Wear Mass Research Articles

Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

A series of Al2CrFeNiMo x (x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

Effect of Temperature on Mechanical Properties and Torsional Friction Behaviors of Bogie Center Plate

In order to simulating the torsional friction of the center plate during the railcar body traveling on different railway curves at different environmental temperatures, the torsional friction behavior of monomer casting (MC) nylon composites which was used to make center plate, at temperatures of −25 °C to 50 °C was studied. With increasing temperature, the mechanical properties of nylon composites were weakened, whereas the visco-elastic property was boosted. Under torsional angle of 1.8 deg and 0.96 deg, all the torque–angular displacement (T–θ) curves exhibited the quasi-parallelogramic shape at various temperatures. When the temperature was higher than 25 °C under 0.42 deg, the shape transformed from elliptic to parallelogrammic. This indicated that the torsional regime changed from a partial slip to a gross slip. With increasing temperature, the torsional torque decreased and the wear mass loss increased because of weakened mechanical properties. The wear mechanism changed from slight plastic flow at low temperature to serious adhesive and three-body abrasion wear at high temperature.

Fabrication and properties of Ti–Zr–Ni quasicrystal and bulk composite materials by high pressure sintering

The overall composition of Ti40.83Zr40.83Ni18.34 quasicrystal powders that consist of the stable icosahedral phase (I-phase) was prepared by mechanical alloying and the subsequent heat treatment in a vacuum furnace. Then, bulk composite materials (BCMs) with the composition of Ti40.83Zr40.83Ni18.34 I-phase quasicrystal powders and carbonyl nickel powders as metal bonding agent (20wt.%), have been fabricated by high pressure sintering. The Vickers hardness, compressive strength, deformation at fracture, Young's modulus, and wear resistance of the BCMs have been studied in detail, after being sintered at different pressure and temperature. It indicates that high pressure sintering enables us to produce the BCMs (about 10mm in diameter and 3mm in height) with a short sintered time of 10min and high pressure of 3.0GPa. In addition, the optimum sintered condition is 3.0GPa-600°C, which is beneficial of the improvement of the performances of BCM, such as the Vickers hardness of 389, the compressive strength of 430MPa, the deformation at fracture of 2.20%, the Young's modulus of 19GPa, the lowest value of friction coefficient at 0.45±0.13, and wear mass losses of 0.24mm3. This work shows a promise in practical fabrication of BCM that consist of the stable Ti–Zr–Ni icosahedral quasicrystalline phase may be developed.

Sliding wear behavior of E-glass-epoxy/MWCNT composites: An experimental assessment

This investigation has evaluated the sliding wear properties of E-glass-epoxy/MWCNT (multiwalled carbon nanotube) composite and Epoxy/MWCNT composite. Four different reinforcements (0, 0.5,1 and 1.5 wt %) of MWCNTs are dispersed into an epoxy resin. Design of experiments (DOE) and Analysis of variance (ANOVA) are employed to understand the relationship between control factors (Percentage of reinforcement, Sliding distance, Sliding velocity and Normal load) and response measures (specific wear rate and friction coefficient). The control variables such as sliding distance (300, 600, 900 and 1200 m) and normal loads of 10, 15, 20 and 25 N and at sliding velocities of 1, 2, 3 and 4 m/s are chosen for this study. It is observed that that the specific wear rate and friction coefficient can be reduced by the addition of MWCNTs. Scanning electron microscopy (SEM) is used to observe the worn surfaces of the samples. Compared with neat epoxy, the composites with MWCNTs showed a lower mass loss, friction coefficient and wear rate and these parameters decreased with the increase of MWCNT percentage. Microscopic investigation of worn out sample fracture surface has revealed that fiber debonding happens when the stresses at the fiber matrix interface exceeds the interfacial strength, causing the fiber to debond from the matrix. The optimum control variables have been derived to reduce both wear and friction coefficient of composites.

