Severe Adhesive Wear Research Articles

The tribology of Ag/MoS2-based self-lubricating laser claddings for high temperature forming of aluminium alloys

In recent years, the use of aluminium alloys in the automotive industry has gained significant attention due to their specific strength, corrosion resistance and recyclability. However, their forming at high temperature in processes like hot stamping is challenging due to the poor tribological behaviour of aluminium alloys, which is the source of severe adhesive wear and a poor surface quality of the finished product.In an effort to overcome these tribological problems, iron- and nickel-based self-lubricating laser claddings with the addition of solid lubricants such as silver and molybdenum disulfide have been evaluated under conditions representative of hot stamping against the aluminium alloy AA6082. It has been found that self-lubricating claddings decrease friction and counter body wear at high temperatures compared to alloys commonly used in forming tools such as grade 1.2367 steel. Furthermore, nickel-based self-lubricating claddings have shown a better tribological behaviour than their iron-based counterparts, due to the formation of a nickel-based sulfide layer on the counter body. It is thus expected that the implementation of self-lubricating claddings can improve the quality of the final product while reducing the need for added lubricant during the hot stamping of aluminium alloys.

Evolution of Bimodal Microstructure and High-Temperature Wear Resistance of Al-Cu-Ni Alloys

We report excellent high-temperature (300 °C) wear resistance of copper mold-cast Al80Cu15Ni5 and Al75Cu15Ni10 alloys. The evolution of a novel bimodal microstructure consisting of α-Al, eutectic α-Al + Al2Cu, and a vacancy ordered phase (Al3Ni2 type) restricts severe adhesive and abrasive wear at high temperature. Particularly, the Al75Cu15Ni10 alloy shows a low wear rate at 300 °C. In-depth microstructural characterization of the as-cast alloys and the worn samples elucidate the wear mechanism.

Tribological properties of soft/hard hybrid surface of Babbitt alloy/steel

PurposeBabbitt bush is easy to cause severe adhesive wear due to unexpected journal fall. This paper aims to improve wear resistance of Babbitt bush.Design/methodology/approachA soft/hard hybrid surface mircoprofile of Babbitt alloy/steel was fabricated by a technology of laser texture combined with hot-pressing. The friction and wear performances of bare steel (steel-h), Babbitt bush on steel (steel-s) and Babbitt filled in dimples of steel (steel-hs) were conducted on a ball-on-disc tester under dry and lubricated conditions.FindingsThe results showed that wettability of steel-hs was enhanced by forming soft/hard hybrid surface. Compared with steel-s, the stability of friction coefficient curve of steel-hs was improved without increasing coefficient friction. The wear resistance of steel-hs was remarkably enhanced under dry and lubricated conditions.Originality/valueThe originality of this paper is as following: to improve the tribological properties and to prolong service life of steel-s, soft/hard hybrid surface of Babbitt filled in dimples of steel substrate was successfully fabricated by laser texturing combined with hot-pressing. This paper showed that the lipophilicity of steel-hs was best among those of steel-s and steel-h. Babbitt alloy as a soft filler on dimples of steel substrate improved anti-wear of steel-s remarkably. It provides a new way to fabricate Babbitt as bushing on steel substrate.

Investigation on microstructures and mechanical behavior of in-situ synthesized TiC and TiB reinforced Ti6Al4V based composite

To enhance the friction and wear behavior of the Ti6Al4V alloy, titanium matrix composites (TMCs) were prepared by the single TiC, single TiB, and (TiC + TiB) hybrid reinforced with the volume fraction of 2, 6, and 10%, respectively. To investigate the effect of reinforcements on compressive and wear properties, the x-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electron Probe Micro-analyzer (EPMA), compression test, and pin-on-disk friction tests were applied. The results indicated that compressive strength increased with the addition of the reinforcement, and wear properties were improved due to the uniform distribution of reinforcements, which enhanced the resistance against tangential forces associated with the sliding wear. The wear mechanism appeared to be mainly based on the severe adhesive and oxidative wear, gradually transitioned to slight adhesion, abrasive, and oxidative wear.

