂O₃掺杂质量分数为2.0%的复合材料的晶粒更细小,发生韧脆转变的温度更低,在300～400℃拉伸时发生半脆性行为,断口区域位错密度在3.8×10¹⁵～3.9×10¹⁵ m^-2,在600～800℃下发生明显塑性变形,位错密度增加至6.2×10¹⁵～6.8×10¹⁵ m^-2。     

送粉速率对等离子喷涂Mo2NiB2基金属陶瓷涂层性能的影响

采用大气等离子喷涂法在Q235钢基体表面制备Mo₂NiB₂基金属陶瓷涂层,研究了送粉速率(40～80 g·min^-1)对Mo₂NiB₂涂层硬度、结合强度、耐腐蚀性能的影响。结果表明：不同送粉速率下Mo₂NiB₂涂层主要由Mo₂NiB₂陶瓷相、MoNi₄合金相和MoB₂硬质相组成,在送粉速率为60 g·min^-1时涂层质量最佳;随着送粉速率的增大,Mo₂NiB₂涂层的硬度和结合强度先提高后下降,且均在送粉速率为60 g·min^-1时达到最大,分别为2 107 HV,29.23 MPa; Mo₂NiB₂涂层的耐腐蚀性能随送粉速率的增大而增强,在送粉速率为80 g·min^-1时达到最佳。     

纳米Fe-Al/Cr_3C_2复合涂层及其抗高温腐蚀性能

制备纳米金属间化合物Fe-Al/Cr_3C_2复合涂层并测试其抗腐蚀性能,为利用热喷涂技术治理火电站易损部件腐蚀问题提供有效手段。运用自主研发的造粒系统,成功对高活性的纳米Fe-Al/Cr_3C_2复合喷涂粉体实施团聚造粒;运用高速火焰喷涂方法,在结构材料表面制备出了纳米Fe-Al/Cr_3C_2复合涂层,对比测试了微米、纳米Fe-Al/Cr_3C_2复合涂层的抗高温腐蚀性能,分别采用抛物线型和幂函数型对腐蚀动力学曲线进行拟合。纳米Fe-Al/Cr_3C_2复合喷涂材料的粒径由原始的50nm团聚到最终的114~178μm,团聚后的纳米颗粒呈圆形或椭圆形,各成分比例保持原始比例,团聚颗粒内部仍然保持纳米粉体状态;纳米Fe-Al/Cr_3C_2复合涂层表面致密、铺展均匀,截面元素过渡平缓、层片细小;运用幂函数方程对腐蚀动力学曲线的拟合效果更好。通过对腐蚀动力学拟合方程进行求导运算可推算出各复合涂层的腐蚀速率。团聚后的纳米颗粒满足热喷涂材料的相关要求,纳米Fe-Al/Cr_3C_2复合涂层的抗高温腐蚀性能显著高于微米Fe-Al/Cr_3C_2复合涂层。纳米Al、Cr优先氧化生成具有保护作用的氧化膜机理解释了纳米涂层抗高温腐蚀性能优异的原因。     

Improvement in tribological properties of plasma-sprayed Cr3C2–NiCr coating followed by electroless Ni-based alloy plating

Electroless-plated Ni-based alloy coatings, Ni, Ni–Co and Ni–Mo coatings with thickness less than 5 μm were deposited on surfaces of plasma-sprayed Cr₃C₂–NiCr coating. The tribological properties of these electroless-plated coatings against the as-sprayed Cr₃C₂–NiCr coating as sliding pairs were investigated with a block-on-ring arrangement in air at room temperature. It was found that all the Ni-based alloy coatings effectively improved the tribological properties of the Cr₃C₂–NiCr coating. Especially when the Cr₃C₂–NiCr coatings plated with Ni–Co and Ni–Mo coatings were against the as-sprayed Cr₃C₂–NiCr coating as sliding pairs, friction coefficients of 0.10 to 0.13 and coefficients wear coefficients less than 10⁻⁶ mm³·N⁻¹·m⁻¹ were achieved. Through examination and analysis of the worn surfaces employing scanning electron microscopy and X-ray photoelectron spectrometer, the improvement in tribological properties of the Cr₃C₂–NiCr coating may be attributed to the transformation of wear mechanism and the formation of CrO₃ on the worn surfaces.     