Influence of laser alloying with boron and niobium on microstructure and properties of Nimonic 80A-alloy

Ni-base superalloys were widely used in aeronautics, chemical and petrochemical industries due to their high corrosion resistance, high creep and rupture strength at high temperature. However, these alloys were not considered for applications in which conditions of appreciable mechanical wear were predominant. The diffusion boriding provided suitable protection against wear. Unfortunately, this process required long duration and high temperature. In this study, instead of the diffusion process, the laser alloying with boron and niobium was used in order to produce the hard and wear resistant layer on Nimonic 80A-alloy. The laser-alloying was carried out as a two-step process. First, the external cylindrical surface of specimens was pre-placed with a paste containing boron and niobium. Then, the pre-placed coating and the thin surface layer of the substrate were re-melted by a laser beam. The high laser beam power (P=1.56kW) and high averaging irradiance (E=49.66kW/cm2) provided the thick laser re-melted zone. The laser-borided layers were significantly thicker (470µm) in comparison with the layers obtained as a consequence of the diffusion boriding. Simultaneously, the high overlapping of multiple laser tracks (86%) caused that the laser-alloyed layer was uniform in respect of the thickness. The produced layer consisted of nickel borides (Ni3B, Ni2B, Ni4B3, NiB), chromium borides (CrB, Cr2B), niobium borides (NbB2, NbB) and Ni-phase. The presence of hard borides caused the increase in microhardness up to 1000 HV in the re-melted zone. However, the measured values were lower than those-characteristic of niobium borides, chromium borides and nickel borides. The presence of the soft Ni-phase in re-melted zone was the reason for such a situation. After laser alloying, the significant increase in abrasive wear resistance was also observed. The mass wear intensity factor, as well as the relative mass loss of the laser-alloyed specimens, was over 10 times smaller in comparison with untreated Nimonic 80A-alloy.

Effect of Surface Properties Modification on Slurry Erosion–Corrosion Resistance of AISI 5117 Steel

The erosion–corrosion (E–C) wear behaviors of electroless nickel phosphorus (Ni-P) coating, carburizing and untreated low alloy steel AISI 5117 in water–sand slurry and saline–sand slurry were investigated using whirling-arm tester. The E–C wear mass loss was measured to evaluate the effect of mediums and surface modifications. The microstructure of carburizing and Ni-P coating was analyzed using an optical and scanning electron microscope (SEM) and X-ray diffraction (XRD) technique. Results showed that Ni-P coating and carburizing are effective in increasing wear resistance of low alloy steel. However, the Ni-P coating is more effective in increasing the E–C resistance. Also, the results showed that Ni-P coating, carburizing and untreated carbon steel behaved as ductile materials under erosion and E–C tests, and the maximum mass loss occurred at an impact angle of 45 deg. The synergism ratio was the lowest for the Ni-P coating, indicating that Ni-P coating improved an anti-E–C wear resistance.

Fretting-induced friction and wear in large flat-on-flat contact with quenched and tempered steel

Fretting may cause severe surface damage and lead to unexpected fatigue failure. Our test apparatus was designed based on reciprocating, large, annular flat-on-flat contact without any edge effects in the direction of the fretting movement. Fretting wear tests were run with quenched and tempered steel with different normal pressures and sliding amplitudes under gross sliding conditions. The development of the friction coefficient and total wear mass depended mostly on the accumulated sliding distance. Initially, friction and wear were highly adhesive but gradually changed to abrasive due to third body accumulation in the interface.

Ultrasonication-Induced Changes in Physicomechanical and Tribotechnical Properties of PTFE Composites

The effect of ultrasonication on PTFE and its composites with zeolite and fluoroplast F-4NTD-2 was studied. Ultrasonication was found to cause changes in the supramolecular structure, and consequently, the tensile strength, relative elongation, and mass wear rate. Changes in the topology of the materials following ultrasonication were investigated by scanning electron microscopy. The optimum enhancement of the desired properties was found in the PTFE composite containing 2% activated zeolite.

