High Temperature Tribometer Research Articles

Thermal Stability and High-Temperature Super Low Friction of γ-Fe2O3@SiO2 Nanocomposite Coatings on Steel

The thermal stability of the γ-Fe2O3@SiO2 nanocomposites and super low friction of the γ-Fe2O3@SiO2 nanocomposite coatings in ambient air at high temperature are investigated in this paper. X-ray diffraction, scanning electron microcopy, transmission scanning electron microcopy, high-temperature tribometer, thermogravimetric analysis and differential scanning calorimetry were used to investigate the microstructure, surface morphology and high-temperature tribological properties of the γ-Fe2O3@SiO2 nanocomposite coatings, respectively. The results show that the γ-Fe2O3@SiO2 nanocomposite with the core–shell structure has excellent thermal stability because the SiO2 shell inhibits the phase transition of the γ-Fe2O3 phase to the α-Fe2O3 phase in the nanocomposites. The temperature of the phase transition in γ-Fe2O3 can be increased from 460 to 829 °C. The γ-Fe2O3@SiO2 nanocomposite coatings exhibit super low friction (0.05) at 500 °C. A high-temperature super low friction mechanism is attributed to γ-Fe2O3 and the tribochemical reactions during sliding.

Investigation of the friction and wear characteristics of polycrystalline diamond compact in a wide temperature range

The friction and wear behaviours of polycrystalline diamond compact (PDC) at temperatures ranging from room temperature to 600 °C are evaluated using a pin-on-disc high-temperature tribometer, and the microstructures and chemical compositions of the worn PDC surfaces are analysed experimentally. The results show that the friction coefficient of PDC is significantly affected by temperature; the friction coefficient decreases with increasing temperature below 200 °C and increases with increasing temperature above 200 °C; the friction coefficient is the lowest at 200 °C, with a value of 0.048. The fluctuation of the friction coefficient with temperature is related to the different synthesis results of surface deformations and tribochemical reactions during the sliding tests at different temperatures. The exfoliation of the diamond grains and Co phase from the PDC surface results in a scratched appearance on the PDC surface, which has a friction-increasing effect and dominates at temperatures above 200 °C. The cobalt oxides and graphite formed on the PDC surface can operate as solid lubricants to decrease the interfacial friction of the PDC, which has a friction-decreasing effect and dominates at temperatures below 200 °C.

PVD coating strategies: Developing a combination of AlCrN and AlTiSiN for enhanced surface performance during threading of super duplex stainless steel

Super duplex stainless steel (SDSS) is one of the difficult-to-machine materials due to its high tendency to work-harden and low thermal conductivity. According to recent findings, PVD hard coatings based on Al, Cr, and Ti are recommended for SDSS machining. In this work, three different PVD coating systems were applied for the threading process of SDSS. Monolayer Al50Cr50N, Al60Cr40N, and multilayer Al60Cr40N/Al50Ti45Si5N were deposited on cemented carbide inserts. This paper highlighted the effect of alloying and coating architecture design on the cutting tools' mechanical properties, tribological characteristics, and wear performance. A novel balanced combination of AlCrN/AlTiSiN multilayer coating with a Si content of 5 at. % was proposed, and it exhibited improved adhesion, beneficial mechanical properties, and superior cutting tool life. Furthermore, tribological characteristics under extreme environments were analyzed through a heavy-load, high-temperature tribometer, as well as XPS and AES measurements. The surface integrity of workpiece material machined by various coatings was also examined through microstructure, microhardness, and residual stress measurements. The depth profiles of residual stress reveal that the machining process significantly impacts the outcome, influenced by the tribological properties of the coatings. Specifically, the AlCrN/AlTiSiN coating exhibits a minimal effect on the surface. These investigations enhance the comprehension of the mechanisms that cause material mechanical surface transformation in threading operations, contributing to a deeper understanding of machining processes.

