TiAl Matrix Self-lubricating Composites Research Articles

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

ABSTRACTThe 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.

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

TiAl matrix self-lubricating composites containing 1.0 wt% MWCNTs were evaluated on a ball-on-disk tribometer at 1.65, 4.15, 6.65, 9.15 and 11.65 N for sliding friction and wear behaviors.

Tribological Behavior of TiAl Matrix Composites with MoO3 Tabular Crystal

The friction and wear behaviors of TiAl matrix self-lubricating composites (TMSC) with MoO3 tabular crystal (MTC) against GCr15 steel ball are tested using a constant load of 10 N and a constant speed of 0.2 m/s from room temperature to 600 °C. The result shows that, during the sliding friction and wear process, the MTC which has the microstructure of multiple layers could reduce the shear stress, leading to the reduction of friction coefficient. Meanwhile, TMSC with MTC exhibits the excellent tribological performance over a wide temperature range, if compared to TiAl based alloy. Moreover, MTC can improve the tribological properties of TMSC obviously below 400 °C.

Tribological Properties of TiAl Matrix Self-Lubricating Composites Containing Multilayer Graphene and Ti3SiC2 at High Temperatures

An investigation is conducted on the unexplored synergistic effects of multilayer graphene (MLG) and Ti3SiC2 in self-lubricating composites for use in high-temperature friction and wear applications. The tribological properties of TiAl matrix self-lubricating composites with different solid lubricant additions (Ti3SiC2-MLG, MLG) are investigated from room temperature to 800°C using a rotating ball-on-disk configuration. Tribological results suggest the evolution of lubrication properties of MLG and the excellent synergistic lubricating effect of MLG and Ti3SiC2 as the testing temperature changes. It can be deduced that MLG has great potential applications as a promising high-temperature solid lubricant within 400°C, and a combination of MLG and Ti3SiC2 is an effective way to achieve and maintain desired tribological properties over a wide temperature range.

Formation of Friction Layers in Graphene-Reinforced TiAl Matrix Self-Lubricating Composites

The friction layer structure has been proved to be formed during severe plastic deformation and markedly improves the tribological properties of material. The dry friction and wear performance of graphene-reinforced TiAl matrix self-lubricating composites (GTMSC) at different sliding velocities are systematically researched. GTMSC show the best tribological properties and special friction layer structure containing a wear-induced layer and a grain refinement layer with a nanocrystalline (NC) structure under surface after sliding at a sliding speed of 1.1 m/s. Nanoindentation results show that the grain refinement layer has a higher hardness and elastic modulus than the wear-induced layer. This special microstructure of friction layers beneath the surface after sliding leads to a low coefficient of friction and high wear resistance of GTMSC. Moreover, it is deduced that the appearance of an NC structure results in hardening of the material. The formation mechanisms of friction layers are researched in detail. It can be concluded that the formation of a wear-induced layer results from frictional heat and fracture of the counterpart. The formation of a grain refinement layer is due to severe plastic deformation and dynamic recrystallization. Severe plastic deformation results in the formation of an NC structure and dynamic recrystallization leads to grain refinement.

Wear and friction behaviour of TiAl matrix self-lubricating composites filled with WS2, MoO3 or multilayer graphene

FESEM micrographs of cross-sections of worn surfaces of TiAl matrix self-lubricating composites filled with WS2 (a), MoO3 (b) or multilayer graphene (c).

Tribological behavior of TiAl matrix self-lubricating composites reinforced by multilayer graphene

Anti-friction film with friction-reduction and anti-wear properties is formed under elastic deformation at the von Mises stress of 917 MPa (at 12 N).

Tribological properties of TiAl matrix self-lubricating composites incorporated with tungsten disulfide and zinc oxide

A schematic representation of the self-adjusted action of WS2–ZnO for TWZ at different temperatures.

Effect of TiB2 on Tribological Properties of TiAl Self-lubricating Composites Containing Ag at Elevated Temperature

TiB2 was chosen to further improve the tribological properties of TiAl matrix self-lubricating composites containing Ag. The possible synergetic action of a combination of TiB2 and Ag was investigated using a pin-on-disk high temperature tribometer from room temperature to 600 °C. The tribological test results indicated that the addition of TiB2 obviously enhanced the wear resistance of the composites over a wide temperature range. Moreover, the composites containing TiB2 had a low friction coefficient at 600 °C. The subsurface analysis of cross sections of worn surfaces showed that TiB2 played the role in wear-resistant skeleton and restricted the plastic flow of Ag during dry friction process. The investigation showed that TiB2 and Ag could exhibit good synergistic effect on improving the tribological properties of composites.

Effect of Sliding Speed and Applied Load on Dry Sliding Tribological Performance of TiAl Matrix Self-lubricating Composites

More durable, low-friction self-lubricating materials in modern industry are greatly needed for tribological systems. The current paper presents the tribological performance of TiAl matrix self-lubricating composites (TSC) containing MoS2, hexagonal BN and Ti3SiC2 designated as MhT against GCr15 steel counterface under several sliding speeds from 0.2 to 0.8 m s−1 and applied loads from 6 to 12 N. The results suggested that MhT played an important role in decreasing friction coefficients and wear rates. The covering percentage of transfer layers on worn surfaces varied with the changing of sliding speeds and applied loads, hence resulting in the distinct friction and wear characteristics of TSC. TSC containing 10 wt% MhT exhibited the best excellent tribological performance at 10 N–0.8 m s−1, which could be due to the formation of the best compaction and largest coverage of transfer layer on the worn surfaces.

