Silver diffusion and high-temperature lubrication mechanisms of YSZ–Ag–Mo based nanocomposite coatings

Yttria-stabilized zirconia (YSZ) nanocomposite coatings consisting of silver and molybdenum were produced by a hybrid process of filtered vacuum arc, magnetron sputtering and pulsed laser depositions for tribological investigations at different temperatures. The coatings with 24 at.% Ag and 10 at.% Mo contents showed a friction coefficient of 0.4 or less for all temperatures from 25 to 700 °C. The wear scar surfaces and coating cross-sections were studied using scanning electron, transmission electron, scanning transmission electron and focused ion beam microscopes, which also provided the information on chemical composition distributions of silver and molybdenum along with microstructure features. It was demonstrated that silver diffusion and coalescence on surfaces played an important part in the high-temperature lubrication mechanism of the YSZ–Ag–Mo coatings. Silver was found to be an effective lubricant at temperatures below 500 °C and its coalescence on the surface isolated molybdenum inside coatings from ambient oxygen. Lubricious oxides of molybdenum were formed and lubricated at temperatures above 500 °C when the silver was worn off the contact surface. For silver containment inside the coating at high temperatures, a multilayer architecture was built by inserting a TiN diffusion barrier layer in the composite coatings. Microscopic observations showed that this barrier layer prevented silver exit to the coating surface. At the same time, this enabled a subsequent lateral lubricant supply toward a wear scar location where the diffusion barrier layer was worn through and/or for a next thermal cycle. The multilayer coating maintained a friction coefficient of 0.4 or less for more than 25,000 cycles, while the monolithic coating lasted less than 5000 cycles. In addition, a TiN surface barrier layer with pinholes was deposited on the YSZ–Ag–Mo composite surface to control vertical silver diffusion. With this coating design, the coating wear lifetime was significantly increased beyond 50,000 cycles.     

Ag/Bi2Sr2CaCu2Ox复合材料摩擦学特性

釆用固态反应法合成超导体Bi₂Sr₂CaCu₂O_x(Bi2212),使用摩擦实验机从液氮温度至室温对其摩擦学特性进行研究。研究表明：室温Bi2212与不锈钢盘对摩时摩擦系数约为0.35,当温度降至超导转变温度以下(液氮温度),摩擦系数大幅度降低至0.11,非常稳定。为改善Bi2212常温摩擦性能,添加Ag制备出Ag/Bi2212超导复合材料,XRD、SEM和EDS分析表明,Ag未进入Bi2212晶格,保证了Bi2212的超导电性,Ag的添加提高了复合材料密度和韧性,在正常载荷和滑行速度下Ag质量分数为10 %时摩擦系数为0.2,15%Ag/Bi2212磨损率最低,为9. 5×10-5 mm3 (N·m)-1。分布基体中的Ag能有效抑制裂纹萌生和扩展并在摩擦作用下向表面转移,在摩擦表面形成一层Ag转移膜,其低剪切强度起到很好的润滑作用,同时将摩擦产生的热量及时传导出去,使复合材料表现出良好的减摩耐磨性能。     

TiAlSiN-Ti(Mo)N/MoS2复合涂层微观结构及摩擦学性能的研究

采用磁控溅射技术在AISI-304不锈钢上制备了TiAlSiN-Ti(Mo)N/MoS2复合涂层。采用电子显微镜(SEM)、X射线衍射仪(XRD)、显微硬度计、球盘摩擦磨损试验机、表面形貌仪等对涂层的表面形貌、显微组织、硬度和摩擦学性能进行了系统的研究。结果表明TiAlSiN-Ti(Mo)N/MoS2复合涂层的硬度为27.56 GPa,相比于TiAlSiN涂层的硬度(29.1 GPa)有所下降,但是涂层的耐磨性能得到明显提高。在室温至600℃条件下TiAlSiN-Ti(Mo)N/MoS2复合涂层的主要磨损机理为黏着磨损,200和400℃时的磨损率分别为0.0339×10^-3和0.1122×10^-3mm^3/(Nm),相较于TiAlSiN涂层分别降低了38%和57%,600℃时的磨损率接近TiAlSiN涂层。总体来说TiAlSiN-Ti(Mo)N/MoS2复合涂层的性能高于单一的TiAlSiN涂层。     

