High Temperature Friction Behavior Research Articles

Study on High-Temperature, Ultra-Low Wear Behaviors of Ti6Al4V Alloy with Thermal Oxidation Treatment

Thermal oxidation (TO) is a simple and economical way to enhance the wear resistance of the Ti6Al4V alloy. The TO temperature has a very important effect on the tribological properties of the TiO2 layer formed. However, the impact of the oxidation temperature on the high-temperature tribological behavior of a TO-treated Ti6Al4V alloy is not clear. Therefore, the Ti6Al4V alloy was oxidized at 400 °C, 600 °C, and 700 °C for 36 h, and the sliding friction experiments were conducted at room temperature (RT) and 400 °C with a Si3N4 ball as the counter body to comparatively study the effect of the oxidation temperature on the high-temperature friction behavior of the TO-treated Ti6Al4V alloy. The results show that the TO treatment can effectively improve the wear resistance of the samples at both room and high temperatures. Among them, the oxidation-treated samples at 700 °C show the best wear resistance, with a reduction of 92.6% at high temperatures; the amount of wear loss at room temperature was so small that it was almost incalculable. At room temperature, the friction surface formed uneven agglomerate formations, resulting in an elevated coefficient of friction (CoF) compared to the untreated samples. At a high temperature, however, the CoF is reduced compared to the untreated samples due to the formation of a homogeneous transfer film in the wear area that is caused by the interaction of Si3N4 and oxygen.

Friction and wear behavior of molybdenum-disulfide doped hydrogen-free diamond-like carbon films sliding against Al2O3 balls at elevated temperature

Diamond-like carbon (DLC) films quickly experience lubrication failure due to oxidation and mechanical degradation when used above 300 °C, which limits their application. Molybdenum disulfide (MoS2) doping is considered as a feasible method to improve high-temperature properties of DLC films. However, the effect of MoS2 doping on the high-temperature friction behavior of MoS2-DLC composite films and its mechanism remain unclear. Here, MoS2-DLC composite films with different contents of MoS2 were synthesized by a superimposed deposition system consisting of high-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS). The MoS2 content in the films was controlled by varying the number of MoS2 pellets in the graphite-MoS2 (C–MoS2) mosaic target. The effect of MoS2 doping content on the structure and mechanical properties of MoS2-DLC films was analyzed. In addition, the friction and wear behavior and mechanism of MoS2-DLC composite films sliding against Al2O3 balls at 25–450 °C were studied. The results indicated that MoS2 was successfully incorporated into DLC matrix, and the content of Mo in the films ranged from 0 to 6.15 at. %. The as-deposited MoS2-DLC composite films exhibited a dense and featureless structure. The doping of MoS2 improved the adhesion strength and released the internal stress of MoS2-DLC composite films, but reduced the hardness and elastic modulus of the films. In particular, MoS2-DLC composite films with 3.78–6.15 at. % Mo maintained excellent anti-friction and anti-wear performances in the temperature range of 25–450 °C. Abrasive wear and fatigue wear occurred in the friction test of the films at different temperatures. However, the friction mechanism of the films varied with the temperature of friction test. At 25 °C, MoS2-DLC composite films showed excellent lubrication and anti-wear abilities due to the carbon suspension bond was passivated by H2O molecules. At 250 °C, MoS2 phase precipitated on the surface of the films, resulting in low friction. At 350 °C, MoS2-xOx solid solution was generated on the surface of the wear track to maintain lower friction and wear. Interestingly, MoS2-DLC composite films with high Mo content still achieved relatively low coefficient of friction and wear rate up to 450 °C due to the continuous availability of MoS2-xOx generated on the surface of wear track.

The Oxide Layer of 10Mn5 Medium Manganese Steel for Wear Protection in High-Temperature Friction during Hot Stamping

A custom-designed high-temperature sliding-on-sheet-strip (SOSS) tribo-tester was used to simulate the high-temperature friction process of 10Mn5 medium manganese steel bare plate under actual hot stamping conditions. To reveal its high-temperature friction mechanism in the hot forming process, the high-temperature friction behavior of 10Mn5 steel and 22MnB5 steel was compared. The scanning electron microscope (SEM), energy spectrum analyzer (EDS) and X-ray diffractometer (XRD) were used to investigate the structure of the oxide layer, composition of physical phase, wear surface morphology and elemental composition. The results show that the average coefficient of friction of 10Mn5 steel is 12.7% lower than that of 22MnB5 steel. The cross-section of both steel consists of an oxide layer, an alloying element-rich layer and the matrix. The oxide layer of 10Mn5 steel is mainly composed of Fe3O4, approximately 63.7%, while that of 22MnB5 is mainly composed of Fe2O3, approximately 66.9%. The complete and less flaking scale of 10Mn5 steel provides good wear protection, and the mechanism is abrasive with slight adhesive wear. Meanwhile, oxide particles and fragments are embedded in the 22MnB5 surface thus increasing the wear, and the mechanism evolves into severe abrasive and adhesive wear. The difference in the mechanism between the two steels is mainly caused by different austenitizing temperatures, which for 10Mn5 is lower than 22MnB5, about 100 °C. This makes the thermal stress of 10Mn5 from the temperature difference between the furnace and the environment not enough to break the scale and decrease abrasion.

