不同润滑条件下氧化铝陶瓷衬板的磨损机制

在干摩擦、水润滑、油润滑3种不同润滑条件下对氧化铝陶瓷进行摩擦磨损试验。利用SEM对磨损后的磨痕进行观察并进行显微组织结构分析,探讨不同介质下氧化铝陶瓷的磨损机制。结果表明:氧化铝陶瓷材料干摩擦条件下的磨损机制为大量的脆性剥落和大量的磨粒磨损,在水润滑条件下为较少的脆性剥落和轻微的磨粒磨损,在油润滑条件下为很少的脆性剥落和极微的磨粒磨损;液体润滑剂可使氧化铝陶瓷材料的磨损量大幅度降低,其中油润滑条件的减磨效果最为突出。     

Influence of Al2O3 reinforcement on the abrasive wear characteristic of Al2O3/PA1010 composite coatings

In the present study, the abrasive wear characteristics of Al₂O₃/PA1010 composite coatings were tested on the turnplate abrasive wear testing machine. Steel 45 (quenched and low-temperature tempered) was used as a reference material. The experimental results showed that when the Al₂O₃ particles have been treated with a silane coupling agent (γ-aminopropyl-triethoxysilane), the abrasive wear resistance of Al₂O₃/PA1010 composite coatings has a good linear relationship with the volume fraction of Al₂O₃ particles in Al₂O₃/PA1010 composite coatings and the linear correlation coefficient is 0.979. Under the experimental conditions, the size of Al₂O₃ particles (40.5-161.0 μm) has little influence on the abrasive wear resistance of Al₂O₃/PA1010 composite coatings. By treating the surface of Al₂O₃ particles with the silane coupling agent, the distribution of Al₂O₃ particles in PA1010 matrix is more homogeneous and the bonding state between Al₂O₃ particles and PA1010 matrix is better. Therefore, the Al₂O₃ particles make the Al₂O₃/PA1010 composite coatings have better abrasive wear resistance than PA1010 coating. The wear resistance of Al₂O₃/PA1010 composite coatings is about 45% compared with that of steel 45.     

Wear properties of two-phase Al2O3/ZrO2 (Y2O3) ceramics at temperatures from 296 to 1073 K

Reciprocating sliding friction experiments were conducted with various two-phase, directionally solidified Al₂O₃/ZrO₂ (Y₂O₃) pins sliding on B₄C flats in air at temperatures of 296, 873, and 1073 K under dry sliding conditions. Results indicate that all the Al₂O₃/ZrO₂ (Y₂O₃) ceramics, from highly Al₂O₃-rich to ZrO₂-rich, exceed the main wear criterion requirement of 10⁻⁶ mm³ N⁻¹ m⁻¹ or lower for effective wear-resistant applications. Particularly, the eutectics and Al₂O₃-rich ceramics showed superior wear properties. The composition and microstructure of Al₂O₃/ZrO₂ (Y₂O₃) ceramics played a dominant role in controlling the wear and friction properties. The controlling mechanism of the ceramic wear, friction, and hardness was an intrinsic effect involving the resistance to shear fracture of heterophase bonding and cohesive bonding and the interlocking microstructures at different scales in the ceramics.     

Dry sliding wear mechanism for P/M austenitic stainless steels and their composites containing Al2O3 and Y2O3 particles

Austenitic stainless steels are used in applications demanding general corrosion resistance at room or moderate operating temperatures. However, their use is often limited by the relative softness of these materials and their suceptibility to wear and galling. The present investigation deals with the dry sliding wear behaviour of two P/M austenitic stainless steels (AISI 304L and 316L) and their composites containing two different ceramic particles (Al₂O₃ and Y₂O₃) and two different sintering activators (BN and B₂Cr). Unlubricated pin-on-disc wear tests were carried out. Wear mechanisms were analysed by means of scanning electron microscopy and X-ray diffraction. A plastic deformation and particle detachment wear mechanism was revealed. Plasticity during sliding induced an austenite to martensite transformation. The presence of ceramic particles (Al₂O₃ and Y₂O₃) and sintering activators (B₂Cr, BN) improved significantly the wear resistance (especially the combination Al₂O₃ and B₂Cr). Ceramic particles limited plastic deformation while sintering activators decreased final porosity.     

