Severe Abrasive Wear Research Articles

Tribological behaviour of 316L stainless steel additively manufactured by laser powder bed fusion and processed via high-pressure torsion

• The tribological behaviour of 316L SS fabricated by L-PBF and then processed by HPT was investigated. • HPT processing has led to the formation of nano-grained microstructures with significantly enhanced hardness. • Microscopy observations and wear parameter calculations indicate continuous improvement in wear performance after HPT processing. • The wear mechanisms were discussed by analysing the test material (316 L SS) and the countersurface (alumina ball). For the first time, the tribological behaviour of 316 L stainless steel (316 L SS) additively manufactured via laser powder bed fusion (L-PBF) with ultrafine- and nano-grains obtained from high-pressure torsion (HPT) processing has been investigated. The pin-on-disk dry sliding wear test results demonstrate enhancement wear performance after HPT processing, as indicated by the consistently lower coefficient of friction (COF), mass loss, m and specific wear rate, k values than the as-received state. The improvement in overall wear resistance could be attributed to the significantly high hardness obtained due to the nano-scale grain refinement with increasing torsional strains. Microscopy analysis suggests that the wear mechanism transitioned from severe abrasive wear before HPT to a combination of mild abrasive, adhesive, and tribo-oxidative wear after HPT.

Grain size dependent tribological behaviors of 700 °C annealed polycrystalline diamond

The role of original diamond grain size in the tribological behaviors of the 700 °C annealed polycrystalline diamond (PCD) is discussed in view of experimental studies using complementary analytical techniques (SEM&EDS, TGA-DSC, XRD and Raman). The original diamond grain size has a strong effect on the tribological behaviors of the annealed PCD, which can be accounted for by the various cobalt content and distribution shape. The annealed PCD with the original diamond grain size of 2 μm possesses the lowest cobalt content and presents severe abrasive wear, which is due to the plowing action of exfoliated diamond grains. During the annealing treatment of PCD with large original diamond grain, the large amount of leaf-like distributed cobalt facilitates the diamond graphitization by the catalytic action, which accelerates the formation of friction reducing carbonaceous transfer film, thus yields to a low friction coefficient. The fully oxidation filling into the spalling inhibits the serious grain exfoliation, thus further prevents the annealed PCD wearing substantially. Overall, the cobalt-catalytic diamond graphitization without an excessive wear resistance sacrifice can be exploited to achieve excellent tribological properties of PCD after 700 °C annealing treatment.

Effects of Heat Treatment Condition and Counter Materials on the Wear Behavior of Laser Direct Energy Deposited Fe-8Cr-3V-2Mo-2W Alloy

This study aimed to investigate the wear performance of laser direct energy deposited Fe-8Cr3V-2Mo-2W alloy under various wear environments, in terms of different heat treatment conditions. Ball on disk tribology tests were performed using high-carbon steel and zirconia balls as counter materials. The wear rates of the alloy depended significantly on both the wear sliding speed and the wear load. Microstructural observations of the worn surface and the wear debris indicated intensive tribo-oxidative wear that was presumably responsible for the strong dependency of the wear rate on the wear sliding speed. Regardless of the type of counter materials, the alloy in the as-built state had better wear performance than the alloy with heat treatments. Therefore, the use of the alloy without post heat treatment would be favorable to obtain long-term durability of the alloy in severe wear environments. The wear tests with two different counter materials of high-carbon steel and zirconia showed the high-carbon steel counter material had a higher wear rate than the zirconia. This was thought to be due to that strong third-body abrasive actions of the high-carbon steel counter material, evidenced by the severe abrasive wear of the counter material.

