Anisotropic mechanical and tribological properties of SiAlON matrix composites containing different types of GNPs

SiAlONs can have new application areas by increasing their lifetime and durability if their mechanical and tribological properties are improved. Even though the properties of the matrix improve with GNPs addition, the differences in GNPs properties lead to different property values. In this study, four different GNPs having different surface area, lateral dimension, thickness, and aspect ratio were added to SiAlON and composites were sintered by using SPS. The effects of these different properties on fracture toughness and friction coefficient of SiAlONs were investigated. GNPs, which have the high surface area, lateral dimension, aspect ratio and low thickness, provided the highest fracture toughness and best friction coefficient performance to SiAlON. The fracture toughness of composites were generally higher in the in-plane direction compared to through-plane direction due to GNPs orientation. Conversely, the friction coefficient and hardness values measured higher in the through-plane direction than in the in-plane direction.     

Frictional behavior and wear resistance performance of gradient cermet composite tool materials sliding against hard materials

Gradient cermet composites possessing high surface hardness, flexural strength and interface bonding strength were fabricated using vacuum hot-pressing sintering. Ball-on-disk tests were performed to investigate the tribological properties of the gradient cermet composites against 440 C stainless steel, Al₂O₃ and Si₃N₄ balls at different sliding speed and load in comparison with traditional Ti(C,N) cermets. The tribological behavior was characterized in terms of friction coefficient and wear rate. The results showed that friction coefficient was significantly dependent on the sliding speed and load when sliding against Al₂O₃ and Si₃N₄. However, there was no obvious relation between them during sliding against 440 C stainless steel due to the formation of metal adhesive layer. Gradient cermet composites exhibited a higher friction coefficient but lower wear rate than traditional Ti(C,N) cermets. The main wear mechanism of gradient cermet composites was adhesion wear during sliding against 440 C stainless steel, while abrasion wear was the predominant mechanism during sliding against Al₂O₃ and Si₃N₄. It was expected that gradient cermet composites would be excellent candidates for cutting tool materials.     

Wear resistance and hardness properties of TiB2– Fe coating developed on AISI 1020 steel by tungsten inert gas (TIG) cladding

The present work is attempted to improve the microhardness and wear properties of AISI 1020 steel by depositing TiB₂–Fe composite coating using tungsten inert gas (TIG) cladding. In this study, different compositions of TiB₂–Fe paste form were preplaced on the substrate plates and then TIG heat input was applied to deposit hard composite coating layer. The main objective of the present work was to explore the influence of TIG input current as well as iron content on the microstructure and surface properties of deposited coatings. Microhardness, microstructural and phase characterization of the coating have been done by the Vickers microhardness tester, scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS) and X-ray diffractrometer (XRD). The results showed that the microhardness of the TiB₂–Fe coating was strongly influenced by the composition of the coating materials as well as the TIG processing current. The microhardness increases with decreasing Fe contents in the coating materials with constant processing current (90 A) as well as it also increases with decreasing processing current with the fixed composition of coating materials (80TiB₂–20Fe). The maximum average microhardness found was 3082 HV_0.1 for the coating of 100TiB₂–0Fe composition ratio and 90 A processing current which was about 18 times higher than that of the substrate average microhardness value (163 HV_0.1). Average wear rate evaluated by considering weight loss of the TIG cladded samples using pin on disc tribometer by the sliding distance of 864 m and 20 N normal loads. The wear results also showed that the coating contains 100 wt% of TiB₂ (0 wt% of Fe) exhibited lower rate of wear 6.74 × 10^?8 g/Nm which is about 24 times lower as compared to AISI 1020 mild steel wear rate (166.31 × 10^?8 g/Nm).     