Comparison of wear behaviour of plasma-sprayed Al2O3 coatings with and without laser treatment

This paper studies experimentally the effects of CO₂ laser-treatment on the wear behaviour of plasma-sprayed Al₂O₃ coatings, in linear contact sliding (dry, abrasive and lubricated) against SAE 4620 steel. Tests were carried out using a block-on-ring friction and wear tester, under different loads at different speeds. The wear mechanism and the changes in adherence, porosity and microstructure by laser treatment were also investigated. Results show a better wear behaviour for both laser-treated ceramic coating and its paired steel under dry and abrasive conditions, compared with the case without laser treatment. The lubricated wear behaviour of the laser-treated ceramic coating, however, is not improved. The changes in microhardness, porosity and adherence caused by the laser treatment are responsible for the change in wear behaviour of the ceramic coating.     

Sliding wear characteristics of plasma-sprayed Al2O3 and Cr2O3 coatings against copper alloy under severe conditions

Al₂O₃ and Cr₂O₃ coatings were deposited by atmospheric plasma spraying and their tribological properties dry sliding against copper alloy were evaluated using a block-on-ring configuration at room temperature. It was found that the wear resistance of Al₂O₃ coating was superior to that of the Cr₂O₃ coating under the conditions used in the present study. This mainly attributed to its better thermal conductivity of Al₂O₃ coating, which was considered to effectively facilitate the dissipation of tribological heat and alleviate the reduction of hardness due to the accumulated tribological heat. As for the Al₂O₃ coating, the wear mechanism was plastic deformation along with some micro-abrasion and fatigue-induced brittle fracture, while the failure of Cr₂O₃ coating was predominantly the crack propagation-induced detachment of transferred films and splats spallation.     

Modelling particulate erosion–corrosion regime transitions for Al/Al2O3 and Cu/Al2O3 MMCs in aqueous conditions

Very little research effort has been directed at development of models of erosion–corrosion of composite materials. This is because, in part, the understanding of the erosion–corrosion mechanisms of such materials is poor. In addition, although there has been a significant degree of effort in the development of models for erosion of MMCs, there are still difficulties in applying such models to the laboratory trends on erosion rate.In this paper, the methodology for mapping erosion–corrosion processes in aqueous slurries was extended to particulate composites. An inverse rule of mixtures was used for the construction of the erosion model for the particulate MMCs. The corrosion rate calculation was evaluated with reference to the matrix material.The erosion–corrosion maps for composites showed significant dependency on pH and applied potential. In addition, the corrosion resistance of the matrix material was observed to affect the regime boundaries. Materials maps were generated based on the results to show the optimum composite composition for exposure to the environment.     

Study of tribofilms formed during dry sliding of Ta2AlC/Ag or Cr2AlC/Ag composites against Ni-based superalloys and Al2O3

Herein we show that dry sliding, in air, in the 25–550 °C temperature range, of the novel Ta₂AlC/20 vol.% Ag and Cr₂AlC/20 vol.% Ag composites against Ni-based superalloys (SAs) and alumina led to the formation of steady-state tribofilms whose thicknesses and compositions varied depending on sliding conditions. At elevated temperatures, under both isothermal and thermocyclic conditions, relatively thick (>0.5 μm) well-compacted “glaze” lubricious tribofilms were developed as a result of joint action of tribo-chemical and tribo-mechanical factors involving repeated tribo-oxidation, mixing, fracturing, sintering, etc. They were mainly composed of oxidized constituents from both counterparts (if slid vs. SA) or solely from MAX-Ag ones (vs. Al₂O₃) and possessed a fine multi-layered microstructure, i.e. a more oxidized thin outermost layer and a less oxidized carbide-containing thicker inner layer. During thermocycling the tribofilms adapted to 25–550 °C temperature variations and preserved their primary macro- and microstructure, hardness, good adhesion to the matrix and lubricating characteristics. Consequently, the tribological properties of MAX-Ag/SA tribocouples did not deteriorate, but slightly improved with sliding distance. A possible mechanism of tribofilm generation and their transformations at various temperatures is discussed. The effect of SA and alumina counterparts on the formation and degradation of the tribofilms are also discussed.     