Wear and Friction of TiAl Matrix Self-Lubricating Composites against Si3N4 in Air at Room and Elevated Temperatures

More durable, low-friction bearing materials over a wide temperature range are needed for turbine components and other high-temperature bearing applications. The current study reported the tribological properties of TiAl matrix self-lubricating composites (TMC) containing MoS2 (a low-temperature lubricant, below 500°C), hBN (a medium-temperature lubricant, below 600°C), and Ti3SiC2 (a high-temperature lubricant, above 600°C) designated as MhT against an Si3N4 counterface at temperatures ranging from 25 to 800°C in air. The load was 10 N and the sliding speed was 0.2 m/s for all tests. Tribological studies indicated that TMC containing MhT showed a lower friction coefficient and wear rate in comparison to TiAl-based alloy at all test temperatures, which was attributed to the excellent synergetic lubricating effect of MoS2, hBN, and Ti3SiC2. TMC containing 5 wt% MhT exhibited the best tribological properties over a wide temperature range.

Friction and Wear Properties of TiAl-Ti3SiC2-MoS2 Composites Prepared by Spark Plasma Sintering

TiAl matrix self-lubricating composites (TMC) with various weight percentages of Ti3SiC2 and MoS2 lubricants were prepared by spark plasma sintering (SPS). The dry sliding tribological behaviors of TMC against an Si3N4 ceramic ball at room temperature were investigated through the determination of friction coefficients and wear rates and the analysis of the morphologies and compositions of wear debris, worn surfaces of TMC, and the Si3N4 ceramic ball. The results indicated that TMC with 10 wt% (Ti3SiC2-MoS2) lubricants had good tribological properties due to the unique stratification subsurface microstructure of the worn surface. The friction coefficient was about 0.57, and the wear rate was 4.22 × 10−4 mm3 (Nm)−1. The main wear mechanisms of TMC with 10 wt% (Ti3SiC2-MoS2) lubricants were abrasive wear, oxidation wear, and delamination of the friction layer. However, the main wear mechanisms of TMC without Ti3SiC2 and MoS2 lubricants were abrasive wear and oxidation wear. The continuous friction layer was not formed on the worn surfaces. The self-lubricating friction layer on the frictional surface, different phase compositions and hardness, as well as density of TMC contributed to the change in the friction coefficient and wear rate.

Effect of Ag and Ti3SiC2 on Tribological Properties of TiAl Matrix Self-lubricating Composites at Room and Increased Temperatures

Dry sliding tribological properties of TiAl matrix self-lubricating composites (TMSC) containing Ag, Ti3SiC2, Ag and Ti3SiC2 were investigated from 25 to 800 °C under ball-on-disk test conditions against Si3N4 counterface under the same conditions of 10 N-0.234 m/s. The results indicated that the tribological properties were strongly dependent on the lubricant additives. TMSC with the addition of Ag and Ti3SiC2 (TAT) exhibited the lower friction coefficients (0.32–0.43) and less wear rates (1.23–4.13 × 10−4 mm3 N−1m−1) in the wide temperature range of 25–800 °C. The excellent tribological properties of TAT over the wide temperature range were attributed to the synergetic effect of Ag and Ti3SiC2 lubricants, silver diffusion forming a rich-silver smooth tribo-film on the frictional surface of TAT at low and moderate temperatures from 25 to 400 °C, while Ti3SiC2 oxidation reaction forming rich-oxide tribo-film on the worn surface of TAT at higher temperatures of 600 and 800 °C.

Tribological performance of TiAl matrix self-lubricating composites containing Ag, Ti3SiC2 and BaF2/CaF2 tested from room temperature to 600 °C

Dry sliding tribological behaviors of TiAl matrix self-lubricating composites (TMSC) containing varying amounts of Ag, Ti3SiC2 and BaF2/CaF2 eutectic (BaF2–38wt.%CaF2) (ATBC) with weight ratio of 1:1:1 against Si3N4 from room temperature (RT) to 600°C at the condition of 10N–0.234m/s were experimentally studied. The results implied that the ATBC could improve friction-reducing and anti-wear ability of TMSC over an extreme range of operating temperatures, which was attributed to the synergetic effect of Ag, Ti3SiC2 and BaF2/CaF2 lubricants. In addition, TMSC containing 9wt.% ATBC exhibited the best tribological properties over the wide temperature range from RT to 600°C.

Tribological behavior of TiAl matrix self-lubricating composites containing silver from 25 to 800 °C

Dry sliding tribological behavior of TiAl matrix self-lubricating composites (TMSCs) containing silver against Si3N4 was investigated from 25 to 800°C at the condition of 10N–0.234m/s. The results indicated that the friction coefficients increased with the increase in test temperature. Moreover, the friction coefficients of TMSC containing silver were lower than that of the base alloy at all the temperatures, which was attributed to the synergetic effect of Ag and Ti2AlC lubricants. TMSC containing 10wt% silver exhibited the best tribological properties over the wide temperature range.