Experimental analysis of tribological behavior of UHMWPE against AISI420C and against TiAl6V4 alloy under dry and lubricated conditions

Friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against AISI420C austenitic stainless steel and against TiAl6V4 alloy under dry and lubricated conditions were investigated with a reciprocating pin-on-flat tribometer for comparative purposes. The tests were conducted by varying frequency of the pin alternative motion and the applied normal load. For the tests in lubricated conditions a fluid containing a large amount of sodium hyaluronate has been chosen. By using an electronic precision balance the wear mass loss of the UHMWPE samples was evaluated accordingly. Friction is greatly reduced by the presence of UHMWPE and this is believed to be due to the formation of a lubricating film of UHMWPE in the contact zone. Furthermore, the experimental investigation shows that the AISI420C/UHMWPE gives, in dry conditions, better values in the wear rate and in the friction coefficient than the TiAl6V4/UHMWPE.

Influence of Processing on the Microstructure and Properties of CoCrMoSi Alloy PTA Coatings

AbstractWear performance as well as the low toughness of CoCrMoSi alloys is associated with the presence of Laves phase. In light of this, alloying elements have been altered in order to reduce the brittleness of newly-cast alloys. This study evaluated coatings by Plasma Transferred Arc (PTA) with different interactions with the AISI 316L substrate. The higher the dilution, it was hypothesized, the higher Iron, Chromium and Nickel contents proceeding from substrate and, therefore, the lower hard Laves phase fraction. Coatings were characterized by light and scanning electron microscopy, X-ray diffraction and Vickers hardness. Wear behavior was assessed by pin-on-disc and ball-on-flat tests. Laves phase and Cobalt solid solution eutectic lamellar microstructure was observed for coating processed with 120A (18% dilution). The chemical composition was displaced to hypoeutectic, showing Cobalt solid solution dendrites and interdendrictic eutectic lamellar for the coatings processed with higher current intensity (150 / 180A), due to the higher interaction with the substrate (26 / 38% dilution). Dilution increased with the deposition current, causing hardness to decrease from 702 – 526 HV0.5. Wear mass loss rate increased by up to 41.7% and friction coefficient (μ) ranged from 0.45 – 1.06 as the chemical composition changed.

Formation of WC–Co coating by a novel technique of electrospark granules deposition

Abstract A novel scheme of electrospark deposition of hardening coatings on steel substrate is presented. According to it, the workpiece-substrate which must be coated is placed in the center of a hollow cylinder and filled with granules of WC–Co alloy. The current pulses are passed from the cylinder wall through granules to the cathode. Electrical discharges occur at the points of contact between the hard alloy particles and the cathode surface, and the coating forms on all surfaces of the workpiece simultaneously. This processing configuration is more productive and can facilitate the automation of the electrospark deposition (ESD) of coatings. In this paper, the influence of treatment duration and size of granule fractions on the mass transfer, structure, roughness, microhardness, and wear resistance of the coatings is investigated. It is shown that the obtained coatings have a structure and properties similar to those of traditional electrospark WC–Co coatings.

Friction and Wear of TiN–Si3N4 Nanocomposites Against ShKh15 Steel

Spark plasma sintering is used to produce dense silicon nitride nanoceramics with titanium nitride additions and nanofiber-strengthened composites. The sintered nanocomposites demonstrate quite high mechanical properties (HV ≈ 14–16 GPa, K Ic ≈ 4.8 MPa ∙ m 1/2 ) and low dry friction coefficient (f ≈ 0.65–0.68) and mass wear (~0.2–0.4 mg/km) against ShKh15 steel. The nanocomposite strengthened with 3.8 wt.% silicon nitride nanofibers shows the most balanced mechanical and tribotechnical characteristics.