Tribological properties of spark-plasma-sintered ZrO2(Y2O3)-CaF2-Ag composites at elevated temperatures

Spark-plasma sintering is employed to synthesize self-lubricating ZrO₂(Y₂O₃) matrix composites with different additives of CaF₂ and Ag as solid lubricants by tailoring the composition and by adjusting the sintering temperature. The friction and wear behavior of ZrO₂(Y₂O₃) matrix composites have been investigated in dry sliding against an alumina ball from room temperature to 800 °C. The effective self-lubrication at different temperatures depends mainly on the content of various solid lubricants in the composites. The addition of 35 wt.% Ag and 30 wt.% CaF₂ in the ZrO₂(Y₂O₃) matrix can promote the formation of a well-covered lubricating film, and effectively reduce the friction and wear over the entire temperature range studied. The friction coefficients at low temperatures were at a minimum value for the composite containing 35 wt.% of silver. At this silver concentration, low and intermediate temperature lubricating properties are greatly improved without affecting high-temperature lubrication by the calcium fluoride in ZrO₂(Y₂O₃) matrix composites. The worn surfaces and transfer films formed during wear process have been characterized to identify the synergistic lubrication behavior of CaF₂ and Ag lubricants at different temperatures.     

High-temperature tribological properties of spark-plasma-sintered Al2O3 composites containing barite-type structure sulfates

Al₂O₃–50BaSO₄–20Ag, Al₂O₃–50BaSO₄–10SiO₂, Al₂O₃–50(mass%)SrSO₄, Al₂O₃–50PbSO₄–5SiO₂, Al₂O₃–50BaSO₄ and Al₂O₃–50BaCrO₄ composites (mass%) were prepared by spark plasma sintering and their microstructure and high-temperature tribological properties were evaluated. Al₂O₃–50BaSO₄–20Ag composites (mass%) showed the lowest friction coefficients at the temperature ranging from 473 to 1073 K. Thin Ag film was observed on the wear tracks of the composites above 473 K. In addition, the friction coefficients of Al₂O₃ composites containing SrSO₄ and PbSO₄ were as low as those of Al₂O₃–BaSO₄ and Al₂O₃–BaCrO₄ composites at the temperatures up to 1073 K. The thin films formed on the wear tracks of the Al₂O₃–SrSO₄ composites were composed of Al₂O₃ and SrSO₄ phases, while the films formed on the wear tracks of the Al₂O₃–PbSO₄–SiO₂ composites consisted of Al₂O₃, PbSO₄ and SiO₂ phases.     

Study on the tribological behavior of hybrid PTFE/cotton fabric composites filled with Sb2O3 and melamine cyanurate

The tribological behavior of the hybrid PTFE/cotton fabric composites filled with microsize Sb₂O₃ and melamine cyanurate (MCA) was investigated. It was found that the wear rate of the hybrid PTFE/cotton fabric composites decreased when Sb₂O₃ was used as the filler but increased with MCA filler. It was also observed that hybrid fillers (consists of Sb₂O₃ and MCA) had a wear reduction effect on the hybrid PTFE/cotton fabric composites at lower loads but increased the wear rate at higher loads. The wear behavior of the composites was explained in terms of the topography of worn surfaces and transfer film formed on the counterpart pin.     

Al2O3/(Ag72Cu28)97Ti3/Ti-6Al-4V界面反应

在1.8 ks、1 073～1 173 K条件下对Al2O3/(Ag72Cu28)97Ti3/Ti-6Al-4V进行了钎焊试验.通过扫描电镜、波谱、能谱和X射线衍射对界面反应产物进行了测试,确定了界面结构,并讨论了这些反应产物形成的可能性.结果表明,温度小于1 123 K的界面结构为Al2O3/Cu2Ti4O/Cu4Ti3+Cu固溶体/Ag-Cu共晶 + 富Ag相;温度1 173 K的界面结构为Al2O3/Cu3TiO5 + CuAl2O4/Cu4Ti3/富Ag相+ Cu4Ti3.     