Tribological properties of transition metal di-chalcogenide based lubricant coatings

Transition metal di-chalcogenides MX₂ (X= S, Se, Te; and M= W, Mo, Nb, Ta) are one kind of solid lubricant materials that have been widely used in industry. The lubricant properties of such lubricant coatings are dependent not only on microstructure, orientation, morphology, and composition of the coatings, but also on the substrate, the interface between substrate and lubricant coatings, and the specific application environment. In this review, the effects of parameters on tribological properties of such kind of lubricant coatings were summarized. By comparing advantages and disadvantages of those coatings, the special treatments such as doping, structural modulation and post-treatment were suggested, aiming to improve the tribological performance under severe test conditions (e.g. high temperature, oxidizing atmosphere or humid condition).     

真空等离子体喷涂B4C-Mo复合涂层耐磨性能研究

采用真空等离子体喷涂技术制备了B₄C-Mo复合涂层, 并对其耐磨性能进行了研究。与B₄C纯涂层相比, 复合涂层结构更为致密, (B, Mo)C过渡相的存在改善了B₄C相与Mo相之间的润湿性, 进而有效提高了涂层的抗摩擦磨损性能。此外, Mo在喷涂过程中形成了大量的纳米晶, 这也在一定程度上促进了复合涂层耐磨性能的提高。     

Cu／C复合润滑剂的摩擦学性能

将纳米Cu和纳米金刚石复配成Cu／C复合添加剂,对Cu／C复合添加剂在500SN基础油中的减摩抗磨性能进行了研究。结果表明：Cu／C复合试油能明显改善500SN基础油的摩擦学性能,当纳米Cu的添加量为4％,纳米C的添加量为2％时,Cu／C复合试油的减摩效果最好,同500SN空白试油相比,摩擦系数可降低94．8％;当纳米Cu的添加量为3％,纳米C的添加量为4％时,Cu／C复合试油的抗磨效果最好,同500SN空白试油相比,磨损量减少108．6％。     

界面改性对SiC_p/Cu复合材料热物理性能的影响

采用热压烧结法成功制备SiC_p/Cu复合材料。采用溶胶-凝胶工艺在SiC颗粒表面制备Mo涂层,研究Mo界面阻挡层对复合材料热物理性能的影响。结果表明:过氧钼酸溶胶-凝胶体系能够在SiC颗粒表面包覆连续性、均匀性较好的MoO_3涂层,最佳工艺配比为SiC∶MoO_3=5∶1(质量比)、过氧化氢∶乙醇=1∶1(体积比),SiC表面丙酮和氢氟酸预清洗处理有利于MoO_3涂层的沉积生长。MoO_3在540℃第一步氢气还原后转变为MoO_2,MoO_2在940℃第二步氢气还原后完全转变为Mo,Mo涂层包覆致密完整。热压烧结SiC_p/Cu复合材料微观组织致密均匀,且相比原始SiC颗粒增强的SiC_p/Cu,经溶胶-凝胶法界面改性处理的SiC_p/Cu复合材料热导率明显提高,SiC体积分数约为50%时,SiC_p/Cu复合材料热导率达到214.16W·m~(-1)·K~(-1)。     

Mo2Ni3Si/NiSi复合材料涂层的滑动磨损行为

以Mo-Ni-Si合金粉末为原料，使用激光熔敷技术在1Crl8Ni9Ti不锈钢基材表面制备出Mo2Ni3Si／NiSi金属硅化物复合材料涂层．应用OM，SEM，EDS和XRD方法分析了涂层的显微组织．Mo2Ni3Si／NiSi复合材料涂层由初生的Mo2Ni3Si三元金属硅化物树枝晶和枝晶间的Mo2Ni3Si／NiSi共晶组织组成．在常温和高温滑动磨损条件下测试了涂层的耐磨性能．在常温滑动磨损条件下，Mo2Ni3Si／NiSi金属硅化物复合材料涂层的质量损失随着载荷的增加缓慢增加；在高温滑动磨损条件下，Mo2Ni3Si／NiSi金属硅化物复合材料涂层的质量损失随着温度的升高缓慢下降．     