High-Temperature Wear and Frictional Performance of Plasma-Nitrided AISI H13 Die Steel

Plasma nitriding, a surface treatment technique, is gaining popularity, as it is environment-friendly and offers superior mechanical properties. This research studied the wear and friction performance of AISI H13 die steel after plasma nitriding in a gas mixture of N2:H2 at 20:80, 50:50, and 80:20 (volume ratio) at a fixed time and temperature. This work aimed to analyze the sliding wear performance of the plasma-nitrided tool die steel in hot-forming operations at higher loads. Scanning electron microscopy/electron-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) techniques were used to study the microstructures of the H13 die steel pins after plasma nitriding. Wear tests were performed on a high-temperature tribometer under uni-directional sliding and dry conditions using a high-temperature tribometer under a 50 N load at various operating temperatures ranging from 25 °C to 600 °C. The results show that the plasma-nitriding process with N2:H2 at 20:80 improved the wear behavior of H13 steel. The friction coefficients and wear volume losses for all the plasma-nitrided specimens were less than those of the untreated die steel.

Wear behavior and wear mechanism of iron foam reinforced SiCp/A359 interpenetrating phases composites at high temperature

The A359-SiCp/Fe interpenetrating phase composites reinforced with three-dimensional network structure iron foam and 20 wt. % SiC particles were fabricated after the infiltration technique by using the newly developed vacuum assisted infiltration procedures. The dry-sliding tribological behavior of A359-SiCp/Fe composites was investigated using the HT-1000 ball-on-disc type high temperature tribometer. The samples were subjected to a variety of temperatures and applied loads to investigate the influence on the wear rate and friction coefficient. In this study, SEM was used to analyses the wear microscopic morphology of A359-SiCp/Fe composites reinforced by iron foam. The wear longitudinal section and the morphology of the wear debris were analyzed by EDS and determined to explore the high-temperature wear mechanism under different temperatures and loads. Hardness analysis from the outer periphery to the core revealed an improvement in hardness. The hardness distribution of the wear longitudinal section is different at different temperatures. The formation of a high-hardness mechanical mixed layer with a different thickness on the wear surface can effectively reduce the wear rate. Microstructural investigations demonstrated that the change in wear debris shape with increasing temperature is mostly related to the change in wear mechanism. Abrasive wear and oxidation wear are the main wear mechanisms. With an increase in temperature and plastic deformation, delamination and adhesion are the predominant wear mechanisms, accompanied by the additional oxidative wear.

High-Pressure Cold Spray Coatings for Aircraft Brakes Application

This paper addresses the potential use of high-pressure cold spray (HP-CS) technology to produce a film of friction material onto a low-carbon steel substrate to allow its use as potential composite material for the stators and rotors of aircraft brake units. Namely, WC-Cr3C2-Ni, WC-Ni, WC-Co-Cr, Cr3C2-NiCr and WC-Co coatings were deposited by using HP-CS, for the purpose of creating high friction and wear resistance composite coatings onto a low-carbon steel substrate. Tribological (friction coefficient and wear rate) and thermal properties as well as coating hardness and adhesion to the low-carbon steel substrate were evaluated to assess the potential use of the coatings as brake surface materials. The tribological and adhesion properties were evaluated by using a pin-on-disk high-temperature tribometer at 450 °C and a scratch test, respectively, whereas coatings hardness was evaluated with a Rockwell C hardness tester. Results obtained show that all coatings exhibit high friction coefficients and low wear rates compared to the low-carbon steel substrate, good adhesion, and elevated microhardness. Furthermore, the WC-Co coating shows better microhardness and thermal properties, while the WC-Co-Cr coating exhibited a better friction coefficient. Unfortunately, it was not possible to quantify the wear resistance due to the elevated roughness of the coatings, but from the analysis carried out on the alumina counterpart of the tribometer, it can be concluded that all the coatings exhibited a very low wear rate. In fact, after the tribological tests, it emerged that the alumina counterpart was more abraded than the investigated coatings.