The influence of solid lubricant on tribological properties of sintered Ni–20%CaF2 composite material

Powder metallurgy was used in order to produce Ni–20%CaF₂ self-lubricating composite. Ni powder was mixed with 20 wt% of CaF₂ powder. The powder mixture was pressed by the hydraulic press and sintered in the furnace with an inert atmosphere (Ar). Sintering was carried out at temperature of 1200 °C (1473 K) for 2 h. The sintered samples were subjected to wear tests at various temperatures using a pin-on-disc method. SEM and EDS techniques were used to analyze the surface of the samples after the pin-on-disc experiment. During the wear process, the tribofilm was produced on the surface of the composite containing calcium fluoride and caused a decrease in the friction coefficient. Therefore, the composite with CaF₂ addition showed less wear than pure Ni.     

Effect of substrate rotational speed during deposition on the microstructure,mechanical and tribological properties of a-C:Ta coatings

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp² hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating.     

Structure,tribotechnical, and thermophysical characteristics of the fluoroplastic carbonnanotubes material

In this work, we studied a nanocomposite material made from fluoroplastic which contains 20 wt.% multi-walled nanotubes. In order to complete the present work, we have used different thermodynamic and mechanical techniques. The introduction of nanotubes in the F4 polymer matrix has completely changed the tribological and thermodynamic properties of the studied nanocomposite material. The compression strength becomes 20% higher than that of the F4 polymer matrix. Meanwhile the wear resistance achieves an order of magnitude 100 times greaterthan that of F4. Moreover, a friction coefficient is about 25% to 30% lower than that of a similar material and especially that of F4 material. Differential scanning calorimetric study showed that the glassy phase transition appears at about 330°C, which confirms that the degradation of the studied nanocomposite occurs at relatively higher temperature. This result confirms the one concerning the change in tribological properties. Dilatometric study revealed that the thermal expansion coefficient has been increased. The observed relative elongation measurement change depends on the direction along which the measurement has been done and confirms, in turn, the anisotropic character of the studied material. These results suggest that the metallic materials could be replaced by nanocomposite compounds which present good physical properties.     

Friction and wear properties of Si3N4-hBN ceramic composites using different synthetic lubricants

This paper presents a tribological investigation of Si₃N₄-hBN composite ceramics using synthetic lubricants. The friction and wear properties of Si₃N₄-hBN ceramic composites sliding against TC4 titanium alloy (Ti6Al4V) were investigated via pin-on-disc tests. An axial compressive load of 10?N was applied with a sliding speed of 0.73?m/s. Three different lubrication conditions including simulated body fluid (SBF), physiological saline (PS) and bovine serum (BS) were used. For SBF lubrication, the friction coefficients and wear rates of Si₃N₄-hBN/Ti6Al4V pairs were varying with the increase of hBN contents. When using 20?vol% hBN, the average friction coefficient and wear rate of Si₃N₄ (0.28 and 3.5?× 10^?4 mm³ N^?1 m^?1) were as good as that of the pure Si₃N₄ (0.34 and 3.69?× 10^?4 mm³ N^?1 m^?1). Meanwhile, the processability of the Si₃N₄ material would be improved by adding hBN. It was worth to mention that when using 30?vol% hBN, the tribological performance of bearing combination deteriorated with extensive wear from the ceramic pin. This may due to the reduction of mechanical property caused by adding hBN and the occurring of tribochemical reaction. According to the worn surface examination and characterization, the main wear mechanism was abrasive and adhesion wear. Scratch grooves were observed on the metal disc, and metallic transform layers were seen on the ceramic pin. Moreover, surface lubrication film consisting of TiO₂, SiO₂·nH₂O, Mg(OH)₂, and H₃BO₃ were formed on the metal disc when using SBF lubrication and 20?vol% hBN content. Among the three lubrication conditions, SBF generally led to the best tribological performance. No surface lubrication film was found during BS and PS lubrications. This may be resulted from the absence of essential ions to promote the formation of surface lubrication film (PS lubrication) and the formation of a protein barrier on the surface of the metal disc (BS lubrication).     