SiC and Al surface cladding of Ti-6Al-4V for improved wear properties – The binary advantage

Ti-6Al-4V enjoys high specific strength, toughness and excellent corrosion resistance, but suffers high friction coefficient, severe adhesive wear and sensitivity to fretting wear. Laser surface cladding is one of the surface modification techniques used for improving on these demerits. Using a 4.4Kw continuous wave Nd-YAG laser processor, the surface cladding of as received Ti-6Al-4V alloy was done with mixtures of SiC and Al powders in different ratios. The SiC powder can serve as reinforcing particles and helps improve surface wear properties in resulting surface metal matrix composite while aluminium improves on the wetting between the metal and the reinforcement SiC phase. The success of this, however, depends on the careful optimisation of the powder ratio, which dictates the resulting phases and microstructural evolutions. Study of the cladding with scanning electron microscope (energy dispersive spectroscopy), optical microscope and x-ray diffraction revealed formation of intermetallic phases such as AlSiTi2, Ti7Al5Si12, TiSi2, AlSi3Ti2, Al6Ti19, Ti2VAl, AlTi3, AlCTi2, Ti3SiC2 and Ti5Si4, which should enhance micro-hardness and tribological properties of the surface relative to the bulk as-received alloy. 90:10 weight percentage ratio of SiC and Al powder mixture gave the best microhardness with a value of 1169.95 Hv, compared to 323.67 Hv of the as-received, and mass loss under abrasive wear tests was only 40% of the as received. The morphology obtained for the abraded surfaces is also indicative of this improvement. In carefully optimised proportions and laser condition, the binary combination of Al and SiC powders suffice for well improved Ti-6Al-4V surface properties.

Effect of surface self-nanocrystallization on friction and wear behavior of Al7075-T6511 alloy

Shot peening (SP) is an effective surface reinforced treatment, which can improve the surface properties of materials. Because of the poor wear resistance of aluminum alloys, the improvement of wear resistance has received more attention. In this research, Al7075-T6511 alloy was treated by the SP with different shot peening intensities to achieve the surface self-nanocrystallization and improve the dry friction and wear property. The surface microstructure of specimen before and after the SP was observed by using the optical microscope (OM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The surface roughness was examined by using laser confocal scanning microscope (CLSM). It has been found that the surface microhardness of the specimen was improved greatly after the SP. A nanocrystalline surface was generated, and the thickness of the severe plastic deformation layer increased with increase of the SP intensity. The results also show that the friction and wear mechanism of the SP-free specimen was severe adhesive wear and oxidation wear. While, the friction and wear mechanism of the SP-treated specimen was adhesive wear, accompanied with abrasive wear and oxidation wear.

Investigation of microstructure and mechanical properties of SiC/Al surface composites fabricated by friction stir processing

In this investigation, the surface aluminum matrix composites (SAMCs) was fabricated by four-pass friction stir processing (FSP) with SiC particles as the reinforcing phase and 1060 aluminum alloy as the matrix. The effects of FSP parameters on the microstructure, phase compositions and wear behavior of the SAMCs were investigated in detail. The bonding mechanism between Al and SiC was analyzed. The SiC particles have the best refinement and distribution results in the SAMCs when the rotational speed and traverse speed of the tool are 950 rpm and 60 mm min−1, respectively. The bonding between SiC and Al was the direct bonding by the mechanisms of diffusion and inlay. The microhardness and friction coefficient of the SAMCs were significantly affected by the size and distribution of the SiC particles. The maximum microhardness of the SAMCs is about 105 HV, which is approximately 4 times that of matrix. However, the lowest friction coefficient of SAMCs is about half of the matrix. The refined SiC particles and the excellent interfacial bonding between the SiC particles and the matrix changed the wear mechanism from severe adhesive wear to mild abrasive wear.

Improving the wear resistance of PTFE-based friction material used in ultrasonic motors by laser surface texturing

Abstract For improving wear resistance of PTFE-based material and performances of ultrasonic motors, 1-Dimple and 3-Dimple textures were fabricated on stator surface based on observations of transfer material. The worn surface and wear debris were observed to investigate the effect of textures on wear behavior. Meanwhile, performances of the motor were tested. The wear rate of PTFE material sliding against 3-Dimple stator decreased by 52.5%, the average speed of the motor was improved by 20.6%, and the maximum efficiency of 3-Dimple stator reached 32.7%. The beneficial effect of dimples was to make the contact surface discontinuous, thereby reducing the adhesion force between stator and PTFE material, which prevented severe adhesive wear of PTFE-based material and improved the motor performances.