The effects of die temperature and cooling condition on friction behavior of bare 22MnB5 boron steel in hot stamping

ABSTRACT Hot stamping is an effective method to improve both the elongation and plasticity of ultra-high strength steels, thus a higher specific strength could be achieved, making it possible for weight reduction in motor vehicles. However, due to the die temperature rise and the cooling liquid within hot stamping applications, the friction in its forming stage is always a non-isothermal mode. Therefore, a high-temperature sliding-on-sheet-strip (SOSS) tribo-tester to simulate sliding friction in hot stamping of 22MnB5 hot stamping steel sheet was designed and custom-made. Then, it was employed to exploit High-temperature friction behavior and mechanism of bare 22MnB5 hot-stamping boron steel sheet under different die temperature and extra cooling conditions. Results show that the friction coefficient obtained under the pure die cooling conditions is lower than that obtained under extra cooling conditions, which is attributed to the formation of thicker oxide layers on the surface of specimen during the cooling process. In addition, the friction coefficient is obviously decreased when the die temperature increased to 200 °C, which is ascribed to the co-action of the destruction of the oxide layers and the formation of bainite.

High-temperature friction behavior of amorphous carbon coating in glass molding process

In the glass molding process, the sticking reaction and fatigue wear between the glass and mold hinder the service life and functional application of the mold at the elevated temperature. To improve the chemical inertness and anti-friction properties of the mold, an amorphous carbon coating was synthesized on the tungsten carbide-cobalt (WC–8Co) substrate by magnetron sputtering. The friction behavior between the glass and carbon coating has a significant influence on the functional protection and service life of the mold. Therefore, the glass ring compression tests were conducted to measure the friction coefficient and friction force of the contact interface between the glass and amorphous carbon coating at the high temperature. Meanwhile, the detailed characterization of the amorphous carbon coating was performed to study the microstructure evolution and surface topography of the amorphous carbon coating during glass molding process by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Ramon spectroscopy, and atomic force microscope (AFM). The results showed that the amorphous carbon coating exhibited excellent thermal stability, but weak shear friction strength. The friction coefficient between the glass and coating depended on the temperature. Besides, the service life of the coating was governed by the friction force of the contact interface, processing conditions, and composition diffusion. This work provides a better understanding of the application of carbon coatings in the glass molding.

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.

The process of surface carburization and high temperature wear behavior of infiltrated W-Cu composites

Tungsten-copper (W-Cu) composites are used as high temperature frictional materials under special service conditions for electromagnetic gun rail and precision guide for rolled pieces due to their good ablation resistance and electrical conductivity. However, they have poor wear resistance at elevated temperatures. In this paper, surface carburization method was applied on the W-20 wt%Cu composite to investigate the mechanisms of carburization and its effects on the high temperature friction behavior of composite. Carburization process has been done at a temperature of 1100 °C for 30 h. The obtained results showed that carburizing at 1100 °C with a dwelling time of 30 h resulted into formation of a carburized layer and a dense intermediate sub-layer on the substrate. Also, the surface carburized layer with a thickness of about 70 μm composed of mixed phases of graphite, WC and W2C. The hardness of carburized layer (~HV454) was significantly higher than that of substrate (HV223). Also, bending strength of the carburized W-Cu composites has been significantly improved, although their electrical conductivity and tensile strength was decreased slightly. The carburization mechanism of the W-Cu composites was found to be dominant by carbon atom diffusion through reaction with W atoms and formation of surface liquid copper, which promoted migration and diffusion of tungsten and carbon at high temperatures. Average coefficients of friction and wear rate of carburized W-Cu composites are all lower than these of un-carburized W-Cu composites owing to the presence of surface carburized layer. Also, formation of CuWO4 at high temperatures reduced the friction and wear resistance of the W-Cu composites.

Fabrication and High Temperature Friction Behavior and Oxidation Resistance of Ni-Co-ZrO2 Composite Coating

Ni-Co alloy and ZrO2 micron particles were codeposited on 45 carbon steel by electrodeposition. The composition and microstructure of the composite coating were characterized. The high temperature tribological properties were carried out by a pin-on-disk tribo-tester. Additionally, the oxidation resistance was evaluated via high temperature circulating oxidation test. The results indicated that the deposited composite coating showed dispersed ZrO2 particles and continuous Ni-Co matrix, and there were no obvious pores, cracks and other defects at the interface between the composite coating and the substrate. The embedded ZrO2 particles changed the friction mechanism from adhesive wear to abrasive wear, the wear loss rate and friction coefficient of Ni-Co-ZrO2 composite coating were lower in comparison with that of Ni-Co alloy coating and carbon steel substrate. In addition, the embedded ZrO2 particles exerted a reactive-phase effect on the growth of nickel oxide and cobalt oxide, and effectively reduced the oxidation rate of the substrate at high temperature. Therefore, the Ni-Co-ZrO2 composite coating presents better oxidation resistance, when compared with Ni-Co coating.