Counterface effects on the wear of a composite dry-bearing liner

Plastics-based dry-bearing liners used for flight control bearings in aircraft are usually mated against counterfaces of 440C stainless steel hardened to about 700 HV and finished to R_a ≈ 0.05 μm. In this paper experiments to examine the possibility of reducing liner wear by modifications to the counterface are described. Accelerated (pin-on-disc) tests were made against 440C stainless steel of varying hardness and roughness, electroplated with copper and cadmium, ion implanted with nitrogen, copper and cadmium, vacuum deposited with TiN and TiC, diffusion treated with nitrogen, boron, sulphur, Sn-Cu and Sn-Sb and coated with ceramics-cermets (Al₂O₃, Cr₂O₃, (Cr₂C₃)-Ni-Cr and WC-Co). The most important counterface properties influencing liner wear are the hardness and surface roughness, and for ceramic and cermet coatings, the harder and smoother the surface, the lower is the liner wear. No evidence was found to indicate that the chemical nature of the counterface has a major affect on the liner wear.     

Evaluation of wear and tribological properties of coatings rubbing against copper

A new crossed-cylinders tribo-tester is proposed. This tribo-tester can decrease the tendency of the chatter vibration. The tribological properties of coatings against copper is evaluated with this tribo-tester. The wear rate of TiN, TiC and TiCN rubbing against copper is higher than the substrate high speed tool steel: SKH51 (JIS). The catalytic action of copper for oxidation of Ti-based coatings is a main reason of this high wear rate of TiN, TiC and TiCN rubbing against copper. The wear rate of CrN rubbing against copper is in a very low level because CrN shows the excellent oxidation resistance and Cr₂O₃ film formation decreases the wear loss of CrN coating.     

Adhesion, friction and wear of thin hard coatings

Chemically vapour-deposited and physically vapour-deposited coatings of hard and wear-resistant materials such as TiC, TiN, Ti(C, N), Cr₇C₃, Al₂O₃, SiO₂ and TiO₂ as well as other carbides, nitrides, borides, oxides and combinations thereof are increasingly used in industrial applications to protect metal, ceramic and in certain cases polymer parts against mechanical and chemical attack, sometimes with a decorative purpose also. Some relevant examples of coated products are cemented carbide throwaway cutting tips (TiC, TiN, Ti(C, N), Al₂O₃ etc.), high speed steel drills and milling cutters (TiN), hobs, deep drawing tools, ball-bearing elements, gears, machine elements, electrical contacts, body implants, surgical instruments and tools, cutlery, fuel pins and armatures especially for helium- and sodium-cooled nuclear reactors, low Z sputter-resistant protective coatings on parts (limiters, antennae etc.) and walls of the torus in fusion reactors (tokamak) and gold- or silver- or black-coloured watch cases and jewelry pieces. The life of such coated tools or machine elements as well as their performance are considerably increased, provided that the adhesive strength of the coating to the base material and the intrinsic cohesion of the coating are sufficient. Bad adhesion leads to flaking (adhesive failure) while poor cohesion causes chipping (cohesive failure).     

General aspects for tribological applications of hard particle coatings

Hard coatings, consisting of WC, TiC or Cr₃C₂ particles with a nickel or cobalt matrix were compared with conventional wear-resistant materials like hardened steel 100 Cr6, Ferro TiC P143, WC-Co hard metal and a widely used thermal spray layer NiCrBSi. The coating procedure was flame spraying and diffusion welding. Some layers were remelted using an electron beam to improve their microstructural properties, porosity and binding to the bulk material.

Wear tests were performed under different degrees of severity to qualify the resistance of the coating, using abrasive, sliding and impact test methods representing different wear mechanisms. It is shown that the benefit of the hard particle content depends on the acting loading situation. Under abrasive and sliding conditions the advantage of a high hardness level, i.e. a high concentration of hard phases, could be demonstrated. For impact loading, causing severe surface fatigue, homogeneous materials with high toughness, such as martensitic steels, are beneficial; followed by coatings with a high concentration of ductile matrix. In some cases, the weaknesses, such as brittleness and limited strength of binding to the bulk, could be improved by electron beam remelting.     