M-site solid solution of vanadium enables the promising mechanical and high-temperature tribological properties of Cr2AlC coating

Cr2AlC MAX phase coating exhibited excellent oxidation resistance and hot corrosion, but it typically suffered from low hardness and toughness as well as lack of lubrication at high temperature. With a solid solution design on M-site, we demonstrated that the hardness of the Cr2AlC MAX phase coating was enhanced by 34.3% when Cr was partially substituted with V (47 at.%), and the coating toughness was improved simultaneously. Furthermore, according to the high-temperature tribometer test, both the friction coefficient and the wear rate of the coatings at 900 °C against Al2O3 balls were significantly reduced at 47 at.% V. This could be attributed to the formation of a large number of molten V2O5 wrapped (Cr, Al)2O3 hard crystal grains, which not only provided a wide range of liquid-phase lubrication, but also prevented the coating from being apt to wear out. Different from the multi-phase compositing, this study suggested a promising strategy to enhance the combined mechanical and tribological performance of MAX phase coatings by M-site V solid solution for harsh applications at a high temperature of 900 °C.

Comparative investigation on thermally sprayed Al2O3, Al2O3–13%(TiO2) and Al2O3–40%(TiO2) composite coatings from room to 400 °C temperature

In the present study, three coatings of Al2O3, Al2O3–13%(TiO2) and Al2O3–40%(TiO2) composite coatings were deposited by the thermally flame spray process. The comparative wear behaviour of the Al2O3–TiO2 coatings has been studied under high temperature levels up to 400 °C with the help of a high temperature tribometer at a constant load of 40N. Prior to the tribo-test, the coating morphology and elemental analysis has been examined with the help of field emission scanning electron microscope (FESEM), elemental dispersion spectroscopy (EDS) and x-ray powder diffraction (XRD) techniques. The mechanical properties have been also analyzed and reported. The results reveal that specific wear rate decreases with an increase in temperature for all the deposited coating except Al2O3 coating at 400 °C. The overall friction coefficient of the coatings is decreasing with the increasing temperature. The Al2O3–40%TiO2 coating showed maximum sustainability against wear as well as a low coefficient of friction because of its low hardness and high adhesion properties. The examined worn surface validates the presence of brittle fracture and abrasive wear behaviour mechanism along with the oxidation wear, from room temperature to 400 °C.

Simultaneous effect of CaF2 and TiC on tribological properties of ZTA ceramics for high temperature application

Liquid lubrication poses risk to environment; it can vaporize under high temperature or vacuum. Solid lubricant has the potential to replace liquid lubricants due to better stability at severe working environment. This work has been focused to improve tribological properties of zirconia toughened alumina (ZTA) by adding an optimized 4 wt% of CaF2 as a solid lubricant. Since CaF2 is softer material it degrades the mechanical properties of ZTA. To make a balance between the mechanical and the tribological properties, a comparatively harder material TiC is added simultaneously by 10 wt%. All the ceramic composites have been consolidated by hot press sintering at 1500 °C with 30 mins holding time under uni-axial pressing of 50 MPa. Four samples: ZTA, ZTA_CaF2, ZTA_TiC and ZTA_TiC_CaF2 were prepared through the same route. The relative density of the sample (ZTA_CaF2_TiC) achieved was 96.4%. The hardness and fracture toughness has been measured as ∼15GPa and ∼5 MPa m1/2 respectively for the hybrid ceramic composite which is better than ZTA_CaF2 ceramic composite. The tribological characteristics have been evaluated using high temperature tribo-meter with a ball on disc arrangement at 600 °C in vacuum condition. The COF of the ZTA_CaF2 has also been improved by ̴ 39 % compared to the main composite due to the self-lubricating film formation on wear track. A considerable improvement as ∼24.5% in coefficient of friction (COF) and ∼40% in specific wear rate has been found in hybrid ceramic composite as compared to the ZTA ceramic. Thus, it can be used for developing self-lubricating components used in high temperature application.

Effect of Ag content on friction and wear properties of Ag and V co-doped CrN coatings at 25–700 °C

Since the lubrication and wear resistance of important sliding parts are related to the safe operation of the whole system, it is urgent to improve the friction and wear performance of sliding parts in a wide temperature range. On this basis, Ag and V co-doped CrN coatings with varied amounts of Ag were deposited onto silicon wafers and Inconel 718 sheets by unbalanced magnetron sputtering technology. The morphology and elemental composition of the coatings were measured by Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. And the mechanical properties were assessed utilizing scratch tester and nanoindentation. The increase of silver content reduces the mechanical properties of the coating. Excessive Ag not only reduces the hardness and elastic modulus of the Ag and V co-doped CrN coating but also reduces the adhesion between the coating and the substrate. Furthermore, the friction and wear properties of the coatings against Al2O3 balls in a wide temperature (25 °C–700 °C) range were tested by a high-temperature tribometer. CrVN/Ag-0.5A coatings show the lowest wear volume at all temperatures and the lowest friction coefficient at high temperatures. Post-wear testing Raman spectroscopy measurement showed the tribo-chemical products formed on the surface of the coating effectively reduce the coefficient of friction.

