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。     

Y2O3改性石墨/CaF2/TiC/镍基合金复合涂层微观组织与摩擦学性能研究

为提高石墨/CaF₂/TiC/镍基合金（GCTN）复合涂层的力学性能和摩擦学性能,运用等离子喷涂技术在45钢表面制备了Y₂O₃改性GCTN复合涂层,研究了Y₂O₃对复合涂层的微观组织、显微硬度、断裂韧性和摩擦磨损性能的影响。结果表明：Y₂O₃改性GCTN复合涂层主要由γ-Ni、CrB、Cr7C₃、TiC、CaF₂和石墨等物相组成。Y₂O₃在等离子火焰加热作用下与C元素反应生成活性元素Y,Y净化了复合涂层的微观组织,并细化了CrB、Cr₃C7等硬质相晶粒,提高了其致密性。当Y₂O₃质量分数为0.5%时,复合涂层的显微硬度和断裂韧性分别为593.3MPa和6.82MPa·m^1/2,比不含Y₂O₃的复合涂层分别增大了8%和22%,其机理主要是Y₂O₃细化了CrB、Cr₃C₇等硬质相晶粒,起到了细化强化作用。由于GCTN-0.5Y₂O₃复合涂层的显微硬度和断裂韧性显著提高,减少了其黏着磨损和微观断裂磨损,因而GCTN-0.5Y₂O₃复合涂层的摩擦因数和磨损率最小,分别为0.085和0.39×10-3mm3/m。     

铝合金表面添加La_2O_3激光熔覆Ni基WC金属陶瓷涂层研究

添加适量La2O3,采用自配的熔覆材料在ZL108表面激光熔覆制备了Ni基WC金属陶瓷复合涂层,对熔覆层进行了显微组织和能谱分析、显微硬度测量以及室温下的干滑动摩擦磨损试验。结果表明,在铝合金表面激光熔覆处理时添加适量La2O3获得的Ni基WC金属陶瓷增强涂层无裂纹,组织细小,致密,WC颗粒增强相与基体之间结合良好。室温下熔覆层的磨损主要为显微切削和粘着磨损,干摩擦磨损性能优良。     

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,...     

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。     

高能离子源清洗对AlCrN刀具涂层结构及性能的影响

采用自主研发的离子源增强多弧离子镀设备,研究涂层沉积前不同清洗工艺对基材表面粗糙度以及所制备的AlCrN涂层的表面形貌、硬度、膜基结合力、摩擦磨损和切削性能的影响。研究结果表明,高能Ar⁺清洗可以更有效清洁基材表面。与传统弧源清洗技术相比,经高能离子源清洗后的基体表面粗糙度降低,沉积态涂层的表面粗糙度更低。相比于传统弧源清洗工艺,高能Ar⁺清洗可以显著提高膜基结合强度,达到48.7 N,摩擦因数和磨损率均降低,涂层刀具寿命提高了3倍。     

基于第一性原理的碳化铬陶瓷颗粒形貌预测及验证分析

采用激光熔覆技术制备碳化铬增强Ni60复合涂层,并对其生长形貌与生长机制进行研究和验证。基于第一性原理在Materials Studio(8.0)软件中对碳化铬晶体的生长形貌进行了预测,对Ni基相及Cr₃C₂陶瓷相的界面结合特性进行了仿真分析,对碳化铬陶瓷相的生长机制进行了研究,并通过熔覆实验对仿真结果进行了验证。实验验证时在Ni60粉末中添加一定含量的C粉及Cr粉,进行球磨作为涂层粉末,采用激光熔覆技术在H13钢表面原位生成碳化铬镍基复合涂层,通过X射线衍射仪(XRD)和扫描电镜(SEM)对涂层的物相和显微组织进行分析,采用维氏硬度计对涂层的显微硬度进行测试。研究结果表明,碳化铬生成相形貌主要为四边形、六边形以及其他不规则形貌,与仿真结果中形貌预测的结果一致。涂层平均显微硬度达到700 HV,是基体硬度的3倍。四边形碳化铬主要为Cr₃C₂,六边形碳化铬以Cr₇C₃为主,不规则形碳化铬为Cr₇C₃和Cr_...     

Al2O3-13%TiO2/铁基非晶合金复合涂层的室温摩擦磨损行为

利用等离子喷涂技术制备含质量分数15%Al₂O₃-13%TiO₂陶瓷相的Fe₄₅Cr₁₆Mo₁₆C₁₈B₅铁基非晶合金复合涂层并进行销盘式摩擦磨损试验，通过与铁基非晶合金涂层进行对比，研究了复合涂层在不同载荷(20,30,50 N)和销轴转速(300,500,800 r·min^-1)下的摩擦磨损行为，分析了其磨损机制。结果表明：当销轴转速为300 r·min^-1时，不同载荷下复合涂层的磨损率较铁基非晶合金涂层降低近50%,复合涂层的磨损机制随着载荷的增大由磨粒磨损转变为疲劳磨损；当载荷为30 N时，复合涂层的磨痕深度与磨损率随销轴转速的增加先增大后减小，均在转速为500 r·min^-1达到最大，在销轴转速为500 r·min^-1和800 r·min^-1时复合涂层均表现为黏着磨损。     

