High Temperature Tribological Behaviors Research Articles

High temperature tribological behaviors and wear mechanisms of NiAl–NbC–Ag composites formed by in-situ decomposition of AgNbO3

Abstract NiAl–NbC–Ag composites were successfully prepared by vacuum-hot-pressing sintering with directly addition of AgNbO3 powders, where AgNbO3 were synthesized using a solid state reaction method. The tribological behaviors of composites were evaluated from 25 °C to 800 °C. The consequences reveal AgNbO3 are completely decomposed during sintering process and in-situ formed NiAl–NbC–Ag composites, which hold excellent high temperature tribologicial properties. At mid-low temperature, NAB20 (NiAl-20 wt%AgNbO3) has a relative lower friction coefficient compared to NiAl, which was attributed to the existence of Ag. While the lowered friction coefficients at 600 °C and 800 °C were attributed to the lubricating glaze layers formed by tribo-chemical reaction on the worn surfaces, which were consisted of typical layered structure Ag2Nb4O11, perovskite AgNbO3 with a highly flexible crystal structure and AgNb3O8.

The effect of pre-oxidation on microstructure, mechanical properties and high-temperature tribological behaviors of HVOF-sprayed NiCoCrAlYTa coating

Abstract The HVOF-sprayed NiCoCrAlYTa coating would generate a dense oxidative layer under high temperature so that the microstructure, chemical component, mechanical properties and high-temperature tribological behaviors of the coatings surface were changed significantly. The as-sprayed NiCoCrAlYTa coating is mainly composed of the phases of γ-Ni and β-NiAl as well as γ′-Ni3Al. The Al-rich phase of β-NiAl in the post-oxidized coating has disappeared, replaced by the emergence of α-Al2O3. The formation of the oxidative layer with α-Al2O3 columnar crystal could greatly improve the mechanical properties of the NiCoCrAlYTa coating. Along with the elevated temperature, the friction coefficient and wear rate of as-sprayed coating gradually decreased, and the primary mechanism changed from abrasive wear to adhesive wear. Although the friction coefficient of the post-oxidized coating is slightly higher than that of as-sprayed coating, the wear rate decreases, obviously. This is because the oxidative layer of post-oxidized coating exerts a great influence on the wear resistance, especially under the high temperature.

Effects of temperature and microstructure on the triblogical properties of CoCrFeNiNbx eutectic high entropy alloys

This paper is aimed to evaluate the high temperature tribological behaviors of CoCrFeNiNbx eutectic high entropy alloys which would be highly-promising candidates for high-temperature applications. The effects of testing temperature and material structure on the friction and wear properties are investigated. The CoCrFeNiNbx alloys display a low harness decrement rate about 35% from room temperature to 1000 °C, indicating good softening resistance. The main wear mechanisms are abrasion wear at room temperature, change to adhesion wear at 400 °C, and translate into oxidation wear and mechanical wear over 600 °C. The wear rates increase from room temperature to 400 °C and decrease afterwards. The effects of material structure are dominated by the hardness of alloy, the content of chemically active Nb element and the structure of oxidized tribo-layer. The compact oxidized tribo-layers with excellent anti-wear properties are formed on the worn surface of CoCrFeNiNb0.65 and CoCrFeNiNb0.8 alloys at 800 °C, leading to extremely low wear rate.

In-situ formation of Ni-Al intermetallics-coated graphite/Al composite in a cold-sprayed coating and its high temperature tribological behaviors

In this study, cold spraying (CS) was used to deposit a mixture of nickel-coated graphite and 40vol.% Al powder (Ni-Gr/Al) on a steel substrate aiming to effectively preserve a certain volume fraction of graphite in the deposited Ni-Gr/Al composite coating. The microstructure of the as-sprayed coating and the effect of post-spray heat-treatment (PSHT) temperatures on the in-situ formation of Ni-Al intermetallic phases in coating were studied. The tribological behaviors of the as-sprayed coating and the PSHTed coating under 450°C were tested at 25°C, while the as-sprayed coating was tested at 450°C for comparison. As a result, the Ni-Gr particles showed a homogenous distribution in the coating. The multilayer Ni-Al intermetallics-coated graphite/Al composite coating was achieved in situ after the PSHT of 450°C, where the graphite did decompose at 550°C leaving big pores in the coating. The coefficients of friction (COF) of the CSed coating and the PSHTed coating were measured at 450°C as well as 25°C, which showed a similar tendency, much higher than that of the CSed coating tested at 25°C. The lubrication phase (graphite) improved the formation of a graphite film during sliding friction and decreased the COF, while the hard Ni-Al intermetallic phases contributed to the increase of COF.