Tribological behaviors in air and seawater of CrN/TiN superlattice coatings irradiated by high-intensity pulsed ion beam

Surface integrity and interface structure of coating materials play a key role in tribological and corrosion behaviors in harsh working environments in nuclear power plants. In this work, we focus on the investigations of tribological behaviors in air and seawater of CrN/TiN superlattice coatings deposited by the combined deep oscillation magnetron sputtering with pulsed dc magnetron sputtering, which were irradiated by high-intensity pulsed ion beam (HIPIB) with ion energy density of 1–3 J/cm2 and shot number of 1–5. At 1 J/cm2, the increased shot number leads to a broaden (111) peak of face-centered cubic crystal structure, indicating grain size refinement. At 3 J/cm2, the increased shot number results in the coarsening grain, and superlattice structure gradually disappeared at 2 shots, finally the coatings fell off from substrate at 5 shots. The highest hardness (H), H/E* (E*, effective Young’s modulus) and H3/E*2 of the coatings irradiated at 1 J/cm2 and 5 shots are achieved at 38.7 GPa, 0.1 and 0.387, respectively. The increased ion energy density and shot number result in the decrease in Rockwell C HF adhesion level from HF1 to HF6. At 1 Jcm−2 and 1 shot, tribological behavior of irradiated coatings in air was dominated by oxidative wear with coefficient of friction (COF) of 0.51 and specific wear rate of 4.2 × 10−7mm3N−1m−1. The irradiated coatings show excellent tribocorrosion properties in seawater with high open circuit potential of 0.32 V, low COF of 0.14 and specific tribocorrosion rate of 6.1 × 10−8mm3N−1m−1 without pitting corrosion under moderate HIPIB irradiation due to high surface integrity and stability of well-defined interfaces and dense microstructure. With an increase of energy density and shot number, wear mechanism in air changes to severe adhesive and oxidative wear, while tribocorrosion mechanism is gradually dominated by plough wear coupled with pitting corrosion.

Effect of Heat Treatment on Tribological Properties of Ni-B Coatings on Low Carbon Steel: Wear Maps and Wear Mechanisms

Among the alternatives for using low-carbon steel in parts with heavy wear, as gears and bearing surfaces, Ni-B electroless coatings deposited on these steels are considered due to their wear resistance. Wear maps, elaborated from friction or wear results found for different evaluated conditions, are a very useful tool for the selection of materials based on tribological properties. However, wear maps for electroless Ni-B coatings are very scarce. In this work, dry sliding wear tests with different loads and sliding velocities were performed on Ni-B electroless coatings applied on AISI/SAE 1018 steel, with and without heat treatment at 450 °C for 1 h, with the aim of determining the effect of the heat treatment on the friction coefficients and wear rates. Contour and profile maps, and finally friction and wear maps, were constructed for each of the coatings evaluated. The coating properties before and after the heat treatment were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), scratch tests, nanoindentation, and differential scanning calorimetry (DSC). Sliding wear tracks were studied using SEM, energy-dispersive spectroscopy (EDS), and micro-Raman spectroscopy. Good agreement between experimental and predicted values was found in friction and wear maps. Wear mechanisms change from flattening in less severe conditions to abrasion in more severe conditions, besides spalling and adhesive wear in untreated coatings. Moreover, abrasive wear is lower in heat-treated coating than in untreated coating.

Dry Sliding Behavior of a TiZr-Based Alloy under Air and Vacuum Conditions

In this study, dry sliding tribological properties of a TiZr-based alloy with the chemical composition Ti-20Zr-6.5Al-4V (wt.%) were tested in air and vacuum under different normal loads (10, 20, and 30 N) at various sliding velocities. Results showed that the coefficient of friction in air was lower than that in vacuum, whereas the wear volume at sliding velocity presented an opposite trend. The surfaces and cross-sectional morphology of wear scar on the TiZrAlV alloy was analyzed through scanning electron microscopy to determine the wear mechanisms. The observations showed that abrasive wear and delamination wear were dominant in air. In vacuum, the main wear mechanism changed from slightly abrasive and adhesive wear to severe adhesive wear and delamination wear as the normal load increased. Wear mechanism maps were also constructed and compared. The comparison showed that severe wear (including delamination wear) was prevalent in air.