Tribological behavior of HVOF based composite coatings for wear resistance applications

In this research work, the sustainable temperature-dependent coating was developed with the use of agriculture waste with the aid of HVOF technology. The various characterization and testing techniques such as Vickers micro-hardness tester, high-temperature tribometer, and FESEM-EDS are practiced for evaluating and examine the microstructures, surface morphology, wear, corrosion, and mechanical properties. The high-temperature tribometer was employed for evaluating the tribological performance of the developed coating and showed the range of value 0.28–0.43 of COF, whereas wear value was received in the range of 42–145 µm at the followings tested conditions of temperature varies from 5 to 200 °C, load (30–60 N) and sliding velocity (0.1–0.4 m/s) respectively. The result obtained from the tribological test shown increment in micro-hardness i.e. 75%, COF decreases 34.88%, and at a temperature of 200 °C, the value of wear is reduced to 71% during the wear test at a SV of 0.4 m/s and applied load of 60 N.

Tribological Analysis of novel Apricot oil based Biolubricant against 15W40 oil tested on High Temperature Tribometer

Nowadays, petroleum products have become an integral part of day-to-day life. Lubricants made from petroleum products were widely used as automobile lubricants. But the use of petroleum-based lubricants has significantly damaged the environment. The concern of environmental damage caused by petroleum-based lubricants has increased the search for environmentally friendly lubricants. The vegetable oil-based lubricants proved to be environmentally friendly. In the present work, a bio lubricant is produced from the apricot oil, scientifically known as Prunus Armeniaca, using the trans-esterification method. The tribological behavior is analyzed for pure bio-lubricant, 15W40 oil, and also for the blend of apricot oil and 15w40 at different volume percentages. A high-temperature Pin on disc tribometer is used to perform friction and wear tests at 40oC and 100oC. It was found that the blend of apricot oil-based biolubricants and 15W40 lubricant showed better tribological behavior as compared to the pure bio-lubricant and 15W40 oil alone.

Fabrication and high temperature tribological properties of WC reinforced W-Cu composites

In this study, WC doped W-Cu composites with high hardness and excellent tribological properties were prepared using hot pressing sintering with Cu coated W composite powders. Friction and wear behaviors of W-Cu-WC composites and W-Cu composites against Si3N4 balls at room and high temperatures (e.g., 25 ℃, 700 ℃ and 900 ℃) were investigated using a ball-on-disk high temperature tribometer in vacuum. Results showed that the Vickers hardness of WC doped W-Cu composites (245 HV) was relatively higher than that of the W-Cu composites. The specific wear rate of WC doped W-Cu composites was lower than that of the W-Cu composites in the temperature range of 25–900, and that at 700 °C (56.3 × 10−5 mm3/Nm) was an order of magnitude lower than that of the W-Cu composites. The wear resistance of W-Cu composites doped with WC particles was dramatically improved in vacuum. The dominant wear mechanisms of W-Cu composites were abrasive wear, adhesive wear and delamination at various temperatures, whereas the dominant wear mechanisms of W-Cu-WC composites were abrasive wear and delamination at various temperatures. Data availability statementThe data will be made available upon request.