真空退火温度对AlCrSiN/Mo自润滑涂层结构与性能的影响

采用高功率脉冲磁控溅射与脉冲直流磁控溅射复合镀膜技术制备AlCrSiN/Mo自润滑涂层,通过真空退火处理改善其结构和性能。利用扫描电镜、X射线衍射仪、电子探针分析仪、纳米压痕仪、划痕测试仪及摩擦磨损试验机,系统研究真空退火温度对涂层组织结构、力学性能及耐磨性能的影响。结果表明:所有AlCrSiN/Mo涂层均是a-Si3N4非晶相包裹nc-(Al,Cr,Mo)N的纳米复合结构。经真空退火后,涂层表面颗粒尺寸明显增大,对应纳米硬度与临界载荷均出现下降,而耐磨和减摩性能得到显著改善。当退火温度为700℃时,涂层的综合性能最佳,纳米硬度为18.3GPa、摩擦因数为0.51、磨损率为3.4×10^-4μm^3·(N·μm)^-1,此时特征值H/E和H3/E*2亦最高。     

脉冲激光沉积VN/Ag复合薄膜的组织及摩擦学性能研究

利用脉冲激光沉积技术制备了不同Ag含量的VN/Ag复合薄膜,利用扫描电子显微镜、X射线衍射仪、纳米力学测试系统等设备袁征薄膜的组织结构、成分、表面形貌及力学性能,利用UMT-3摩擦试验机考察薄膜在室温至900℃下的摩擦学性能.结果表明,随着Ag含量的增多,薄膜的组织形貌变差,硬度及弹性模量降低.当Ag含量为16％(原子分数)时薄膜在试验温度范围内的摩擦学性能最佳.由于Ag在低温的润滑特性及高温摩擦化学反应生成了新的润滑相,如V2O5、V6O11、V6O13、Ag3VO4、AgVO3等,使得摩擦系数随温度的升高而逐渐降低,在900℃下取得最低值0.08,实现了宽温域内的连续润滑.     

热处理对冷喷涂Cu-20%Al_2O_3复合涂层耐磨损性能的影响研究

利用冷喷涂技术制备Cu-20%(质量分数)Al2O3复合涂层,并在氩气保护气氛下对该复合涂层进行300℃、500℃和700℃退火热处理。采用常温干摩擦试验评价热处理对冷喷涂Cu-20%(质量分数)Al2O3复合涂层耐磨损性能的影响,并利用扫描电镜(SEM)观察涂层表面磨痕形貌。结果表明,复合涂层经退火热处理后发生了再结晶现象,涂层显微硬度降低。冷喷涂态和退火态复合涂层磨损机制不同:冷喷涂态复合涂层和低温退火热处理(300℃和500℃)下复合涂层磨损主要为磨粒磨损,700℃退火态复合涂层主要表现为疲劳磨损。     

Tribological properties of self-lubricating NiAl/Mo-based composites containing AgVO3 nanowires

Silver vanadate (AgVO₃) nanowires were synthesized by hydrothermal method and self-lubricating NiAl/Mo-AgVO₃ composites were fabricated by powder metallurgy technique. The composition and microstructure of NiAl/Mo-based composites were characterized and the tribological properties were investigated from room temperature to 900 °C. The results showed that NiAl/Mo-based composites were consisted of nanocrystalline B2 ordered NiAl matrix, Al₂O₃, Mo₂C, metallic Ag and vanadium oxide phase. The appearance of metallic Ag and vanadium oxide phase can be attributed to the decomposition of AgVO₃ during sintering. Wear testing results confirmed that NiAl/Mo-based composites have excellent tribological properties over a wide temperature range. For example, the friction coefficient and wear rate of NiAl/Mo-based composites containing AgVO₃ were significantly lower than the composites containing only metallic Mo or AgVO₃ lubricant when the temperature is above 300 °C, which can be attributed to the synergistic lubricating action of metallic Mo and AgVO₃ lubricants. Furthermore, Raman results indicated that the composition on the worn surface of NiAl-based composites was self-adjusted after wear testing at different temperatures. For example, Ag₃VO₄ and Fe₃O₄ lubricants were responsible for the improvement of tribological properties at 500 °C, AgVO₃, Ag₃VO₄ and molybdate for 700 °C, and AgVO₃ and molybdate for 900 °C of NiAl-based composites with the addition of metallic Mo and AgVO₃.     

