In this study, the microstructure, high-temperature tribological performance, and mechanical properties of solution-aged Ti–10V–2Fe–3Al were investigated. The microstructure of solution-aged Ti–10V–2Fe–3Al reveals a bimodal α and β microstructure with uniformly dispersed α precipitates in the β matrix phase. The hot tribological performance of solution-aged Ti–10V–2Fe–3Al was investigated at different temperatures (28, 250, 350, and 450 °C) in a high-temperature pin-on-disc configuration. The wear mechanisms were evaluated at the worn-out surface using a scanning electron microscope (SEM). The abrasive wear mechanism is predominant at 28 °C and 250 °C testing conditions, whereas the oxidation and delamination are dominant wear mechanisms at 350 °C and 450 °C testing conditions. The worn-out surface at different temperature conditions was characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectrometer (EDS) analysis. The absence of protective oxide formation at 28 °C and intermittent protective oxide formation at 250 °C testing condition are ineffective in protecting the surface from wear damages and high wear loss. The protective tribo-oxide formations at 350 °C and 450 °C are continuous and provide improved wear resistance behavior of the material. The V 2 O 5 -rich tribo-oxide layer formation at 350 °C offers excellent wear resistance and protection against wear damages among the testing conditions. The Vickers microhardness study of the samples tested at different temperature conditions shows significant differences in the hardness magnitude at the cross section.

In this study, the Mo-alloyed HfN films were prepared by DC-magnetron sputtering and studied their tribological properties at 25–600 °C under dry friction conditions. The relationship between H/E value and tribological properties at elevated temperature was illustrated. A single solid-solution phase was formed for all Hf-Mo-N films which with an FCC structure, and the H/E and H 3 /E 2 values are increased. The film with x = 0.56 obtained a lower friction coefficient (0.4) and wear-rate (1.23 × 10 −6 mm 3 /N m) at room temperature. At elevated temperature, this film maintained high structure stability, meanwhile, a dense and continuous oxide layer with lubrication was formed and tightly covered on the worn surface, that it obtained a lower coefficients of friction and better wear resistance.

The aim of this study was to investigate the effect of low-temperature aluminizing process on the microstructure and dry sliding wear properties of Mirrax steel. Low-temperature aluminizing process was applied on Mirrax steel at 600, 650, and 700 °C for 2, 4, and 6 h. The packs for the process were prepared using pure aluminum powder as aluminum deposition source. Ammonium chloride NH 4 Cl and Seydisehir Al 2 O 3 powder were used as the activator and the inert filler, respectively. Scanning electron microscope (SEM)/energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis were applied for characterization of the coating surfaces. The through-thickness variation in the layer microstructure was determined and it was found to vary between 1 µm and 45 µm which increased with higher process temperature and time. After the deposition process, the coating layer hardness increased to 1000 HVN, whereas the hardness of the matrix was 250 HVN. The wear tests were performed using a ball-on-disc tribometer under 5 N load at room temperature and 500 °C on aluminized and untreated Mirrax steel. In both room temperature and high-temperature wear tests, it was determined that the aluminizing process increased the wear resistance of Mirrax steel. Increasing aluminizing time and temperature also increased the wear resistance. The uncoated and thin-coated samples generally exhibited wear in the form of plastic deformation and adhesion related ruptures. A high degree of tribological layer was observed on the wear trace on samples with high coating thickness, especially in high-temperature tests. Therefore, the volume losses in these samples were induced by fatigue crack formation and delamination.

In this study, high-temperature wear performance of A356+Gr-ZrO 2 aluminum matrix composites (AMCs) produced by the mechanochemical reaction method was investigated. After the aluminum composite powders were cold-pressed (750 MPa), the green compacts were sintered under 10 −6 mbar vacuum for an hour at 550 °C. Sintered AMCs have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness and density measurements. Wear tests were conducted in two different loads (10 N and 30 N), five different temperatures, and three different sliding distances in the standard pin-on-disc type wear tester. Result showed that ZrO 2 added to the matrix tends to cluster in grain boundaries. AMCs hardness and densities increased with the increasing amount of reinforcement, and the highest hardness and density value was obtained with 12% ZrO 2 -added AMCs. Weight loss increased with increasing load and temperature and decreased with increasing amount of reinforcement in the matrix at all loads and temperatures.