Study on self-lubricating coating prepared by electrospark deposition

It is still a matter to get thick self-lubricating coating with good tribological properties and strong bond. In the present work, Cu/BN coating was produced by electrospark deposition on mild steel. Chemical compatibility of Cu/BN/steel was analysed. The effects of the electric capacitance and deposition time on coating performance were studied, and the microscopic morphologies and structure of the coating were analysed. The results showed that there were no reactions in Cu/BN/steel. With the increase in capacitance, the surface roughness, friction coefficient and wear mass loss all increased. With the increase in deposition time, the surface roughness increased. Scanning electron microscope images showed that the lubricating coating is smooth, and thick coating (∼100 μm) was formed with metallurgical bond.

The Tribological and Mechanical Properties of Pdcpd/Pew Composites Prepared by Reaction Injection Moulding

In order to improve mechanical performance and wear resistance of polydicyclopentadiene (PDCPD) by convenient methods and technologies, novel PDCPD/polyethylene wax (PEW) composites were prepared by in-situ polymerization in a simulated reaction injection moulding. Studies on the mechanical and tribological properties of the composites were carried out. The bending strength and hardness of PDCPD/PEW composites significantly improved compared with neat PDCPD. The incorporation of PEW in PDCPD greatly enhanced the wear resistance and reduced the friction coefficients. The wear mass loss and friction coefficients for PDCPD/ PEW composites decreased continuously in the range of our experiments. The SEM micrographs of the worn surface showed the friction and wear mechanism of PDCPD.

Synergistic Reinforcement of Phenol-Formaldehyde Resin Composites by Poly(Hexanedithiol)/Graphene Oxide

In this paper, the preparation of graphene oxide was achieved by Hummers method and the surface modification was achieved by poly(hexaneditiol), which was a synthetic thermotropic liquid crystalline polymer. The c-PHDT/GO/PF composites were prepared by blending, rolling and compression molding techniques. Then, the as-prepared samples were characterized by FTIR, Raman, XRD, TGA and POM to obtain information on their structures and properties. After that, the effects of c-PHDT/GO content on the mechanical properties, friction performance and dynamic mechanical performance of c-PHDT/GO/PF composites were studied by Mechanical and Dynamic Mechanical Analysis (DMA) methods. Also, Scanning Electron Microscope (SEM) was used for the characterization of wear and fracture surface morphology. The results revealed that the reinforcing effect of c-PHDT/GO was significant as a considerable enhancement on the mechanical performance of c-PHDT/GO/PF composite as compared to pure phenol-formaldehyde composites was observed: the impact strength, bending modulus and bending strength increased from 1.63 kJ/m2, 8.61 GPa and 41.55 MPa to 2.31 kJ/m2, 10.16 GPa and 54.40 MPa respectively at the c-PHDT/GO content = 0.75%. Moreover, the initial storage modulus increased by 28.4%, while the wear mass loss decreased by 17.8%. More importantly, the reinforcement by c-PHDT/GO was further enhanced as compared to GO/PF and p-PHDT/GO/PF composites, the impact strength of c-PHDT/GO/PF composite increased by 27.6% and 11.1%, the bending strength increased by 11.8% and 7.6%, the initial storage modulus increased by 16.2% and 4.2% and the mass loss due to wear decreased by 12.7% and 8.8%, respectively. Based on these results, we can conclude that the surface modification of GO by poly(hexanedithiol), which includes synergistic effect by c-PHDT and GO, improves the interfacial adhesion between GO and the resin matrix, thus reinforcing the composites.

The Influence of Plastic Deformation Performed before and after Electron Beam Irradiation on Mechanical Properties and Wear of UHMWPE

The paper compares the modification methods of polymers GUR 1050 and GUR 1020 by means of plastic deformation before (ON) and after (NO) irradiation with an electron beam (N). Evaluation of the effectiveness of the modification methods applied was carried out by means of micromechanical examinations and tribological tests on T-01 and T-05 testers (polymer/Vitalium alloy). The results of micromechanical, sclerometric and tribological tests indicate unequivocally the effectiveness of the modifications applied, as compared to the polymer modification through irradiation with an electron beam only. A decrease in hardness and elasticity modulus was found for materials subjected to the ON and NO technology as compared to N, while maintaining the growing trend of these values along with the applied radiation dose. There was also noted a large increase of the wear resistance coefficient, Wβ, and an increase of the microploughing component’s share in the wear mechanism β, which had a direct influence on the reduction of the linear wear by 2.5–3 times and a nearly twofold decrease of the mass wear. The surface subjected to friction processes became smoother and free of lamella fragments which were visible for the base material not subjected to any modifications. This was documented with the observations performed on a scanning microscope and in the stereometric examination of the surface.