Residual, Corrosion & Tribological Behavior of HVOF Sprayed Sustainable Temperature-Dependent Carbon-Based Hybrid Composite Coating

At present, cost-effective coatings that cause less pollution are in great demand; to decrease frictional losses, carbon-based hybrid composite coatings have been developed using a high-velocity oxy-fuel (HVOF) spray process. The microstructural, tribological, corrosion, and mechanical properties of these coatings have been evaluated using high-resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy-Energy dispersive X-ray Spectroscopy (FESEM-EDS), Raman spectrum, Vickers micro-hardness tester, µ-360 cos(α) residual stress analyser, corrosion tester, and high temperature tribometer. The residual stress, corrosion and tribological behaviour at high temperatures were investigated using a pin-on-disc high-temperature tribometer. The tribological performance was evaluated using a high-temperature tribometer, and the experimental result shows that a coefficient of friction (COF) varies from 0.12 to 0.52, while wear results were in the range of 45 µm to 120 µm, as the test condition of temperature ranging from 50 °C to 350 °C, load from 60 N to 90 N and sliding velocity from 0.1 m/s to 0.4 m/s respectively. The experimental results of corrosion testing show that the mass loss decreases from 0.10 g to 0.04 g, when samples were dipped for 1 h; when the samples were dipped for 8 h, the mass loss of hybrid composite coating varied from 0.12 g to 0.045 g. The tribological test showed a 78.9 % increase in micro-hardness, a 78 % decrease in residual stress, and 60 % and 62.5 % decreases in mass loss due to corrosion at 1 h and 8 h, respectively, a 76.9 % decrease in COF and 62.5 % reduction in the wear at test condition of 350 ºC temperature, a sliding velocity of 0.4 m/s and 90 N load.

Microstructure and high-temperature wear behaviour of Inconel 625 multi-layer cladding prepared on H13 mould steel by a hybrid additive manufacturing method

To improve the high-temperature performance of a hot-working mould, high-temperature wear-resistant multi-layer laser cladding was prepared on the forming surface of the mould by a hybrid additive manufacturing (HAM) method. First, an Inconel 625 multi-layer cladding was fabricated on the H13 mould steel by laser cladding. Then, the multi-layer laser cladding was milled by CNC. Finally, the milled multi-layer cladding was subjected to ultrasonic surface rolling (USR) treatment. The microstructure and high-temperature wear behaviour of the multi-layer cladding prepared by HAM were studied using SEM, EDS, and a high-temperature tribometer. The results show that the multi-layer laser cladding after USR has a smooth nanolayer. The surface roughness is below 0.15 μm. The multi-layer cladding has better high temperature wear resistance than the substrate. The microstructure of the multi-layer cladding from the surface to the substrate is composed of coaxial, columnar, and dendritic grains. After USR treatment, the dendritic grains are grown in the processing direction and significantly refined.

Effect of load on the behaviour of tribofilms formed at the interface of austenitic steel and ductile iron – a Raman spectroscopic study

ABSTRACT This paper presents Raman spectroscopic characterization of the tribofilms formed during dry sliding at the interface of an exhaust valve material, austenitic steel 21–4 N and valve-seat material, ductile cast iron GGG-40, at loads of 20–50 N at a temperature of 500°C. The behaviour of the tribofilms formed at the contact interface with increasing loads is highlighted. Pin-on-disc experiments were conducted on a high-temperature tribometer and low coefficient of friction (COF), in the range of 0.12–0.15, was observed at loads up to 40 N which increased by 35% to 0.19 at a load of 50 N. Scanning electron micrographs indicate the presence of well-developed tribofilms at lower loads while the formation, subsequent deterioration and finally the reformation process of tribofilms is observed at the higher loads. Energy dispersive spectroscopy analysis primarily indicates the presence of oxides of Fe in the tribofilm region. Ex-situ Raman spectroscopy confirms the presence of haematite (α-Fe2O3) on the wear tracks, especially at loads of 20–40 N. However, the spectra indicate a strong presence of magnetite at a load of 50 N. It is observed that haematite is a major constituent of the wear protective tribofilms.

Cold Spraying: A New Alternative Preparation Method for Nickel-Based High-Temperature Solid-Lubrication Coating

Cold spraying was first used for the purpose of preparing nickel-based high-temperature lubrication coatings. High-quality In625-Cr2O3-Ag composite coatings were deposited by a high-pressure cold-spray system, and their tribological properties were evaluated at 20 and 1000 °C by a high-temperature tribometer. The microstructure, composition, and wear mechanisms of the coatings were analyzed by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The measurements showed that the cold-sprayed In625-Cr2O3-Ag composite coatings have a very dense structure, good bonding strength to substrate, low friction coefficient, and excellent wear resistance. The friction coefficients of the In625-Cr2O3-Ag coatings were around 0.3 and the wear rates of the coating were maintained at about 10−5 mm3/N m at 20 and 1000 °C. The experimental observation of the wear tracks revealed that the silver provided lubrication at 20 °C. As the temperature increased up to 1000 °C, a lubrication layer with low shear strength made up of Ag2MoO4 and Cr2O3 was formed on the wear track.