润滑条件对Al2O3基陶瓷材料摩擦磨损性能的影响

本文对Al2O3基陶瓷材料/45#钢摩擦副的摩擦系数与45#钢/45#钢的摩擦系数作了对比滑动摩擦试验研究,观测分析了Al2O3基陶材料磨痕形貌,并就干摩擦,油润滑状态下Al2O3基陶瓷材料的磨损机理进行了分析。结果表明,分别在干摩擦和20#机油润滑下,Al2O3基陶瓷材料/45#钢的摩擦系数均比45#钢自配副时的低,在干摩擦条件下,Al2O3基陶瓷材料的磨损机理是脆性微剥落和磨粒磨损,油润滑条件下,该材料的磨损机理是脆性脱落和耕犁,但磨损量小于干摩擦条件下的磨损量,说明油润滑对Al2O3基陶瓷材料有明显的减磨作用。     

匀相沉淀法制备纳米Al2O3粉末

介绍了一种以工业用NH4Al(SO4)2*12H2O和NH4HCO3为原料采用匀相沉淀法制备纳米Al2O3粉末的新工艺,并研究了沉淀剂NH4HCO3的滴加速度、醇洗、表面活性剂等因素对Al2O3粒径的影响.研究结果表明,该工艺制备的粉体粒度均匀、平均粒径小于25nm.     

Wear behaviour of AE42+20% saffil Mg-MMC

The wear behaviour of AE42 magnesium alloy and AE42+20% saffil short fibre composite is investigated in dry sliding condition using a pin-on-disc set-up in the load range of 5–40 N with sliding speeds of 0.838, 1.676 and 2.513 m/s for a constant sliding distance of 2.5 km. In case of both the alloy and the composite wear rate increases with increasing loads and the wear rate of the composite is lower at lower loads. At all sliding speeds, a crossover in wear rate is observed with the increase in load, i.e., above a certain load the wear rate of the composite becomes greater than that of the alloy, and the crossover shifts to lower loads with increase in the sliding speed. Severe sub-surface plastic deformation and fibre breakage are found to be the dominant mechanism for the unreinforced alloy and the composite, respectively.     

LOM技术制备Al2O3和BaTiO3陶瓷件

采用轧膜法制备了用于快速成形工艺中的分层实体造型(LOM)技术的Al2O3和BaTiO3陶瓷片坯件,厚度为0.76mm和0.2mm,然后采用LOM技术进行陶瓷零件的成形,脱脂烧结得到最终产物。对陶瓷坯件进行了TG-DTA热分析,对烧结产物进行了SEM微观组织分析,并测定了机械性能。     

采用GPS+HIP生产工艺制造Al2O3基陶瓷刀片

介绍了采用GPS+HIP生产工艺制造Al2O3基陶瓷刀片所涉及的混料、压制、排胶、气氛保护烧结(GPS)、热等静压(HIP)处理、刀片刃磨等主要生产工序。     

Tribological behaviour of Si3N4 and Si3N4-%TiN based composites and multi-layer laminates

Si₃N₄-TiN based multi-layer laminates exhibit differences in residual stress between individual layers due to a variation of the thermal expansion coefficient between the layers. The residual stress distribution in these multi-layer laminates is known to improve the apparent macroscopic fracture toughness. In this work, the tribological behaviour of bulk, composites and multi-layers laminates are investigated. Si₃N₄ bulk, Si₃N₄ based composites with 10, 20 and 30 wt% TiN and different multi-layer laminates have been tested under dry conditions with reciprocal movement using a ball-on-block configuration. In particular, the influence of sliding directions with respect to the layer orientations has been investigated.The experimental results show that wear resistance increased with increasing TiN content in Si₃N₄-TiN composites. However, multi-layer laminates exhibit an up to three times higher apparent fracture toughness, but do not show an improvement of wear resistance compared to composites.     

Effect of reinforcement size and volume fraction on the abrasive wear behaviour of AA7075 Al/SiCp P/M composites—A statistical analysis

In the present study, a new mathematical model was developed to predict the abrasive wear rate of AA7075 aluminum alloy matrix composites reinforced with SiC particles. Five factors, five levels, central composite, rotable design matrix was used to optimise the required number of experiments. The model was developed by response surface method. Analysis of variance technique was applied to check the validity of the model. Student's t-test was utilised to find out the significant factors. The effect of volume percentage of reinforcement, reinforcement size, applied load, sliding speed and abrasive size on abrasive wear behaviour was analysed in detail.