The effect of Si content on the structure and tribological performance of MoS2/Si coatings

In the present work, the synthesis of MoS2/Si coatings was conducted to study the effect of Si on the microstructure of the MoS2/Si coatings and their tribological behavior. With the adoption of advanced characterization methods, the results reveal that the introduction of Si plays significant roles in determining the morphologies and structures of the MoS2/Si coatings. The results demonstrate that the increase of Si content can cause the changes of the coatings from a typical porous with columnar morphology to a non-porous with featureless morphology, while as the Si content continues to increase up to a much higher content (i.e., 17.3 at.%) the coatings with composite structure change to the a multilayer nanostructure. The tribological tests results point out that the MoS2/Si coatings with a composite structure perform better tribological properties as the content of Si rises from 0 to 14.7 at.%, owing to the combination of the increase in hardness and the oxygen gettering effect of Si. However, the MoS2/Si coatings with a multilayer nanostructure formed under a much high Si content (17.3 at.% Si) display poor tribological properties as the excessive Si inhibits the formation of the transfer film upon severe three-body abrasive wear.

Investigation on the Microstructure and Wear Behavior of Laser-Cladded High Aluminum and Chromium Fe-B-C Coating.

In this study, a high aluminum and chromium Fe-B-C coating was prepared using laser cladding on 2Cr13 steel substrate. The microstructure, microhardness, and wear resistance of the high aluminum and chromium Fe-B-C coating were investigated. The results show that this dense coating possesses good metallurgical bond with the substrate. The microstructure is mainly composed of α-(Fe, Cr, Al) lath martensite, orthorhombic M2B boride, orthogonal M3C2, and orthorhombic M7C3 carbides. The microhardness of the coating can reach 620 HV which is 3.3-times higher than that (190 HV) of the substrate. The coating shows a lower friction coefficient of 0.75 than that of the substrate (1.08). The wear rates of the substrate and the coating are 0.295 mg/min and 0.103 mg/min, respectively, indicating the coating exhibits excellent wear resistance. The wear mechanism transforms severe adhesive wear and abrasive wear of the substrate to slight abrasive wear of the coating. The results can provide technical support to improve the properties of the Fe-based laser cladded coating.

High temperature tribological behaviors of aluminum matrix composites reinforced with solid lubricant particles

Abstract The AA6061−10wt.%B4C mono composite, AA6061−10wt.%B4C−Gr (Gr: graphite) hybrid composites containing 2.5, 5, and 7.5 wt.% Gr particles, and AA6061−10wt.%B4C−MoS2 hybrid composites containing 2.5, 5, and 7.5 wt.% MoS2 particles were fabricated through stir casting. The dry sliding tribological behaviors of the mono composite and hybrid composites were studied as a function of temperature on high temperature pin-on-disc tribotester against EN 31 counterface. The wear rate and friction coefficient of the Gr-reinforced and MoS2-reinforced hybrid composites decreased in the temperature range of 30−100 °C due to the combined lubrication offered by the wear protective layer and its solid lubricant phase. Scanning electron microscopy (SEM) observation of the worn pin surface revealed severe adhesion, delamination, and abrasion wear mechanisms at temperatures of 150, 200, and 250 °C, respectively. At 150 °C, transmission electron microscopy (TEM) observation of the hybrid composites revealed the formation of deformation bands due to severe plastic deformation and fine crystalline structure due to dynamic recrystallization.

Tribological performance and dry sliding-induced microstructure evolution in T20Z alloy under different atmospheric conditions

This study focused on the tribological performance and microstructure evolution of T20Z alloy after dry sliding in air and vacuum. After the tribological tests, normal load and sliding velocity were considered to be optimized based on specific wear rates using Taguchi technique. The results of S/N ratio showed that the optimization of the parameters was 10 N, 0.59 m s−1 for obtaining the minimum wear rates in both air and vacuum. Also, the worn surface and cross-section of T20Z alloy as well as wear debris and counterpart steel balls were analyzed by scanning electron microscopy. Raman spectrometer was performed to further analyze the worn surface. The topography of wear scar was observed using a three-dimensional optical profilometer. The microstructure evolution of T20Z alloy was analyzed by transmission electron microscopy. The results showed that the wear mechanisms in air varied from abrasive wear to delamination wear and severe abrasive wear, and the grain size was finally refined to nanoscale. In vacuum, however, wear mechanisms changed from slight abrasive wear to delamination wear and severe plastic deformation, and only the β phase was deformed.