减磨耐磨聚氨酯复合材料摩擦性能的研究

通过聚醚多元醇与甲苯二异氰酸酯反应，合成了端异氰酸酯基预聚体；在预聚体中加入一些具有减磨功能的添加剂进行物理共混，并用芳香族二胺为固化剂硫化成型，制得减磨耐磨聚氨酯复合材料。着重探讨了不同聚氨酯胶料、减磨添加剂的种类和用量等因素对该复合材料力学性能和耐磨性能的影响。结果表明：聚氨酯胶料的结构不同对弹性体力学性能有不同程度的影响；由相同原料制得的减磨聚氨酯复合材料，硬度越高，磨耗量越小；有机硅类和有机蜡类添加剂与聚氨酯胶料相容性较好，所得的复合材料外观清透，质量损失和体积损失都相对较小，而含氟材料和无机填料添加剂与胶料相容性较差，体系发生明显的相分离；有机硅类添加剂用量宜在０．５％～１．５％范围。     

PPS/PAI/CF复合材料摩擦磨损性能的研究

采用模压成型法制备了聚苯硫醚(PPS)/聚酰胺酰亚胺(PAI)合金及其碳纤维(CF)改性复合材料。测试分析了该复合材料的力学性能,并通过扫描电镜(SEM)对其摩擦磨损表面形貌进行了观察,探讨了复合材料的摩擦磨损性能;考察了PPS/PAI合金的最优配比及CF含量对PPS/PAI/CF复合材料性能的影响。结果表明:PAI的加入改善了PPS的力学性能,当PPS/PAI质量比为40/60时,PPS/PAI合金的力学性能最优;另外,CF的加入使PPS/PAI/CF填充复合材料的摩擦系数和磨损量大幅度下降,其中,当CF含量为30%时,PPS/PAI/CF填充复合材料的摩擦系数和磨损量较未填充PPS/PAI分别下降了66%和90%。     

Mechanical and tribological characterization of deep eutectic solvent assisted electroless Ni–P-hBN coating

Compositions and processing methods govern various characteristic features of electroless coatings. Electroless nickel–phosphorus (Ni–P) composite coatings containing varying amounts of hBN, deposited using a deep eutectic solvent (DES), achieved better tribological properties as compared to the coating of the same composition deposited in the conventional method. This study also attempted to determine the specific concentration of hBN particles in the electroless bath that deposits Ni–P-hBN coating with a superior combination of mechanical and tribological characteristics. Stronger bond formations of hBN particles in the Ni–P alloy matrix ensured by hBN's metallic behavior potentially influence its tribological properties.     

Wear damage of Si3N4-graphene nanocomposites at room and elevated temperatures

Mechanical and tribological properties of nanocomposites with silicon nitride matrix with addition of 1 and 3 wt.% of multilayered graphene (MLG) platelets were studied and compared to monolithic Si₃N₄. The wear behavior was observed by means of the ball-on-disk technique with a silicon nitride ball used as the tribological counterpart at temperatures 25 °C, 300 °C, 500 °C, and 700 °C in dry sliding. Addition of such amounts of MLG did not lower the coefficient of friction. Graphene platelets were integrated into the matrix very strongly and they did not participate in lubricating processes. The best performance at room temperature offers material with 3 wt.% graphene, which has the highest wear resistance. At medium temperatures (300 °C and 500 °C) coefficient of friction of monolithic Si₃N₄ and composite with 1%MLG reduced due to oxidation. Wear resistance at high temperatures significantly decreased, at 700 °C differences between the experimental materials disappeared and severe wear regime dominated in all cases.     