Nickel alloy C-263 protection by WC[sbnd]Cr3C2[sbnd]Ni coatings against high-temperature wear in nuclear applications

Over the years, substantial improvement in the thermal efficiency resulted in higher operating temperatures for Generation IV nuclear reactors. Therefore, reliable material demanded by designers that could sustain at elevated temperatures environment in nuclear applications. The high-temperature friction and wear behaviour of Ni-based alloy C-263 has been comparatively investigated with WCCr3C2Ni coatings. The commercially available WCCr3C2Ni powder deposited by atmospheric plasma spray (APS) and high-velocity oxy-fuel (HVOF) processes. The high-temperature tribometer used for unidirectional sliding tests at 400 °C, 600 °C and 750 °C. The alloy shows higher specific wear rates compared to both coatings at every temperature interval. Development of tribo-film is responsible for the specific wear rates of both the coatings declined after 600 °C. Consequently, the superior wear resistance than Ni-alloy up to 750 °C recommends WCCr3C2Ni coatings for high-temperature gas-cooled nuclear reactors.

Microstructure of HVOF-sprayed Ag–BaF2⋅CaF2–Cr3C2–NiCr coating and its tribological behavior in a wide temperature range (25 °C to 800 °C)

Ag–BaF2⋅CaF2–Cr3C2–NiCr composite powders were prepared by physically blending commercial BaF2⋅CaF2–Cr3C2–NiCr and Ag powders. Ag–BaF2⋅CaF2–Cr3C2–NiCr composite coatings were deposited on Inconel 718 alloy substrate by high velocity oxy-fuel (HVOF) spraying. The friction and wear behavior of the coatings under dry sliding against Si3N4 balls from 25 °C to 800 °C was evaluated with a ball-on-disk high temperature tribometer. The microstructure and composition of the samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrometer. Results showed that the composite coatings were mainly composed of hard phase of Cr3C2, binder phase of NiCr, high-temperature lubrication phase of fluorides and low-temperature lubrication phase of Ag. The fluorides existed in the forms of both crystal particles and amorphous state, while the silver featured as typical thermally sprayed splats. Due to the high flame temperature, some fluorides have been oxidized to chromates and around 30 wt% of Ag was lost during spraying. In addition, it was found that Ag content had an important influence on the composite coating, and an appropriate dosage of metallic silver could effectively improve the tribological performance of the coating. The generation of AgCrO2 at moderate (500 °C and 650 °C) temperature and BaCrO4 at high temperature (800 °C) could contribute to the decline in friction coefficients and wear rates of Ag–BaF2⋅CaF2–Cr3C2–NiCr coatings.

Effect of Vanadium Addition on the High-Temperature Friction Behavior in Nanostructured Al-Cr-V-N Films Prepared by UBMS.

In recent year, vanadium-doped tribological films have become available as possible candidates for self-lubrication at high temperatures. In this work, quaternary Al-Cr-V-N films were deposited onto silicon wafer and WC-Co substrates by an unbalanced magnetron sputtering using high purity (99.99%) CrAl₂ and V targets with argon-nitrogen reactive gases. EPMA results revealed that vanadium atoms can incorporated from 0 to 13 at.% into the films. The maximum hardness value was ~32 GPa at vanadium content of 7.1 at.% in the Al-Cr-V-N films. The high-temperature tribometer was used to analysis the friction characteristics of the films with elevated temperature. As a result of the high temperature friction test after heating up to 700 °C, the average friction coefficient decreased from 0.62 to 0.35 with increasing of vanadium contents in the Al-Cr-V-N films. It is concluded that the reduction of the friction coefficient is attributed to the formation of V₂O5, which is a Magnéli phase that acts as a lubrication at high temperature.