AISI 316 austenitic steel is extensively used in various components of power plants like boilers, boiler tubes and pipes, which suffer severe air jet erosion. Fly ash is a major erodent in that case. Present study is conducted to study the effect of Cr 3 C 2 25 (Ni20Cr) coating on 316 substrates, when it is exposed to thermal power plant erosive conditions. High-velocity oxy-fuel deposition technique is used for coating. Major constituent of Indian fly ash is alumina, so alumina particles are taken as erodent. Erosion wear behavior is investigated for coated and uncoated conditions using an air jet erosion tester at 100 m/s impact velocity. Three impact angles, i.e., 30 deg, 60 deg, and 90 deg, and four working temperatures, room temperature, 200 °C, 400 °C, and 600 °C, were chosen to identify wear mechanism. Scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX) were utilized to characterize the coated, uncoated, and eroded surface. Erosion behavior is correlated with micro hardness, roughness, and microstructure. Results reveal that the coated surface offers better erosion resistance than the uncoated surface. Substrate exhibits ductile wear behavior as it shows higher wear rate at low angle and decreases on increasing the impact angle, while coating offers good wear characteristics at 30 deg and 90 deg impact angles. An increase in working temperature favors wear rate increment for both coated and uncoated samples. However, coated samples exhibit ductile erosive behavior at high temperatures. Uncoated surfaces have micro-cutting and deformation as major erosive mechanisms. Whereas for coated samples at high temperature, oxide layer formation takes place and erosion takes place due to spalling of the oxides from the coated surface.

Nowadays, the titanium alloys observe broad applicability in aerospace, marine, automobile, and bio-medical industries due to their lightweight, bio-compatibility, good fatigue strength, and corrosion resistance. However, it possesses poor tribological behavior characterized by a high coefficient of friction (CoF) and the specific wear rate (SWR). In this paper, the impact of the electrical discharge machining on the tribological properties of Ti6Al4V (Ti64) was compared before and after electrical discharge machining (EDM) using a pin-on-disk tribometer under un-lubricated and ambient temperature. Besides, ex-situ analysis was performed on the distinct pin surfaces using (i) scanning electron microscopy (SEM), (ii) energy-dispersive X-ray spectroscopy (EDX), and (iii) X-ray diffraction spectroscopy (XRD) techniques to elucidate the associated wear mechanisms. The mechanical properties such as nano-hardness and elastic modulus of the test surfaces were also determined using a nano-indenter. Significant improvement in SWR (65.44% reduction) with a passable compromise for CoF (22.5% increment) occurred during experimentation (before and after EDM) at 100 N. Besides, the wear behavior of the electrical discharge alloyed Ti64 (ETi64) was evaluated at 200 °C, 400 °C, and 600 °C under the applied loads of 50–150 N. At 400 °C and 600 °C, the SWR initially decreased and then increased with variation in load from 50–100 N and 100–150 N, respectively. The enhanced tribo-behavior at 100 N was due to the protective influence of tribo-oxides, viz., TiO 2 and Ti 8 O 15 assisted by the hard Ti 24 C 15 carbides in the recast layer (RL).

SrSO 4 ceramic was prepared by hot-pressed sintering and its friction behavior was investigated against the Al 2 O 3 ball under the dry sliding condition from room temperature to 800 °C. From room temperature to 400 °C, the tribological properties of SrSO 4 ceramic are quite poor with the friction coefficients of 0.65–0.83 and the wear rates of about 10 −3 mm 3 /Nm. With the testing temperature increasing to 600 °C and 800 °C, a brittle to ductile transition of SrSO 4 takes place because of the activated slip systems. The friction coefficient and wear rate of SrSO 4 ceramic also obviously decrease to 0.37 and about 10 −4 mm 3 /Nm at 800 °C. The significant improvement of the tribological properties is ascribed to the formation of a smooth and continuous SrSO 4 lubricating film with excellent ductility and low shear strength at elevated temperature. SrSO 4 is considered to be a potential candidate for high-temperature solid lubricant with excellent lubricity.