Friction coefficient and wear rate of sputter-deposited thin films and plasma-sprayed thick coatings at high temperatures in room air

Silver, calcium fluoride (CaF_x with x = 1.85) and chromium-carbon (Cr₃C₂) thin films were deposited onto various tribological test specimens by sputtering. The friction properties of sputter-deposited Ag and CaF_x single layers as well as Ag/CaF_x multilayer films were determined by ball-on-disk tribological tests conducted in room air under various experimental conditions. The tribological properties (friction coefficient and wear rate) of sputter-deposited CaF_x films were also determined at 500°C by pin-on-disk tribological tests performed with pin specimens made of cobalt-based alloy (alacrite). Chromium-carbon films sputter-deposited onto alacrite disk and counterfaces were found to be of interest for reducing the formation of alacrite wear debris in the wear tracks; thus reduced friction coefficient and wear rate values were obtained. The friction behavior of sputter-deposited CaF_x/Cr₃C₂ thin bilayer structures and plasma-sprayed (PS) chromium carbide/Ag/BaF₂-CaF₂ eutectic composite coatings (PS-212 type coatings) was investigated by plane-on-plane tribological tests conducted in room air at 500°C and 700°C. The friction performance of solid lubricant thin bilayer films was compared with that of thick PS-212 type coatings similar to coatings developed by NASA.     

Microstructure and wear properties of in situ TiC/FeCrBSi composite coating prepared by gas tungsten arc welding

Using a gas tungsten arc welding (GTAW) process, in situ synthesis TiC particles reinforced Fe-based alloy composite coating has been produced by preplaced FeCrBSi alloy, graphite and ferrotitanium powders. The microstructure and wear properties of the composite coatings were studied by means of scanning electron microscopy (SEM), X-ray diffractometer (XRD) and wear test. The effects of thickness of the pre-placed powder layer on the microstructure, hardness and wear resistance of the composite coatings were also investigated. The results indicated that TiC particles were produced by direct metallurgical reaction between ferrotitanium and graphite during the GTAW process. TiC particles with sizes in the range of 3–5 μm were dispersed in the matrix. The volume fraction of TiC particles and microhardness gradually increased from the bottom to the top of the composite coatings. The TiC-reinforced composite coatings enhance the hardness and wear resistance. The highest wear resistance of the composite coating with a 1.2 mm layer was obtained.     

Microstructure and wear properties of in situ TiC/FeCrBSi composite coating prepared by gas tungsten arc welding

Using a gas tungsten arc welding (GTAW) process, in situ synthesis TiC particles reinforced Fe-based alloy composite coating has been produced by pre-coated FeCrBSi alloy, graphite and ferrotitanium powders on the substrate. The microstructure and wear properties of the composite coatings were studied by means of scanning electron microscopy (SEM), X-ray diffractometer (XRD) and wear test. The effects of thickness of the pre-coated powder layer on the microstructure, hardness and wear resistance of the composite coatings were also investigated. The results indicated that TiC particles were produced by direct metallurgical reaction between ferrotitanium and graphite during the GTAW process. TiC particles with sizes in the range of 3–5 μm were dispersed in the matrix. The volume fraction of TiC particles and microhardness gradually increased from the bottom to the top of the composite coatings. The TiC-reinforced composite coatings enhance the hardness and wear resistance. The highest wear resistance of the composite coating with a 1.2 mm layer was obtained.     

高温耐磨球阀密封面涂层强化工艺的研究

介绍了采用超音速火焰喷涂(HVOF)工艺结合物理气相沉积(PVD)技术在Cr₃C₂-NiCr涂层上沉积CrN涂层形成CrN/Cr₃C₂-NiCr复合涂层的强化工艺,并对复合涂层从薄膜微观结构设计、摩擦、腐蚀及减磨防腐机理方面进行了研究。