Friction of polystyrene: Consequence on nano-wear

Friction is able to induce major consequences on surface polymer properties (wear, scratch, etc.). These problems are crucial in the case of organic coatings (paints, varnish). The aim of this work is to analyse the influence of friction on the nano-wear behaviour of polystyrene. Studies will be focused on the analysis of the transfer layer induced by the friction of a polystyrene cylinder in contact with a flat and smooth substrate. The model substrate is a hydrophilic silicon wafer (hydroxylated by a piranha treatment). Friction experiments are performed with a translation tribometer which measures the tangential force between the polymer and the substrate for controlled normal force and friction speed. The transfer layer is analysed using atomic force microscopy (AFM). Tentative correlations between transfer layer characteristics and polymer properties are proposed.     

聚苯硫醚在摩擦领域中的应用研究

介绍了聚苯硫醚的特性及其耐磨材料常用的增强添加助剂,特别是对聚苯硫醚在摩擦领域中的近期应用研究进行了详细的综述,并提出了今后研究这类耐磨复合材料应注意的几个问题。     

PEEK复合材料的性能研究

对聚醚醚酮 (PEEK)两种复合材料的物理性能、机械性能和摩擦磨损性能进行了测试 ,并利用扫描电镜 (SEM)对其横断面和磨痕表面进行了分析。结果表明 ,灰色PEEK复合材料的摩擦系数为 0 18,比磨损率为 1 79× 10 -6mm3 /(N·m) ;黑色PEEK复合材料的摩擦系数为 0 2 1,比磨损率为 0 61× 10 -6mm3 /(N·m) ,两种复合材料主要受粘着磨损机制控制 ,并伴有热塑性流动磨损     

纤维增强聚苯硫醚复合材料摩擦磨损性能的研究

分别以玻璃纤维(GF)与碳纤维(CF)作为增强体制备了聚苯硫醚(PPS)纤维增强复合材料。研究了GF/PPS和CF/PPS复合材料的摩擦磨损性能,以及不同体积分数的纤维增强体、不同载荷与滑动速度对复合材料的摩擦磨损性能的影响。结果表明:GF与CF的引入有效地提高了复合材料的摩擦磨损性能;随纤维体积分数的增加复合材料的摩擦系数逐渐增加,随载荷的增加复合材料的摩擦系数逐渐降低,但磨损率增大。     

Influence of Re-adhesion on the Wear and Friction of Glass Fibre–Reinforced Polyester Composites

Based on the well-known pin-on-disc test rig, a new test setup for online measuring of wear and friction behaviour of polymer matrix composites has been developed. In contrast to a traditional friction-and-wear test rig, a steel pin and composite disc are used for studying the influence of wear debris and fibre orientation. During sliding, a thin adhesive film is possibly formed on the wear track of a composite disc, consisting of wear debris that is squeezed under the steel pin and that finally smoothens onto the composite surface. By optical microscopy, it was observed that most of the debris particles originate from the edges of the wear track. The thin film deforms continuously, with large and dark wear particles observed at the edge of the wear track. A lower coefficient of friction is achieved when the particles are re-adhered to the mating surface. The film formation mechanism depends on the normal force, sliding velocity, and bulk composite structure: because pultruded composite profiles are presently used with a layered structure, a change in film properties is observed depending on the wear depth.     

Influence of Re-adhesion on the Wear and Friction of Glass Fibre-Reinforced Polyester Composites

Based on the well-known pin-on-disc test rig, a new test setup for online measuring of wear and friction behaviour of polymer matrix composites has been developed. In contrast to a traditional friction-and-wear test rig, a steel pin and composite disc are used for studying the influence of wear debris and fibre orientation. During sliding, a thin adhesive film is possibly formed on the wear track of a composite disc, consisting of wear debris that is squeezed under the steel pin and that finally smoothens onto the composite surface. By optical microscopy, it was observed that most of the debris particles originate from the edges of the wear track. The thin film deforms continuously, with large and dark wear particles observed at the edge of the wear track. A lower coefficient of friction is achieved when the particles are re-adhered to the mating surface. The film formation mechanism depends on the normal force, sliding velocity, and bulk composite structure: because pultruded composite profiles are presently used with a layered structure, a change in film properties is observed depending on the wear depth.