Friction and wear of two polyethylenes under different tribological contact conditions

Tribological properties of ultrahigh-molecular weight polyethylene (UHMWPE) and cross-linked polyethylene (XLPE) were studied in two different wear modes. Firstly, reciprocating sliding wear studies under non-conformal contact investigated the effects of counterface surface roughness (polished, lapped and ground) of Ti6Al4V on the friction and wear of the polyethylenes. Secondly, two-body abrasive wear studies in conformal contact against different abrasive grit size papers were also carried out to ascertain the wear sensitivity of the polyethylenes under these adverse conditions. Wear mechanisms were studied using optical and scanning electron micrographs. The results of the reciprocating sliding wear studies showed that surface roughness of the counterface influenced friction and wear characteristics although no correlation was found between the coefficient of friction and specific wear rate. XLPE demonstrated wear sensitivity, particularly under severe abrasive wear condition. The results indicated that the performance of the polyethylenes greatly depends upon the tribological system under which it is operating.

Spark plasma sintering processed α−SiAlON bonded tungsten carbide: Densification, microstructure and tribomechanical properties

Processing, microstructure and tribomechanical performance of spark plasma sintering (SPS) processed α−SiAlON bonded tungsten carbide (WC) have been reported. SPS at 1750 °C under 40 MPa for 25 min resulted in almost theoretically dense composites. Microstructure analysis using scanning and transmission electron microscopy revealed formation of principally micron sized, equiaxed WC grains surrounded by sub-micron to micron sized α−SiAlON having both equiaxed (higher concentration) and elongated (lower concentration) grain morphology. Sharp and clean WC/α−SiAlON interface regions were noticed without any interfacial reaction product. As evidenced from elemental mapping under HAADF-STEM, the α−SiAlON grain boundary region was found to be rich in yttrium and oxygen, whereas, presence of characteristics elements were identified in α−SiAlON and WC grains. Addition of α−SiAlON in WC matrix resulted in progressive improvement in tribomechanical performance of the composites compared to pure WC. The 40 wt% α−SiAlON bonded WC matrix composite offered almost 30–33% higher Vickers hardness and toughness than those obtained for pure WC. Three point flexural strength of the 40 wt% α−SiAlON/WC composite was found to be around 425 MPa. Unlubricated wear tests also indicated significantly higher damage of hard and tough β−Si3N4 ball when sliding against the composites compared to pure WC. Formation of progressively thicker and adherent tribolayer containing broken particles of WC and α−SiAlON having sharp edges was possibly the primary reason that caused severe abrasive wear of the counterbody. Results indicated the efficacy of SPS processed α−SiAlON bonded WC composites having improved tribomechanical performance over conventional monolithic WC.

Duplex plasma treatment of AISI D2 tool steel by combining plasma nitriding (with and without white layer) and post-oxidation

AISI D2 tool steels are widely applicable in dies or tools manufacturing. Unfortunately, their use is drastically reduced due to short lifetime. Plasma nitriding without formation of white layer is an effective technique to improve the lifetime of tool steel by improving tribological features. Usually, white layer formation is unavoidable, thus its detrimental effects (its brittle nature causes severe abrasive wear) must be removed or reduced by some alternative treatment. Here, in this study, we attempted to investigate the effect of post-oxidation of nitrided tool steel with and without presence of white layer on its wear performance and its dynamic mechanical response. The micro-hardness and nano-hardness are enhanced by plasma nitriding, but a slight decrease with post-oxidation treatment. The post-oxidized samples show the formation of hematite and magnetite phases, which changes the wear mechanism of nitrided samples from abrasive to adhesive wear. This study suggests that the removal or avoidance of white layer formation is not compulsory, and its unfavorable effects on tribological performance of tool steel can be escaped by post-oxidation for a short time of 1 h. Analysis of contact stiffness and storage and loss moduli shows that the post-oxidation can result in surfaces less prone to cracking under cyclic loads. Duplex treatment by combining plasma nitriding and plasma oxidation is carried out in the same processing reactor by changing processing gasses admixture, thus it is favorable and economical for large scale industrial applications.