The synergistic effect of solid lubricants plays a significant role in wide-temperature-range lubrication, where the combination of lubricious oxide and Ag is the promising solid lubricants. In this paper, the friction and wear performances of Ni 3 Al with the addition of Ag and V 2 O 5 solid-lubricating composites were evaluated from room temperature to 1000 °C. It was found that Ni 3 Al matrix composite with the addition of V 2 O 5 has high friction coefficient of 0.3–0.7, while Ni 3 Al matrix composite with simultaneous addition of Ag and 2 wt % V 2 O 5 has a relatively low friction coefficient of 0.25–0.4 between room temperature and 1000 °C and wear rate with the magnitude of 10 −5 mm 3 /N m at high temperatures. The results revealed that nickel aluminum matrix solid-lubricating composite lubricated by silver and in situ formed silver vanadate at elevated temperature achieves a wide-temperature-range lubrication, which is attributed to the synergistic action of silver and silver vanadate formed at high temperatures.

In this work, layered ternary Cr 2 AlC powders with high purity and a size of 0.5–1 μ m were synthesized by solid-state reaction method. NiCr–Cr 2 AlC composites have been prepared by spark plasma sintering (SPS) process. The composites' tribological properties were evaluated against alumina ball under dry sliding condition from room temperature to 600 °C. Compared with unmodified NiCr alloy, Cr 2 AlC addition has an effect on reduction of friction coefficient of NiCr–Cr 2 AlC composites at the temperatures up to 400 °C. Especially, in comparison with NiCr alloy, the wear rates of NiCr–Cr 2 AlC composites significantly decrease from 10 −4 mm 3 /(N·m) to 10 −5 –10 −6 mm 3 /(N·m) from room temperature to 600 °C (except for 200 °C). The NiCr–20 wt % Cr 2 AlC composite exhibited excellent tribological properties with a friction coefficient of 0.3–0.4 and a wear rate of about 10 −6 mm 3 /(N·m) from 400 °C to 600 °C. Through the analysis of scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS), it is clarified that effective improvement of tribological properties of NiCr–Cr 2 AlC composites is attributed to a glaze layer consisting of NiO, Cr 2 O 3 , Al 2 O 3 , and NiCr 2 O 4 , which is formed by tribo-oxidation during wear process.

The present work was primarily conducted to study the wear behavior of as-received and severely deformed Al-15%Mg 2 Si in situ composites. The severe plastic deformation was applied using accumulative back extrusion (ABE) technique (one and three passes). The continuous dynamic recrystallization (CDRX) was recognized as the main strain accommodation and grain refinement mechanism within aluminum matrix during ABE cycles. To investigate the wear properties of the processed material, the dry sliding wear tests were carried out on both the as-received and processed samples under normal load of 10 and 20 N at room temperature, 100 °C, and 200 °C. The results indicated a better wear resistance of processed specimens in comparison to the as-received ones at room temperature. In addition, the wear performance was improved as the ABE pass numbers increased. These were related to the presence of oxide tribolayer. At 100 °C, the as-received material exhibited a better wear performance compared to the processed material; this was attributed to the formation of a work-hardened layer on the worn surface. At 200 °C, both the as-received and processed composites experienced a severe wear condition. In general, elevating the temperature changed the dominant wear mechanism from oxidation and delamination at room temperature to severe adhesion and plastic deformation at 200 °C.