喷砂嘴内表面真空高频感应熔覆制备耐磨涂层及其性能

采用真空高频感应熔覆技术在45钢喷砂嘴内表面熔覆制备添加20%(质量分数)WC的Ni60A合金涂层,并分别采用车床和电火花成型机床进行扩孔,分析了涂层和基体的显微组织和硬度分布,并研究了该涂层的摩擦磨损性能。结果表明:涂层具有良好的熔覆质量,平整无裂纹,存在少量孔洞,涂层与基体间为冶金结合;与车床扩孔后的相比,经过电火花成型机床扩孔后涂层外层组织的孔隙率下降,组织更加细化;涂层的硬度远高于基体的,电火花成型机床扩孔涂层外层的硬度高于车床扩孔的;经过150min冲蚀磨损试验后,涂层喷砂嘴的磨损量是未涂层喷砂嘴的11%,涂层喷砂嘴和未涂层喷砂嘴的摩擦因数分别为0.16和0.22,涂层喷砂嘴的耐磨性能显著提高。     

WC颗粒增强镍基涂层改善制动盘组织与磨损性能

为提高汽车制动盘耐磨和高温氧化性能,延长其使用寿命,采用激光熔覆技术在中碳钢表面制备了以WC颗粒为增强相的Ni基复合涂层.借助SEM和XRD等表征手段对制动盘表面涂层进行了组织和物相分析,利用维氏硬度计测试了制动盘表面涂层截面显微硬度分布,通过摩擦磨损实验研究了制动盘表面涂层的磨损性能.研究表明,制动盘表面涂层主要由γ-（Ni,Fe）固溶体、均匀分布WC颗粒和碳化物抗磨损相组成.涂层平均显微硬度HV0.2670,显微硬度值波动较小较为平稳,证明涂层组织比较均匀.在多种强化效果共同作用下,制动盘表面涂层的磨损量与基材相比明显减小,仅为基材的20％,抗磨损性能显著提高.     

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.     

On the wear characteristics of cobalt-based hardfacing layer after thermal fatigue and oxidation

High temperature wear characteristics of Stellite 6 alloy containing Cr₃C₂ after thermal fatigue and oxidation treatment at 700°C were investigated. The hardfacing layer was deposited by plasma transferred arc (PTA) process. After thermal fatigue treatment, cracks propagated along boundaries of incoherent chromium carbide particles. Significant oxidation occurred mainly on the clad layer containing Cr₃C₂. The wear test results revealed a slightly higher wear volume on Stellite 6 with Cr₃C₂ due to the existence of cracks. The formation of oxide on the surface could effectively reduce the wear volume by reducing the real contact area between mating surfaces. Lower sliding speed resulted in higher wear volume. The mechanism was interpreted by the friction coefficient change during sliding wear. Wear test results were further interpreted by investigating the wear trace via SEM. Possible wear mechanisms were postulated. Analysis of wear debris showed severe oxidation on the Stellite 6 with Cr₃C₂. It could be concluded that oxidation on the clad layer was beneficial to the wear resistance at elevated temperature. Thermal fatigue cracking on the surface might be detrimental to the wear resistance, however, this could be partly compensated by the existence of oxide.     

等离子喷涂WC/Co Fe基涂层摩擦与磨损性能

以普通铸铁为基体,碳化钨陶瓷粉末WC 12Co为热喷涂材料,采用大气等离子法制备WC/Co Fe复合涂层.通过SEM、EDS、XRD等手段对WC/Co Fe涂层微观组织与结构进行表征,并对WC/Co Fe复合涂层耐磨损性能进行测试.结果表明,等离子喷涂制备的WC/Co Fe涂层物相以WC相为主;WC涂层摩擦因数波动小于铸铁材料摩擦因数,表明WC复合涂层具有良好的抗摩擦性能.WC涂层耐磨损性能高于铸铁,主要归因于WC颗粒韧性好、硬度高、抗冲击及抗磨损性能强,与基体金属的结合性好.     

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.     

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。     

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.     

Analysis of the friction and wear mechanisms of multilayered plasma-sprayed ceramic coatings

Wear tests were conducted on a rotor-vane-disk adaptor where three rotating vanes were pressed against a disk. Vanes were coated by WC and used as the upper specimen while the disk was coated by Cr₂O₃ and used as the lower specimen. A buffer layer of various thicknesses and contents was placed between the top coating and the bulk steel of the disk to alleviate the effects of the large difference in thermal properties of the two materials. The experimental results reveal that correct placement of a buffer layer can indeed improve the wear resistance. Factors such as the temperature to which the specimen was heated before testing, the proportion by weight of each individual constituent in the buffer layer, and the thickness of each coating layer, were also important for the volume of wear of the lower specimen. As the specimens were heated to higher temperatures, the wear volume decreased with increasing proportions of Cr₂O₃ in the buffer layer. Elevating the preheating temperature of the specimens can diminish the wear volume but increases the friction coefficient. The steady-state wear rate is not much influenced by the constituents of the buffer layer and the coating thickness. Brittle fracture, abrasion, adhesion and oxidation were found to be the primary wear mechanisms in the tests.