Ti6Al4V合金激光原位合成自润滑复合涂层高温摩擦学性能

为提高Ti6Al4V合金的高温摩擦学性能,采用激光熔覆技术在其表面原位合成多相混杂金属基高温自润滑耐磨复合涂层,熔覆粉末的成分为Ni60-16.8%TiC-23.2%WS_2(质量分数,下同),系统地研究复合涂层的显微组织、物相结构及其在20,300,600,800℃下的摩擦学性能和相关磨损机理。结果表明:复合涂层的显微硬度(701.88HV_0.5)约为基体(350 HV_0.5)的2倍;由于原位合成固体润滑相(Ti_2SC/TiS/NiS/TiO/TiO_2/NiCr_2O_4/Cr_2O_3)和硬质相(W,Ti)C_1-x/TiC/Cr_7C_3的协同作用,复合涂层的耐磨减摩性能明显优于基体。随着温度升高,涂层和基体的摩擦因数和磨损率均呈下降趋势,在800℃时复合涂层和基体的摩擦因数分别为0.32和0.43,磨损率分别为1.80×10^-4,2.92×10^-5mm/Nm。在800℃下塑性变形、分层和氧化磨损为基体主要磨损机理,复合涂层以氧化磨损和轻微的黏着磨损为主。     

Ag的掺入对MTa2O5多层复合涂层的微观结构、 耐蚀性和抗菌性能的影响

采用磁控溅射技术在Ti6Al4V合金表面制备了含Ag和不含Ag的Ta_2O_5/Ta_2O_5/Ta_2O_5-TiO_2/TiO_2/Ti多层复合涂层(分别用Ag-MTa_2O_5和MTa_2O_5表示),通过SEM、XRD、EDS、纳米压痕仪、电化学工作站和平板计数法,对涂层试样进行表征与检测。研究结果表明,Ag的掺杂对MTa_2O_5多层涂层的结构和性能有重要影响。与MTa_2O_5涂层相比,Ag-MTa_2O_5涂层表面的晶粒变粗、致密度降低、机械性能和耐腐蚀性能略有下降;但Ag-MTa_2O_5涂层的抗菌率为100%,显示出优异的抗菌性能。     

不同含量Ag掺杂对YBa_2Cu_3O_x和Bi_2Sr_2CaCu_2O_x固体自润滑材料摩擦学性能的影响

通过固相反应法制备了YBa2Cu3Ox/Ag和Bi2Sr2CaCu2Or/Ag固体自润滑材料.采用XRD和SEM检测了材料的成分以及相结构.XRD结果表明,所制备的YBa2Cu3Ox/Ag和Bi2Sr2CaCu2Ox/Ag固体自润滑复合材料都是由超导相和Ag相组成.采用销一盘式摩擦试验机研究了试样在常温下的摩擦学性能.结果表明,室温下纯YBa2Cu3Ox的摩擦系数为0.68～0.95,当掺杂15%(质量分数)Ag时,摩擦系数减小到最低,为0.11左右;纯Bi2Sr2CaCu2Ox的摩擦系数为0.21～0.22,当掺杂10%(质量分数)Ag时,摩擦系数降低到最低,为0.18左右.在超导体中添加Ag可有效改善材料的摩擦学性能.Ag可在材料摩擦接触表面形成一层Ag膜,从而有效改善接触表面,达到减小摩擦力的效果.     

不同温度下Fe-Al/Cr3C2复合涂层的摩擦学特性研究

使用THT07-135高温磨损实验机对不同温度下高速火焰喷涂Fe-Al/Cr3C2复合涂层进行滑动摩擦特性研究.运用扫描电镜及能谱仪对磨痕的形貌和不同区域的成分进行观察测试,运用透射电镜对涂层内部硬质相的存在状态进行观察分析.结果表明:高速火焰喷涂Fe-Al/Cr3C2复合涂层具有良好的抗摩擦磨损性能,随着滑动距离的增...     