Tribological performance of surface engineered low-cost beta titanium alloy

Low-cost beta (LCB) alloy (Ti-6.8Mo-4.5Fe-1.5Al) is developed specifically for non-aerospace (e.g. automotive and motor sports) applications. However, as for all other titanium alloys, LCB alloy is characterised by a high and unstable coefficient of friction and a strong scuffing tendency. Hence, a new surface engineering process based on optimal integration of bulk heat treatment with surface ceramic conversion has been developed, and this paper reports the tribological performance of surface engineered LBC titanium alloy. TEM analysis carried out on the microstructure of the ceramic conversion layer. Reciprocating pin-on-disc sliding wear tests were conducted against both WC and hardened steel balls under unlubricated and oil lubricated conditions. Post-examination of the wear tracks, counterparts and wear debris was carried out to investigate the wear mechanisms involved.The experimental results show that the wear resistance of the LCB alloy can be improved by 4–16 times by the novel combined bulk/surface treatment; the coefficient of friction is reduced from 0.8 to 1.0 for the untreated material to 0.2–0.4 for the treated samples. The wear mechanisms evolve from severe adhesive wear for the untreated material to mild abrasive wear for the treated material when sliding against a WC-Co ball in air. However, severe wear to the steel counterpart occurred and hence large frictional forces formed, which led to delamination wear of treated surfaces. It is also interesting to find that oil lubrication cannot reduce but rather increases the wear of treated surfaces especially when sliding against a hardened steel ball mainly due to oil pressure induced delamination wear.

Experimental Investigation on Direct Micro Milling of Cemented Carbide.

Cemented carbide is currently used for various precise molds and wear resistant parts. However, the machining of cemented carbide still is a difficult challenge due to its superior mechanical properties. In this paper, an experimental study was conducted on direct micro milling of cemented carbide with a polycrystalline diamond (PCD) micro end mill. The cutting force characteristics, surface formation, and tool wear mechanisms were systematically investigated. Experimental results show that cemented carbide can be removed with ductile cutting utilizing the PCD tool with a large tool tip radius. Micro burrs, brittle pits, and cracks are the observed surface damage mechanisms. The tool wear process presents microchipping on the cutting edge and exfoliating on the rake face in the early stage, and then severe abrasive and adhesive wear on the bottom face in the following stage.

Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces

Press hardened steels are commonly used as a lightweight choice for manufacturing car components because of the high ratio of strength to weight. The use of ultra-high-strength steels for the design of lightweight vehicles contributes to the reduction of emissions of carbon dioxide while maintaining passenger safety. Stamping tools used in press hardening processes suffer harsh contact conditions in terms of dramatic temperature changes, cyclic loadings, and complex interactions between coatings and oxidation. In mass production, tool wear is an inevitable problem that increases maintenance costs. Severe adhesive wear, also called galling, substantially occurs in the stamping tool used against Al—Si-coated workpieces. The galling that takes place during press hardening not only degrades the production quality but also shortens the service life of the tool. In order to properly arrange tool maintenance and minimize galling through adjusting process parameters, engineers need to know when and where galling occurs, based on modelling of the galling in press hardening simulations. In order to implement a galling simulation for press hardening, a modified Archard wear model is employed in the present study, which is a contact-mechanics-based model. The specific wear rate in the model is calibrated by the quantitative galling measurements of a high-temperature tribometer test. The tribological test is designed to mimic the press hardening conditions, where the correlations between galling and process parameters such as temperature, pressure, and sliding distance are outlined. The galling simulation is implemented in a full-scale press hardening experiment, and the predicted galling is validated in terms of severe galling positions and galling profiles. The galling profile evolution is correlated to variations in the contact conditions. Uncertainties in the numerical model, such as the choice of penalty scaling factor and friction coefficient, are analysed with a parameter study and discussed. This study demonstrates finite element (FE) simulations involving galling prediction in press hardening so as to improve product development and production efficiency.

