Yuchun Huang

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.

Study on Tribological Performance of NiAl Matrix Self-Lubricating Composites Containing Graphene at Different Loads

ABSTRACT This study aimed to explore the possibility of improving the tribological performance of NiAl matrix composites by graphene addition. Friction and wear experiments of as-prepared specimens were conducted under different conditions using a pin-on-disk wear testing machine. NiAl matrix composites containing graphene showed satisfactory performance in friction coefficient and wear resistance compared to NiAl matrix composites without graphene. For the active effect of graphene, the friction coefficient and wear rate of NiAl matrix composites were maintained at relatively lower values. The beneficial antifriction and antiwear effects of graphene gradually failed when the applied load was above 8 N. Graphene in NiAl matrix composites played an active role in the formation of a friction layer, which was beneficial to the lower friction coefficient and wear rate. In light of this research, graphene plays an active role in reducing the friction coefficient and wear rate. Hence, graphene has great potential in applications as an effective solid lubricant to promote tribological behavior.

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.

Microstructure and Functional Mechanism of Friction Layer in Ni3Al Matrix Composites with Graphene Nanoplatelets

Microstructure and functional mechanism of friction layer need to be further researched. In the present work, the friction coefficients and wear rates are analyzed through response surface methodology to obtain an empirical model for the best response. Fitting results show that the tribological performance of Ni3Al matrix composites (NMCs) with graphene nanoplatelets (GNPs) is better than that of NMCs without GNPs, especially at high sliding velocities and high loads. Further research suggests that the formation of integrated friction layer, which consists of a soft microfilm on a hard coating, is the major reason to cause the differences. Of which, the wear debris layer (WDL) with a low shear strength can reduce the shear force. The ultrafine layer (UL), which is much harder and finer, can effectively avoid fracture and improve the load support capacity. Moreover, the GNPs in WDL and UL can be easily sheared and help to withstand the loads, trending to be parallel to the direction of shear force.

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.

A study of the friction layer of TiAl-10 wt.% Ag composite and the prediction model of friction and wear behaviors:

It was significant to study the longevity of mechanical component by analyzing the effect of friction layer on the predicting models of wear rates and friction coefficients. In this study, based on the changes in applied load F and testing temperature T, the friction and wear behaviors of TiAl-10 wt.% Ag were carried out sliding against Si3N4 ball (6 mm in diameter). At 0–80 min, the prediction models of friction coefficients and wear rates were constructed by the method of bivariate rational interpolation. The predicting accuracies of Pcomp-f: 94–98.7% (friction coefficient) and Pcomp-w: 87.7–98.5% (wear rate) indicated that the constructed prediction model was able to evaluate the friction coefficients and wear rates of TiAl-10 wt.% Ag. The high predicting accuracies were mainly attributed to the excellent plastic fluidity of silver, the smooth morphology of wear scar, and the friction layer of low grain strain.

Effects of frictional heat on the tribological properties of Ni3Al matrix self-lubricating composite containing graphene nanoplatelets under different loads

In order to analyze the effects of frictional heat on the tribological performance of Ni3Al matrix self-lubricating composite containing 6.2 vol.% graphene nanoplatelets (NB), the dry sliding friction tests of Ni3Al-based alloy and NB against GCr15 steel ball are undertaken under different loads from 3 to 18 N. The effects of different amount of frictional heat on the friction and wear mechanism of NB are also studied. The results show that tribological performance of NB is better than that of Ni3Al-based alloy under same working conditions. The addition of graphene nanoplatelets promotes the formation of stable glaze layer on worn surface. In addition, graphene nanoplatelets enhance the thermal conductivity of NB, which makes the surface temperature of wear scar of NB in a proper range (about 413 ℃) at 13 N and avoids the serious friction and wear caused by the accumulation of frictional heat. At 13 N, NB shows the lower friction coefficient (0.32) and wear rate (3.6 × 10−5 mm3·N−1·m−1). It is attributed to the appropriate local temperature (about 413 ℃) of worn surface, resulting in the formation of stable glaze layer with good friction reducing and wear resistance on worn surface. This study was meaningful for optimizing applied loads to realize the appropriate frictional heat and good tribological behavior of NB.

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.