Tribological behavior of cold sprayed Inconel 718 coatings at room and elevated temperatures

In this study, Inconel 718 coatings were fabricated by high pressure cold spray deposition and the microstructure and tribological properties of the coatings were systematically investigated at both room and elevated temperatures. At the first place, the investigation on the effect of thermal exposure on the surface oxidation of the coatings was conducted in the absence of sliding. It was found that oxides started to form on the coating surface when the ambient temperature was above 500 °C. At 600 °C, a NiFe2O4 spinel oxide layer spread over the coating surface. Under sliding against an Al2O3 counter ball, oxides started to form on the coating surfaces in contact with the ball when the ambient temperature was above 200 °C due to the fact that the frictional and external heat had facilitated the formation of the oxides. Thus, the friction coefficients of the Inconel 718 coatings decreased with the increase of ambient temperatures. However, the wear rates of the coatings increased at 100 °C and 200 °C compared to those of the coatings tested at room temperature, which was due to the decrease of hardness and severe abrasive wear. When the ambient temperature was further increased to 300 °C, a transition in wear mechanism occurred and the wear rates decreased due to the formation and breakage of the surface oxides that could act as lubricants between the counter ball and coating. With further increase of ambient temperature, a ‘glaze’ layer was formed and grew on the wear tracks, which could act as a protective layer and showed a load-bearing effect that prevented further removal of the coating materials, resulting in an improved wear resistance of the Inconel 718 coatings at elevated temperatures. Therefore, cold sprayed Inconel 718 coatings could be potentially used under wear conditions at elevated temperatures.

A comparison study on wear characteristics of Ni-based, Co-based and Fe-based alloys for heated hot stamping tools manufactured by surfacing technology

To meet the demanding requirement of ultra-high-strength steel parts with tailored properties, heated hot stamping tools are becoming widely used. However, due to severe working conditions, wear on tool surface is serious. Therefore, the service life of heated hot stamping tools is limited. In this paper, with the purpose of improving the service life of heated hot stamping tools, we aim to find a suitable alloy with better wear-resistant properties to manufacture heated hot stamping tools by surfacing technology. Thus, wear comparison tests between SDCM steel and specimens made of Ni-based, Co-based and Fe-based alloys were conducted under 500 °C and 180 N normal load to determine which kind of alloy has the best wear-resistant properties. Specifically, the mechanical properties, worn volume, worn morphologies and wear mechanisms of test materials were investigated. The results indicate that the Fe-based alloy has the highest compressive yield strength and hardness, but the Co-based alloy has the lowest worn volume, which is 0.49 mm3 at 20 min and 0.70 mm3 at 90 min. And there is no obvious positive relationship between the mechanical properties and the wear-resistant properties of the test materials under the test conditions. The common wear characteristic of the four test materials is that their main wear mechanisms are oxidation wear. The Co-based alloy has the moderate mechanical properties, and its wear mechanisms are oxidation wear and adhesive wear; thus, shear tearing, material transfer and severe abrasive wear are avoided, and the oxide layers adhere to its worn surface instead of spalling. Therefore, the Co-based alloy manifests the best wear-resistant properties and is chosen as the surfacing materials for heated hot stamping tools.

Synergistic effect of talc/carbon spheres composite as oil‐based additive enhancing the lubricating properties for steel‐steel contact

AbstractTalc/carbon spheres (TC) composite was successfully fabricated through a simple and eco‐friendly hydrothermal method. The tribology properties of the base oil were significantly improved after adding TC composites, which had been studied by a ball on disc (BOD) tribometer. The friction coefficient of oil containing 0.5‐wt% TC composite (0.5 TC‐Oil) was only 0.08, with a decrease of 35.3% compared with the base oil at 5 N. Moreover, severe abrasive wear between friction pairs changed into slight plastic deformation lubricated with 0.5 TC‐Oil, as confirmed by scanning electron microscope (SEM). These results reflected notable synergy between self‐repair performance effect of talc and ball‐bearing effect of carbon spheres. The study displayed the potential lubricating performance of the TC composite in current generation oil lubricants.