High-temperature tribological behaviors of a Cr-Si co-alloyed layer on TA15 alloy

A Cr-Si co-alloyed layer was successfully deposited on TA15 alloy by the double glow plasma surface technology to improve its poor wear resistance at elevated temperature. The microstructure, composition, and phase structure of the layer were investigated by SEM, EDS, and XRD. The tribological behaviors of the Cr-Si co-alloyed layer at 20°C and 500°C were analyzed in details. The results indicated that the friction coefficient and wear rate of the Cr-Si co-alloyed layer at 20°C and 500°C were much lower than those of the substrate, which was due to higher hardness and superior elastic modulus. This layer may become an approach to effectively improving the wear resistance of TA15 alloy at elevated temperature.

Structure and high temperature tribological behavior of TiAlN/nitride duplex treated coatings on Ti6Al4V

Abstract The duplex treatment of nitriding and TiAlN coatings was employed to improve the wear resistance of the Ti6Al4V alloy at higher temperature. Mechanical properties, microstructure and high temperature tribological behaviors were investigated by ball-on-disc wear test at elevated temperatures from 25 °C to 600 °C in atmosphere. The duplex treated sample exhibits a superior adhesion compared with only TiAlN coated sample due to a good load-carrying capacity. In addition, the duplex treated sample possesses excellent abrasion resistance at all temperatures. Particularly, the duplex treated sample has the lowest wear rate at 500 °C due to the formation of Al 2 O 3 and TiO 2 .

Study on the Friction Factor and High-Temperature Friction Resistance of Semi-Metal Frictional Materials

The orthogonal experimental study is carried out to study the Incorporation of different proportion of functional components and the effect on tribological performance among semi-metallic friction materials. A test is conducted for each sample on XXD-MSM constant speed tester in accordance with Brake Linings for Automobiles (GB5763-2008). The friction factor and high-temperature abrasion resistance properties are evaluated along with the obtaining of optimal formula, and the mechanism of affecting the tribological properties is analyzed on the worn surfaces by using a scanning electron microscope (SEM). The study results indicate that the high-temperature friction stability could be deeply affected by the adequate content of steel fiber, Kevlar pulp, potassium hexatitanate whisker and cashew nut shell. The mechanism of High-temperature tribological behaviors are the thermal decompositions. The thermal decomposition of organic matter might greatly weakened the bonding effect. The thermal decomposition of tribo-film fall off as lamellar chip under the effect of friction stress. The addition level of nanoparticles is 3%, the sample’s tensile strength, tensile strength, hardness index and noise level are better. If the modified resin is further applied, this formula can be close to the index of excellent Chinese industrial product JF04-20.

High temperature tribological behaviors of (WAl)C–Co ceramic composites with the additions of fluoride solid lubricants

The tribological behaviors of the (W0.67Al0.33)C0.67–Co/fluoride (CaF2, BaF2, CaF2/BaF2) composites against SiC ball from room temperature to 600 °C were investigated. A marked increase in the friction coefficient resulting from fluoride oxidation was observed as the temperature increased. The composites containing BaF2 or (Ca, Ba)F2 displayed better integrated wear resistance over a wide temperature range compared with (W0.67Al0.33)C0.67–Co/CaF2. The high temperature tribological characteristics of the three composites were distinct, which originated from the composition difference on the worn surfaces. First, the SiO2/SiC film formed on the worn surfaces of the composites with BaF2 or (Ca, Ba)F2 was favorable for their wear resistance. Second, the oxidation of WC matrix was an important factor influencing the wear resistance of the composites. When mixture oxides of WO2 and WO3 appeared on the surface, wear is severe. In addition, single WO3 formed on the worn surfaces, appeared more adhesive to the underlying substrate and decreased the wear rate.

Influence of air-plasma treatment and hexagonal boron nitride as filler on the high temperature tribological behaviors of hybrid PTFE/Nomex fabric/phenolic composite

In this work, we investigated the effect of air-plasma treatment on the bonding strength of hybrid PTFE/Nomex fabric and mechanical strength of PTFE and Nomex fibers. Besides, we employed hexagonal boron nitride (h-BN) as high-temperature lubricant and incorporated it into the hybrid fabric/phenolic composite. The high-temperature tribological performances of the fabric composite were evaluated on a pin-on-disk tribometer. The results indicated that the air-plasma treated hybrid PTFE/Nomex fabric composites filled with 6wt%h-BN exhibited outstanding tribological properties. The results of the morphology study of the fabric composites support the results of the wear test and the corresponding wear mechanisms of the composites were discussed based on the characterizations.