Wear Resistance and Morphological Characterization of High-power Laser Clad Coatings on Ti-6Al-4V Alloy

Ti-Si binary coatings were cladded on Ti-6Al-4V alloy surface for improvement morphological orientation, microstructure and surface properties. The coatings were developed at 2.1 kW power, laser scanning speed of 1.2, 1.6 and 2.0 m/min, spot diameter of 3 mm and 0.5 overlap ratio. An optical microscope was used to magnify and analyse the microstructural arrangement and a microhardness indenter used to measure microhardness at 100gf for 10 seconds. The indent spacing was maintained at 100 µm between adjacent indents. The phase content of the coatings was analyzed with XRD technique. The coating wear resistance was tested at 10N force loading for 7 minutes using a TRB tribometer and characterized using SEM. Clad coatings were observed to exhibit refinement in microstructure with an increase in laser scanning speed where transformation occurred from equiaxed grains with localized smaller grains to refined grain structure. The highest degree of refinement was observed at 2.0 m/min scanning speed. It was also found that the microhardness property was improved by 2.44, 2.60 and 2.64 times the microhardness of Ti-6Al-4Vat 342.3 HV0.1. It is understood that high microhardness values favor improved wear resistance behavior. XRD analysis on the coatings revealed presence of Ti5Si3, Ti, Si and TiSi2 phases where Ti and Si are in matrix capacity and Ti5Si3 and TiSi2 present as intermetallic phases. The reported improvement in microhardness was attributed to the presence of Ti5Si3 and TiSi2. The action of the laser scanning speed was found to influence the clad height where an increase in laser scanning speed resulted in a decrease in clad height in the order 685.9, 491.4 and 291.5 µm for 1.2 m/min, 1.6 m/min and 2.0 m/min respectively. Wear test indicated that the coatings displayed an improved wear resistance by evidence of little material removal exhibited, compared to the substrate material which was dilapidated by severe adhesive wear and further aggravated by plastic deformation.

Effects of TiB2+TiC content on microstructure and wear resistance of Ni55-based composite coatings produced by plasma cladding

Abstract TiB2-TiC reinforced Ni55 matrix composite coatings were in-situ fabricated via plasma cladding on steels using Ti, B4C, and Ni55 as precursor materials at different proportions. Effects of TiB2+TiC content of ceramics phase on the microstructure and wear resistance were studied. The results showed that ceramic phases TiB2 and TiC were in-situ synthesized by plasma cladding, and the ceramic phase content significantly affected tribological performance and the wear mechanism of coatings under different loads. The composite ceramics protected coatings from further delamination wear by crack-resistance under a load of 30 N. Severe abrasive wear and adhesive wear were prevented when the load increased to 60 N because of the high hardness and strength of ceramic phases. Moreover, a compacted layer appeared on the wear surface of coatings with high content of ceramic phases, which effectively decreased the friction coefficient and wear rate. The TiB2-TiC composite ceramics significantly improved the wear performance of metal matrix composite coatings by different mechanisms under loads of 30 and 60 N.

Effect of Nitride Layer Thickness on Reciprocating Sliding Wear Behavior of AlN Layers on Spray-Formed Al Alloys

Dry sliding friction and wear behavior of nitrided and non-nitrided spray-formed Al alloys against AISI52100 steel were investigated using a linear-reciprocating ball on flat configuration under different normal loads. In case of nitrided spray-formed Al alloys, an increase in the applied normal load leads to a steady reduction of the stationary stage of the coefficient of friction depending on the sustainability of the AlN/Al compound. With regard to the nitride layer, thickness-specific wear regimes are distinguished for both spray-formed Al alloys. Nitrided spray-formed AlSi alloys show mild abrasive wear independent of normal load in case of AlN layers with up to 3 µm thickness. The layers exhibit an increased wear resistance compared to the non-nitrided condition for all applied test loads. Thick AlN layers > 4 µm show a steep increase in wear rate at loads exceeding 10 N, indicating a severe adhesive wear. These layers fail due to nitride layer delamination. Nitrided spray-formed AlMg alloys show mild abrasive wear for thin AlN layers < 4 µm up to normal loads of 12 N. Thick AlN layers almost immediately fail upon the initiation of the sliding contact due to crack formation within the nitride layer.