Study of the welding procedure in nanostructured super-hard Fe- (Cr, Mo, W) - (C, B) hardfacing

The optimization of the tribological properties of the surfaces by means of hardfacing techniques has made great progress in the metallurgical field in recent times. Alloys of the Fe-Cr-C and Fe-C-B type present excellent wear performance under severe conditions, where the incorporation of Nb, Mo and W improves the performance of severe abrasive wear. In this context, new semi-automatic welding consumables have been designed that deposit iron base material of high alloy, with complex carboborides of W, Mo and Cr which present very high hardness and resistant to abrasive wear. The purpose of this work was to compare microstructural variations coupons welded with one or two layers, with or without shielding gas. The chemical composition was measured on each coupon, the microstructure was characterized by X-ray diffraction and scanning electron microscopy. Dilution percentage was determined and Vickers microhardness profiles (HV2) were made on the different phases (HV0.025). It was found that the dilution with and without shielding gas were 26% and 19%. The hardness was 960 and 1100 HV2. An increase in hardness was observed in the recrystallized areas, as well as a higher percentage of carboborides in the last bead.

Machining performances of TiN+AlCrN coated WC and Al2O3+TiC inserts for turning of AISI 4140 steel under dry condition

In this work, the machining performances of TiN + AlCrN coated tungsten carbide (WC) and Al2O3+TiC mixed ceramic inserts for turning of AISI 4140 steel were systematically evaluated by multivariate analysis of variance (MANOVA) with varying cutting speeds in the range of 150−220 m/min. MANOVA results showed that the averages surface roughness of workpiece and flank wear width of tool were significantly affected by the cutting speed, the type of inserts and their interaction at the significant level of 0.05. Additionally, the method of Bonferoni 95 % simultaneous confidence intervals for pairwise comparisons indicated that the cutting speed of 220 m/min was suitable for turning of AISI 4140 steel with both types of inserts. Microanalysis based on electron microscopy revealed that the Al2O3+TiC inserts experienced mild abrasion via microploughing, microcutting and microchipping while TiN + AlCrN coated WC ones got severe abrasive wear due to direct cutting and three-body abrasion.

Study on laser-induced oxidation modification coupled with micro milling of WC-Co cemented carbide

Cemented carbide is known as “industrial tooth” and has wide applications in terms of military, aerospace and other fields. In this study, a compound processing approach named laser-induced oxidation modification coupled with micro milling (LCMM) is proposed to solve its poor micro machining performance. The oxidation mechanism of WC-Co cemented carbide is revealed. Surface morphology and cross-section of WC-Co cemented carbide are investigated after laser irradiation under various average laser power and two reaction environment. Research results present that at the average power of 5 W, scanning speed of 0.5 mm/s and oxygen-rich oxygen condition, the laser-induced oxidation process is optimal. The thickness of oxide layer and sub-layer is 9.1 μm and 2.7 μm, and the material surface generates porous and loose oxide layer. In addition, comparative analyses are performed and discussed in detail considering milling force, tool wear and surface quality of machined micro slot. In comparison with conventional micro milling (CONM), cutting force of Fx and thrust force of Fy generated in removing the oxide layer in LCMM are reduced by 56% and 58% to maximum extent, respectively. The machined surface quality in LCMM is better than that in CONM with a slower rate of increase in surface roughness (Sa). At ap = 2 μm and fz = 1.5 μm/z, surface quality of machined micro slot in LCMM is superior to that at other milling parameters, and the surface roughness reach 57 nm. Tool wear rate in LCMM is greatly improved and tool wear mechanism mainly includes slight adhesion wear and abrasion wear. While, in CONM the wear mechanisms are severe abrasion wear, chipping and adhesion wear. The tool service life in LCMM can be promoted more than double.