TiAlN and TiSiN coatings were deposited on YT15 cemented carbide using a cathodic arc ion plating (CAIP). The surface-cross section morphologies, chemical elements, surface roughness, phases, and chemical valences of as-obtained coatings were analyzed using a scanning electron microscopy (SEM), energy dispersive spectroscopy, atomic force microscopy (AFM), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS), respectively, and the bonding strength, hardness and Young's modulus of TiAlN and TiSiN coatings were measured using a scratch tester and nano-indentation, respectively, and the wear mechanism at high temperatures was also discussed. The results show that the surface roughness of TiAlN and TiSiN coatings is 69.1 and 58.0 nm, respectively, and the corresponding average particle size is 998.8 and 817.2 nm, respectively. The TiAlN coating is composed of TiAlN and AlN, while the TiSiN coating is composed of TiN and Si 3 N 4 . The bonding strength of TiAlN and TiSiN coatings is 84.3 and 72.6 N, respectively, the hardness and Young's modulus of TiAlN coating is 23.67 and 415.80 GPa, respectively, while that of TiSiN coating is 20.46 and 350.40 GPa, respectively. The average coefficients of friction (COFs) of TiAlN and TiSiN coatings are 0.4516 and 0.4807, respectively; the corresponding wear rate is 589.7 × 10 −6 and 4142.2 × 10 −6 mm 3 N −1 s −1 , respectively; the wear mechanism of TiAlN and TiSiN coatings is oxidation wear and abrasive wear.

Wear-resistant aluminum alloys have enormous potential applications. In this paper, the Al–20Si–5Fe–2Ni alloy was fabricated by hot-pressed sintering, and its dry sliding wear behavior was investigated from 25 °C to 500 °C sliding against Al 2 O 3 ceramic and AISI 52100 steel. The microstructure, phase, high temperature hardness, and worn surface of the sintered alloy were examined. The results indicate that the uniform distribution of Si particles and Al 5 FeSi intermetallic in the Al matrix contribute to its superior tribological properties. Additionally, the correlation of the tribological behavior of the alloy with the sliding testing conditions was studied, and its wear mechanism was discussed.

This study reviews the work performed in the field of reciprocating shaft seals from the advent of the scientific topic in the 1940s. Concepts of leakage, film layers, friction, wear, and other concerns with shaft seals are discussed. The importance of shaft seals as it pertains to liquid springs is brought to light along with issues requiring a need for these seals to withstand high temperatures and high pressures. Issues resulting from a seal exposure to high temperatures, such as thermosetting and embrittlement, are discussed in conjunction with materials and properties that allow seals to operate in high-temperature environments. High-pressure sealing challenges are identified along with the techniques currently employed to overcome these issues, such as fiber reinforcement and backup rings. Sealing solutions have been implemented independently for both high-pressure and high-temperature applications; however, the combination of high pressures coupled with high temperatures is still a challenge today.

A chromium nitride (CrN) coating was deposited on YT14 cemented carbide using a cathodic arc ion plating (CAIP). The high temperature friction and wear of the obtained coating were investigated using a wear test. The results show that the Cr and N form the atom-rich zones in the coating. The average coefficient of friction (COF) of CrN coatings at 300 °C, 400 °C, and 500 °C is 0.50, 0.62, and 0.43, respectively. The wear mechanism of CrN coating at 300 °C and 400 °C is abrasive wear, and that at 500 °C is abrasive wear, accompanied by slight oxidation wear.

Tribological and mechanical properties of aramid fiber (AF), graphite (Gr), and hexagonal boron nitride (h-BN) hybrid polyimide composites were investigated under room and high temperature. Results show that, Gr in composite reinforced with AF and h-BN can reduce coefficient of friction (COF) and improve antiwear property of composites under room temperature. Gr can accelerate the formation of transfer film under high temperature without sacrificing the wear resistant of composites. Transfer film of composites reinforced with Gr and h-BN simultaneously present more smooth and uniform compared with that of composites reinforced with only AF and h-BN. However, under higher temperature, composite reinforced with pure Gr present higher COFs and wear rates (WRs) compared with composites filled with h-BN and Gr simultaneously. Comprehensively, composite filled with 10% AF, 3% h-BN, and 4% Gr is the optimum composition.