High temperature friction behavior of CrVxN coatings

The object of this research is to deposit CrVxN coatings with different content of Vanadium (V) by ion-sputter deposition to gain fundamental knowledge on the friction behavior of these coatings under high temperature and to analyze stick–slip phenomenon. The results of stick–slip tests under low sliding velocities are compared with real contact conditions. Here, an entirely new method is established to approach this problem at different scales by combining high-temperature friction study of coatings (Fraunhofer Institute for mechanics of materials, IWM), and micro-tribology for stick–slip analysis (Holon Institute of Technology, HIT). The tribological experiments at Fraunhofer IWM were performed using an oscillating friction-wear test rig (SRV4, Optimol Instruments) in the temperature range of 25 to 700°C. To study stick–slip phenomena, a new ball on flat device with a heated chamber for experiments at up to 500°C was developed at the HIT. It was shown that an addition of V up to 27–35at.% in CrVxN coatings increases the hardness, fracture toughness and decreases the grain size. These parameters correlate with improved tribological properties of coatings with high content of V. At room temperature CrVxN coatings feature strong sticking effects in the friction experiments. High values of the stick–slip parameters are explained by mechanical interlocking and adhesion on contact spots due to softening of surface layers of balls, high roughness and transfer of thick iron oxide films on the surface of the coatings. Low values of the wear and stick–slip parameters under friction of Cr0.65V0.35N at high temperatures (T=500–700°C) is associated with the formation of V2O5 oxide phase providing easy shearing of tribofilms in the interface of rubbed surfaces.

Effect of La2O3 on microstructure, mechanical and tribological properties of Ni-W coatings

In this paper, a Ni-W-La2O3 composite coating was prepared by the electrodeposition method. Microhardness tester and environmental scanning electron microscope equipped energy dispersive spectroscopy were employed to investigate the microhardness and the surface morphology of the composite coatings respectively, and the high temperature friction behavior and corrosion resistance of the coatings against molten glass were investigated by using a high temperature tribometer. The results show that La2O3 can refine the microstructure effectively, and make the element distribution uniform, which leads to the increase of average microhardness. La2O3 particulates can reduce the friction coefficient between the composite coating and glass during the sliding process at about 973 K largely, and the corrosion resistance of the La2O3 added Ni-W coatings is effectively improved compared with that of the non-added one, furthermore the mechanism of friction-reducing and anti-corrosion is also discussed.

Effect of nano-sized CeF 3 on microstructure, mechanical, high temperature friction and corrosion behavior of Ni–W composite coatings

Ni–W–CeF 3 composite coatings were prepared by electrodeposition in a Ni–W plating bath containing CeF 3 nano-particles. The shape and size of the CeF 3 nano-particles and the surface topography of the composite coatings were observed using an environmental scanning electron microscope, and the component and structure analysis was characterized by means of XRD. A microhardness tester was employed to investigate the microhardness of the coatings. The high temperature friction behavior and corrosion resistance of the coatings against molten glass were investigated by using a high temperature tribometer. It was found that the CeF 3 nano-particles appeared in the coatings as microspheres of a diameter less than 50 nm. The addition of CeF 3 nano-particles led to changes in morphologies of the composite coatings by refining the size of crystalline bulks. Therefore, the Ni–W–nanoCeF 3 composite coatings had more compact and fine granular morphologies. The co-deposited CeF 3 nano-particles were uniformly distributed in the Ni–W matrix and had contribution to greatly increasing the microhardness, high temperature tribological and anti-corrosion properties of the Ni–W alloy, furthermore the mechanism of anti-friction and anti-corrosion is discussed.

Tribological and anti-corrosion properties of Ni–W–CeO 2 coatings against molten glass

Composite plating was used to prepare Ni–W infused rare earth oxide CeO 2 composite coatings. The high temperature friction behavior and corrosion resistance of the coatings against molten glass were investigated by using a high temperature tribometer. A microhardness tester and an environmental scanning electron microscope equipped energy dispersive spectroscopy were employed to investigate the microhardness and the surface morphology of the composite coatings respectively. The results show that the brittle fracture, high temperature tribological properties and the corrosion resistance of Ni–W infused CeO 2 coatings are superior to those of a standard Ni–W coating. CeO 2 particles decrease the friction coefficient from nearly 0.5 to about 0.25 during the composite coatings sliding against the molten glass at about 973 K, and proper quantities of CeO 2 decrease the variation of the friction coefficient value. Furthermore, CeO 2 can improve the corrosion resistance of the Ni–W coatings at high temperature effectively.