Modified wear behavior of selective laser melted Ti6Al4V alloy by direct current assisted ultrasonic surface rolling process

Ti6Al4V alloy samples prepared by selective laser melting were treated by three different post-treatments: namely heat-treatment, ultrasonic surface rolling process (USRP) and direct current assisted ultrasonic surface rolling process (DC-USRP). Wear behaviors were evaluated using a block-on-disc rig under lubrication conditions. Results showed that the DC-USRP treated sample exhibited the lowest wear rate of 1 × 10−6 mm3 N−1 m−1, compared to that of the as-built (4 × 10−5 mm3 N−1 m−1), heat-treated (2 × 10−5 mm3 N−1 m−1) and USRP-treated samples (5 × 10−6 mm3 N−1 m−1). Consistent with changes in the wear rate, the friction coefficient was also gradually reduced. The as-built and heat-treated samples showed severe abrasive wear and delamination, while the USRP and DC-USRP treated samples displayed only mild abrasive wear. The improved wear resistance of the USRP and DC-USRP treated samples was attributed to the modified lubrication mechanism, increased hardness and compressive residual stress. Moreover, the wear resistance of the DC-USRP treated samples decreased with the increasing depth from the surface due to the effect of gradient work hardening.

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.

Abrasive Wear Resistance of Plasma-Nitrided Ti Enhanced by Ultrasonic Surface Rolling Processing Pre-Treatment.

The objective of the given work was to investigate abrasive wear behaviours of titanium (Ti) treated by ultrasonic surface rolling processing (USRP) pre-treatment and plasma nitriding (PN). Simulated lunar regolith particles (SLRPs) were employed as abrasive materials during characterization of tribological performances. The experimental results showed that SLRPs cause severe abrasive wear on Ti plasma-nitrided at 750 °C via the mechanism of micro-cutting. Due to the formation of a harder and thicker nitriding layer, the abrasive wear resistance of the Ti plasma-nitrided at 850 °C was enhanced, and its wear mechanism was mainly fatigue. USRP pre-treatment was effective at enhancing the abrasive wear resistance of plasma-nitrided Ti, due to the enhancement of the hardness and thickness of the nitride layer. Nevertheless, SLRPs significantly decreased the friction coefficient of Ti treated by USRP pre-treatment and PN, because the rolling of small granular abrasives impeded the adhesion of the worn surface. Furthermore, USRP pre-treatment also caused the formation of a dimpled surface with a large number of micropores which can hold wear debris during tribo-tests, and finally, polishing and rolling the wear debris resulted in a low friction coefficient (about 0.5).

Tribological properties of carbon fabric reinforced phenolic-based composites containing CNTs@MoS2 hybrids

Carbon fabric reinforced phenolic-based composites (CF/PF composites) often act a potential alternative to traditional materials which currently used in machine elements such as self-lubricating bearing, high-performance gears, and movable sealed. In the present study, the CNTs@MoS2 hybrids were synthesized by hydrothermal method, which were used as additives for their optimal wear resistance and lubricating properties in order to enhance the tribological properties of CF/PF composites. We found that the CF/PF composites with varying contents of CNTs@MoS2 hybrids showed improved self-lubricating properties under different sliding conditions, and the friction coefficient decreased as the content of additives increased. Nevertheless, the doping of 1 wt% hybrids decreased the wear resistance of CF/PF composites due to the occurrence of severe abrasive wear caused by peeling off of matrix in relatively large volume. However, with the contents of hybrids increased to 2 wt% and 4 wt%, the CF/PF composites exhibited improved wear resistance. The mechanism of wear resistance could be attributed to the excellent mechanical properties of CNTs and strong interfacial bonding force between hybrids and matrix as well as the formation of MoS2 transfer film on the surface of counterpart.