High temperature tribological behaviors of plasma electrolytic borocarburized Q235 low-carbon steel

Plasma electrolytic boronizing is a novel technique to fabricate rapidly a hardening layer on steel. In this study, a boride layer on Q235 low-carbon steel was prepared by plasma electrolytic borocarburizing process (PEB/C) in the 30% borax electrolyte with carbon-containing organic additive at 330V. The microstructure and phase constituent of the PEB/C steel were analyzed by SEM and XRD. Microhardness profile of the PEB/C steel was determined, and its tribological properties under dry sliding against ZrO2 ceramic ball were evaluated using a ball-on-disk friction tester at ambient temperature and high-temperature (up to 500°C) environments. Friction coefficient and wear rate before and after PEB/C treatment were measured, and the wear mechanism was also discussed. The results show that the boride layer mainly consists of the Fe2B phase, the hardness of which is close to 1800HV. The PEB/C treatment could significantly decrease the friction coefficient and improve wear resistance of the low-carbon steel. Meanwhile, the friction coefficient and wear rate of the untreated and PEB/C treated steel samples also increase with increasing the environment temperature, but the wear rate of PEB/C treated steel is always much lower than that of the untreated steel at different environment temperatures. Plasma electrolytic borocarburized low-carbon steel can maintain higher wear resistance at high temperature environment, which ascribes to the formation of Fe2B phase with good thermal stability in the hardening layer. The wear mechanism of untreated low-carbon steel is mainly the fatigue wear at ambient temperature and the fatigue wear and adhesive wear at 200°C. The PEB/C treated steel displays the adhesive wear at 200°C. However both the untreated and PEB/C treated samples are transferred to the oxidation wear and adhesive wear at 500°C.

Elevated temperature dry sliding wear behavior of nickel-based composite coating on austenitic stainless steel deposited by a novel central hollow laser cladding

In order to improve the high-temperature wear resistance of austenitic stainless steel, a wear resistant composite coating reinforced with hard (Cr,Fe) 7C 3 carbide and toughened by ductile γ-(Ni,Fe)/(Cr,Fe) 7C 3 eutectic matrix was fabricated by a novel central hollow laser cladding technique. The constituent phases and microstructure as well as high-temperature tribological behaviors of the Ni-based coating were investigated, respectively, and the corresponding wear mechanisms were discussed. It has been found that the composite coating exhibits superior wear resistance than substrate either at ambient or high temperatures. The coating shows better sliding wear resistance at 600 °C than 300 °C owing to high-temperature stability of the reinforced carbide and polishing effect as well as formation of continuous lubricious films, which implied it has large potential industrial applications at relatively higher temperatures.

High-temperature tribological behaviors of Ti 2AlNb-based alloys by plasma surface duplex treatment

Plasma tungstening followed by carburization (W-C duplex treatment) was performed on the Ti 2AlNb-based ( O phase) alloy by using the double glow plasma process to enhance its wear resistance. The microstructure and high-temperature tribological behaviors of the un-treated and W-C duplex-treated samples were investigated. The results show that the duplex-treated layer is mainly composed of W 2C or W 6C 2.54 phases and the contents of W and C elements in the alloyed layer change gradually along the depth by surface plasma duplex treatment. The diffusion depth of W is about 12 μm, while the carbon atoms most exist in the depth more than 12 μm. High temperature tribometer tests indicate that the friction coefficient of the W-C duplex-treated layer is approximately 1/6 that of substrate. The wear rate of the duplex-treated layer is about 28% that of the untreated one. So, plasma surface W-C duplex treatment can obviously improve the high-temperature tribological resistance of Ti 2AlNb-based alloy. The tribological mechanism of the duplex-treated layer is discussed by dividing the friction process of the duplex-treated layer into three fluctuate stages. The first stage is the formation of oxide film between W-C duplex-treated layer and counterface. The second stage is the detachment of oxide film, acting as “the third body”. The last stage is the period that the friction and wear occur between the compact particle layer and counterface.

High temperature tribological behaviors of nano-diamond as oil additive

The tribological behaviors of the nano-diamond particles including the nano-diamond and the nano-diamond modified were studied at high temperature using SRV multifunctional test system. The worn steel surfaces were analyzed by means of X-ray photoelectron spectroscopy (XPS). The results show that nano-diamond particles can obviously improve the antiwear and friction reducing properties of the base oil at high temperature and the high load. The friction coefficient of the nano-diamond is very low at 200 °C when the test load is not more than 20 N. This tribological behaviors should attributed to the similarly to “ball bearing” lubrication action of the nano-diamond particles, so the movement between tribological pairs become sliding/rolling. The nano-diamond modified by dimer ester possesses excellent antiwear and friction reducing performance at 500 °C and load 500 N. The tribochemical reaction film between the nano-diamond particles and the renascent wear surface plays dominating lubrication role and the presence of the dimer ester on the rubbing surface can be propitious to form lubrication film containing nano-diamond on the worn surface at high temperature and high load.