纳米尺度PS/Ag核壳结构复合球的制备与表征

采用分步法制备了聚苯乙烯/银(PS/Ag)核壳结构复合纳米球。首先采用无皂乳液聚合法并利用丙烯酸(AA)的羧基对制备的PS球进行改性,使其表面带负电荷;然后通过静电吸附作用在改性PS球的表面沉积[Ag(NH3)2]+,水浴(80℃)环境中利用十二烷基磺酸钠(SDS)作为还原剂将PS球表面的[Ag(NH3)2]+还原,制备出PS/Ag核壳结构复合球。通过动态激光粒度分析仪和透射电子显微镜对PS/Ag核壳纳米球的粒度分布、形貌和结构进行了表征,研究了AA的用量对复合球粒径及包覆的Ag壳厚度的影响。结果表明,随着AA用量的增大,所包覆的银层更加致密,厚度增大,当AA用量为15%时可得到Ag完全包覆的PS/Ag复合纳米球。     

激光直接沉积制备Mo-Ni-ZrO_2高温耐磨复合合金梯度涂层

设计30wt%~70wt%不同Mo含量的Mo-Ni混合粉末,通过添加少量ZrO2形成梯度复合合金粉末,采用激光直接沉积技术在3Cr2W8V钢板上制备Mo-Ni-ZrO2高温耐磨复合合金梯度涂层。利用金相显微镜、显微硬度计、SEM、能谱仪及XRD等对制备梯度涂层的组织结构、裂纹与气孔消除、相组成及其硬度等进行了研究。结果表明:在Mo-Ni系复合合金梯度涂层中,由于Mo在激光作用下易氧化为MoO_3,MoO_3受热易挥发,在熔池中未能及时逸出,因此,涂层在50wt%Mo梯度层处开始出现裂纹和气孔,其显微硬度平均值为287.29;在Mo-Ni-ZrO2系梯度涂层中,添加ZrO2后,50wt%Mo梯度层处的裂纹和气孔明显减少,该涂层中主相为MoNi及强化相Mo1.24Ni0.76、Ni3Zr,还有少量MoO_3,其显微硬度平均值为477;ZrO2具有良好的消除Mo-Ni高温复合合金梯度涂层裂纹气孔缺陷与增强梯度涂层硬度的作用。     

坡缕石/Ag复合纳米材料添加剂的自修复性能研究

将坡缕石(Palygorskite,简称P)/Ag复合纳米材料作为润滑油添加剂,以质量分数为4％的添加量添加到150N基础油中作为润滑油,在MMU-10G型摩擦磨损试验机上考察了P/Ag复合纳米材料添加剂对45#调质钢摩擦副的自修复效果.用称重法测定磨损量,用SEM和EDX对最终摩擦表面形貌和表面元素成分进行表征;并用...     

Microstructure, Mechanical and Tribological Properties of Ag/Bi2Sr2CaCu2O x Self-lubricating Composites

Ag/Bi₂Sr₂CaCu₂O _x self-lubricating composites were successfully fabricated by a facile powder metallurgy method. The structure and morphology of the as-synthesized composites and the worn surface after tribometer testing are characterized by using X-ray diffraction and scanning electron microscopy together with energy dispersive spectrometry. The results indicated that self-lubricating composites are composed of superconductor phase and Ag phase. Moreover, the effects of Ag on mechanical and tribological properties of the novel composites were investigated. The friction test results showed that the friction coefficient of the pure Bi2212 against stainless steel is about 0.40 at ambient temperature and abruptly decreases to about 0.17 when the temperature is cooled to 77 K. The friction coefficients of the composites from room temperature to high temperature were lower and more stable than those of pure Bi₂Sr₂CaCu₂O _x . When the content of Ag is 10 wt.%, the Ag/Bi₂Sr₂CaCu₂O _x composites exhibited excellent tribological performance, the improved tribological properties are attributed to the formation of soft metallic Ag films at the contacted zone of the composites.