Dry Sliding Wear Properties of HVOF Sprayed WC–10Co–4Cr Coating

The high-velocity oxygen-fuel (HVOF) spraying process was used to prepare WC–10Co–4Cr coating onto AISI 1045 steel substrate. The microstructure, hardness and dry sliding wear behavior of the coating were investigated and compared with cold work die steel Cr12MoV. The results showed that, the coating had low porosity, high microhardness, and homogeneous distribution of WC particles. The coating was composed of WC and W2C phases. With increase in load, the friction coefficients of the coating and the cold work die steel Cr12MoV decreased. The friction coefficients and wear mass losses of the coating were lower than that of the steel Cr12MoV. The dominant wear mechanism of the coating under both loads (30 and 50 N) was extrusion deformation and abrasion wear. For steel Cr12MoV, the dominant wear mechanism was plastic deformation and oxidation.

Effect of type, percentage and dispersion method of multi-walled carbon nanotubes on tribological properties of epoxy composites

In this work the wear behaviour of epoxy matrix composites with different types and percentages of multiwalled carbon nanotubes (MWCNTs) has been studied. Three different types (NC3100, NC3150 and NC3152) and percentages (0.1 and 0.5wt%) of MWCNTs were dispersed into an epoxy resin by a calendering process. The tribological properties of epoxy-MWCNTs nanocomposites were investigated using “pin-on disc” wear testing machine under different conditions (counterpart material, distances and sliding speeds test). Scanning electron microscopy and 3D optical profilometer were used to observe the worn surfaces of the samples. Compared with neat epoxy, the composites with MWCNTs showed a lower mass loss, friction coefficient and wear rate, and these parameters decreased with the increase of MWCNT percentage. Also, the results demonstrated that the epoxy composites with 0.5wt% of amino-MWCNT (NC3152) have the best tribological properties.

Gradient boride layers formed by diffusion carburizing and laser boriding

Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was sufficient, the diffusion borocarburized layer showed a better cohesion.

Tribological properties of aged nitrile butadiene rubber under dry sliding conditions

Nitrile Butadiene Rubber (NBR) is a polymer material and is widely used to make rubber-moving components in industrial applications. Ageing is an important factor that affects the friction and wear properties of the material. This study is aimed at investigating the tribological properties of NBR and how they are affected by ageing. The shore hardness, tensile strength and tear strength of normal and aged NBR samples were measured. A CBZ-1 tribo-tester was then used to conduct sliding wear tests between NBR pins and 1Cr18Ni9Ti stainless steel discs under dry sliding conditions. The surface morphologies of the worn NBR pins were examined using laser-interference profilometry and scanning electron microscopy. Also, the friction coefficients and wear rates were analysed and compared. The results showed that ageing had a significant effect on the mechanical and tribological properties of the NBR specimens. As the ageing time and temperature increased, the friction coefficient and the shore hardness also increased. Furthermore, accelerated ageing promoted the ageing process of NBR material, which resulted in a reduction in the tensile strength and tear strength of the NBR, along with the deterioration of its wear resistance. Consequently, its wear mass losses increased with the ageing process. The main wear mechanism between the rubbing pairs was found to be fatigue wear under dry conditions. The knowledge gained herein provides a better understanding of the material degradation and wear mechanism associated with ageing, and is useful for designing and selecting proper operation conditions for prolonged applications of the material under extreme circumstances.