Development of High-Performance SiCp/Al-Si Composites by Equal Channel Angular Pressing

Relatively low compactness and unsatisfactory uniformity of reinforced particles severely restrict the performance and widespread industry applications of the powder metallurgy (PM) metal matrix composites (MMCs). Here, we developed a combined processing route of PM and equal channel angular pressing (ECAP) to enhance the mechanical properties and wear resistance of the SiCp/Al-Si composite. The results indicate that ECAP significantly refined the matrix grains, eliminated pores and promoted the uniformity of the reinforcement particles. After 8p-ECAP, the SiCp/Al-Si composite consisted of ultrafine Al matrix grains (600 nm) modified by uniformly-dispersed Si and SiCp particles, and the composite relative density approached 100%. The hardness and wear resistance of the 8p-ECAP SiCp/Al-Si composite were markedly improved compared to the PM composite. More ECAP passes continued a trend of improvement for the wear resistance and hardness. Moreover, while abrasion and delamination dominated the wear of PM composites, less severe adhesive wear and fatigue mechanisms played more important roles in the wear of PM-ECAP composites. This study demonstrates a new approach to designing wear-resistant Al-MMCs and is readily applicable to other Al-MMCs.

Microstructure and tribological properties of plasma sprayed TiCN-Mo based composite coatings

In the present work, TiCN-Mo composite coatings were fabricated by using reactive plasma spraying with the mixture of Ti-graphite aggregates and metal Mo powders under N2 condition. Results showed that metal Mo strips homogeneously dispersed in lamellar TiCN matrix to generate nearly alternate ceramic-metal composite coatings. Good interface bond were achieved between metal Mo strips and ceramic matrix due to the formation of rim structure. The Mo addition slightly decreased hardness of composite coatings. The hardness distribution uniformity of composite coatings also decreased as Mo content increased (>10 wt.%). TiCN-Mo composite coatings showed higher friction coefficient than coatings without Mo. TiCN-Mo composite coatings showed improved wear resistance with lower wear rate. Under present sliding wear condition, worn surfaces of TiCN based coatings were covered by thick iron and titanium oxide layer and wear debris contained large amount of oxides, indicating severe adhesive wear accompanied with oxidative wear.

Preparation and tribological properties of MoS2/graphite composite coatings modified by La2O3

PurposeThe MoS2/graphite composite coatings modified by La2O3 through spraying technique were successfully prepared on the inner rings of spherical plain bearings. As a comparison, unmodified coatings were also prepared. This paper aims to study the La-modified MoS2/graphite composite coating experimentally and improve the tribological performance of self-lubricating spherical plain bearings.Design/methodology/approachThe performance of La2O3 toward the friction coefficient, temperature rise and wear rate of the coatings was studied by a self-made tribo-tester under different swing cycles. And the texture, surface morphology and element composition of the coatings were characterized by scanning electron microscope, energy dispersive spectroscopy and X-ray diffractometry.FindingsThe additives La2O3 refined the coatings’ microstructure and improved the tribological properties of the coatings. The oxidation of Mo + 4 to Mo + 6 was effectively inhibited. And the amount of abrasive grains, peeling pits and local cracks on the coatings surface decreased and homogeneous lubricating films formed, which were attributed to the existence of La2O3. The wear mechanisms of unmodified coatings were severe abrasive wear, adhesive wear and delamination wear. However, it exhibited superior wear resistance of the La-modified coatings to unmodified coatings, presenting slight abrasive wear and adhesive wear. The service life of bearings was prolonged under the protection of the modified coatings.Originality/valueThe paper proposed a new modified MoS2/Graphite composite coating for the self-lubricating spherical plain bearings. The investigation on the friction, wear and temperature increase behaviors and the wear mechanisms of the coatings are beneficial to prolonging the service life of the self-lubricating spherical plain bearings.