AA5052/ZrB 2 particulate aluminum matrix composites (PAMCs) have been produced by in situ reaction of K 2 ZrF 6 and KBF 4 compounds with molten alloy at about 860 °C. Dry sliding wear and friction of composites have been investigated for a particular sliding velocity and sliding distance at different loads from ambient temperature to 200 °C. It is revealed that for a particular load and temperature, wear rate and normalized wear rate decrease with increase in the volume percentage of ZrB 2 particles whereas coefficient of friction (COF) shows a reverse trend. Wear rate and COF also increase with increase in temperature for a constant load and composition. Whereas with load for a particular temperature, wear rate and wear rate per unit vol. % ZrB 2 increase while COF decreases. Worn surface and wear debris morphology examined under scanning electron microscopy (SEM) and profilometer to understand the wear mechanism revealed that wear mode transition takes place from mild-oxidative to severe-metallic at 100 °C for unreinforced alloy, whereas a shifting is observed in transition temperature from 100 to 150 °C for composite with 9 vol. % ZrB 2 particles. Energy dispersive spectroscopy (EDS) analysis of worn surface confirms the oxidative wear mode. Profilometry results indicate that wear surface has higher surface roughness at higher values of load and temperatures. Prior to wear and friction studies, composites were also characterized by X-ray diffraction (XRD) and SEM for morphology and microstructural characteristics to correlate with wear results. The findings are very helpful to make the AA5052/ZrB 2 composites suitable for the applications, where high-temperature wear is a limiting factor.

High temperature self-lubricating NiAl matrix composites with addition of CuO (15, 20, and 25 wt.%) were fabricated by powder metallurgy technique, and the tribological behavior from room temperature to 1000 °C was investigated. It was found that Ni–Cu and Al 2 O 3 phases formed during the fabrication process due to reaction of NiAl and CuO. The tribological results showed that the composite with addition of 25 wt.% CuO has a favorable friction coefficient of about 0.2 and excellent wear resistance with the magnitude of 10 −6 mm 3 N −1 m −1 at high temperatures (800 and 1000 °C).

A combination technology of the solid lubricant and the laser surface texturing (LST) can significantly improve the tribological properties of friction pairs. The plate sample was textured by fiber laser and composite lubricant of polyimide (PI) and molybdenum disulfide (MoS 2 ) powders were filled in the microdimples. Sliding friction performances of micron-sized composite lubricant and nano-sized composite lubricant were investigated by ring-plate tribometer at temperatures ranging from room temperature (RT) to 400 °C. On the one hand, the results of the micron-sized composite lubricant show that the friction coefficient of the textured surface filled with composite lubricant (TS) exhibits the lowest level and the highest stability compared to a textured surface without solid lubrication, smooth surface without lubrication, smooth surface burnished with a layer of composite solid lubricant. The better dimple density range is 35–46%. The friction coefficients of the sample surface filled with micron-composite solid lubricant with the texture density of 35% are maintained at a low level (about 0.1) at temperatures ranging from RT to 300 °C. On the other hand, the results of the nano-sized composite lubricant show that these friction properties are better than those of MoS 2 -PI micron-sized composite. The friction coefficients of MoS 2 -PI-CNTs nano-sized composite solid lubricant are lower than those of the MoS 2 -PI composite lubricant at temperatures ranging from RT to 400 °C. In addition, the possible mechanisms involving the synergetic effect of the surface texture and the solid lubricant are discussed in the present work.

Self-lubricating composite NiAl–Cr–Mo–CaF2–Ag was fabricated by powder metallurgy technique. The NiAl matrix composite with 10 wt.% Ag provides self-lubricating properties at a broad temperature range between room temperature and 1000 °C. Especially at 800 °C, the composite offers excellent friction reduction about 0.2 and wear resistance about 0.7 × 10−4 mm3 N−1 m−1. The lubricous behavior at a wide temperature range could be attributed to the synergistic effect of Ag, CaF2, CaCrO4, and CaMoO4.