Qiao Shen

The study of the preparation and tribological behavior of TiAl matrix composites containing 1 wt% multi-walled carbon nanotubes

The objective of searching for an optimized applied load was to minimize friction and decrease energy dissipation in rotating mechanical components. TiAl matrix self-lubricating composites containing 1.0 wt% multi-walled carbon nanotubes (TiAl-1.0 wt% MWCNTs), were evaluated over 80 min on a ball-on-disk tribometer at 1.65, 4.15, 6.65, 9.15 and 11.65 N, for their sliding friction and wear behaviors. The testing results showed that TiAl-1.0 wt% MWCNTs obtained excellent sliding friction and wear behaviors at 9.15 N with small friction coefficients and low wear rates, compared to those at 1.65, 4.15, 6.65 and 11.65 N. It was found that the small mean wear rates of TiAl-1.0 wt% MWCNTs were attributed to the high subsurface hardness of the wear scar. The low standard deviation (STDEV) of the wear rates was mainly determined by the homogeneous thickness of the compacted layer at 9.15 N.

Tribological performance of TiAl matrix composites containing silver and V2O5 nanowires at elevated temperatures

TiAl alloys (TAs) are widely used in aircraft and automotive industries, but their poor wear resistance restrains further applications. In this paper, the tribological properties of TiAl matrix self-lubricating composites containing lubricants of varying amounts (0.5 wt%, 1.5 wt% and 2.5 wt%) of V2O5 nanowires (NWs) and 5 wt% silver against Si3N4 balls were investigated from room temperature to 600 °C under the same conditions of 20 N load per bearing section and 0.35 m s−1 gliding speed. TiAl–5Ag–1.5V2O5 NWs (TB) exhibited excellent tribological properties over a wide temperature range. Moreover, at 450 °C, TB showed a lower friction coefficient of 0.19 and a lower wear rate of 1.87 × 10−4 mm3 N−1 m−1, which were attributed to a continuous lubricating film containing V2O5 NWs and silver on the friction surface. Furthermore, in the formed lubricant films, silver was used as a solid lubricant to provide good lubrication, while V2O5 NWs played the role of a support with high shear strength. The investigation indicated that V2O5 NWs and silver exhibited an excellent synergistic effect for improving the tribological properties of TB.

Effect of elastic and plastic deformations on tribological behavior of graphene-reinforced Ni3Al matrix composites

The elastic and plastic deformations have significant effect on the tribological properties of the graphene-reinforced Ni3Al matrix self-lubricating composites. The primary purpose of this study is to investigate the tribological behavior and wear mechanisms of graphene-reinforced Ni3Al matrix self-lubricating composites by researching the effects of different loads and the corresponding friction heat on the elastic or plastic deformation. The dry sliding tribology tests of graphene-reinforced Ni3Al matrix self-lubricating composites are carried out at the loads of 7, 10, 13, and 16N, respectively. The elastic or plastic deformation is judged by comparing the yield stress with the contact stress analyzed by the numerical simulation method. It is found that graphene-reinforced Ni3Al matrix self-lubricating composites exhibit good tribological properties at 13 N due to the elastic deformation, leading to the formation of relatively stable wear resistant layer. Graphene-reinforced Ni3Al matrix self-lubricating composites show poor tribological performance at 16 N for the plastic deformation, resulting in the destruction of the wear resistant layer and the generation of surface cracks and material spalling. From the mechanical mechanism of wear, the plastic deformation and thermal stress are the important factors to lead to the material spalling. The results could be used to guide the selection of suitable working conditions for having good tribological performance of low wear and long service life.

Effect of MoO3 Tabular Crystals on TiAl Matrix Composites under Different Test Loads

ABSTRACT The friction and wear behavior of TiAl matrix self-lubricating composites (TMSCs) with MoO3 tabular crystals (MTCs) sliding against a GCr15 steel ball is tested using a constant speed of 0.2 m/s at room temperature under different loads from 6.65 to 16.65 N. The result reveals that TMSCs show a consistently lower friction coefficient in a certain range from 0.2 to 0.6 and less wear rate from 0.29 × 10−4 mm3 N−1 m−1 to 0.49 × 10−4 mm3 N−1 m−1 compared to TiAl-based alloy. Moreover, the friction coefficient and wear rate of TMSCs decrease with an increase in test load. MTCs in the deformed layer will be refined to produce interfacial shear slip and reduce the shear stress because of the weak binding force of MTCs in the sliding process, which can facilitate the formation of a deformed layer and protect the deformed layer from spalling failure. In addition, MTCs on the worn surface of TMSCs can reduce the shear stress directly. Hence, MTCs can promote antiwear of the deformed layer and reduce the friction on the worn surface of TMSCs. MTCs can play a better role in antiwear and antifriction when the test load is higher.

Study on the Antifriction and Antiwear Mechanisms of MoO3 Tabular Crystal in TiAl Matrix Composites

In this study, the friction and wear behaviors of TiAl matrix composites with MTC (TMSCT) and TiAl matrix composites with MoO3 powder (TMSCP) are investigated. The results reveal that TMSCT show the excellent tribologcial performance, if compared to TMSCP. The direct contact layers of TMSCP against different counterface balls obtain huge cracks overall, whereas only fine crack is generated in TMSCT against Al2O3 ball, where MTCs are distributed around the crack evenly. The finite element simulations show that only the stress of TMSCT against Al2O3 ball exceeds the yield strength of TMSCT. It reveals that MTCs in TMSCT can reduce the stress for the weak binding force of multilayer structure and make the direct contact layers be more stable by preventing the propagation of crack after the crack being produced, resulting in the excellent antifriction and antiwear properties of TMSCT against different counterface balls.