Abrasive Research Articles

Effect of Electrofriction Treatment on Microstructure, Corrosion Resistance and Wear Resistance of Cladding Coatings

In recent years, the issue of increasing the wear resistance of the working bodies of agricultural machinery designed for cutting and breaking the soil has received special attention. The surface layers of working bodies of agricultural machinery during operation are subjected to intensive abrasive wear, which leads to rapid wear of equipment and a reduction in its service life. The induction cladding method using materials such as Sormait-1 is widely used to increase the wear resistance of tool working surfaces. However, after coating, additional heat treatment is required to improve the physical and mechanical properties of the material and increase its durability. In electrofriction technology (EFT) hardening, the surfaces of the parts are subjected to melting under the influence of electric arcs. In this work, three types of surface treatment of L53 steel have been investigated: induction cladding using Sormait-1, electrofriction treatment, and a combination of induction cladding followed by electrofriction treatment. The microstructure was analyzed using optical microscopy and scanning electron microscopy. Erosion and abrasion tests were carried out in accordance with ASTM G65 and ASTM G76-04 international standards to evaluate the wear resistance of the materials under mechanical stress. A dendritic structure was formed after the induction cladding of the Sormait-1 material, but subsequent electrofriction treatment resulted in a reduction of this dendritic structure, which contributed to an increase in the hardness of the material. However, the highest hardness, reaching 965 HV, was recorded after electrofriction treatment of L53 steel. This is explained by needle martensite in the structure, which is formed as a result of quenching. Further, the influence of structural characteristics and hardness on erosion and abrasion wear resistance was examined. The analysis showed that the material microstructure and hardness have a decisive influence on the improvement of wear resistance, especially under conditions of intensive erosion and abrasive friction.

Understanding Electric Current Effects on Tribological Behaviors of Instantaneous Current-Carrying Pair With Recurrence Plot

Abstract Armature–rail instantaneous current-carrying friction in electromagnetic launchers refers to a sliding electric-mechanical impact friction and transition-induced arc erosion on a millisecond time scale. To reveal the electric current (50–300 A) effects on friction behavior and wear mechanism, the instantaneous current-carrying friction tests were performed with Al 1060 and Brass H62. Given the short nonlinear friction-induced signals, the friction behavior, including the time-domain information and system state, was comprehensively analyzed via frictional sound pressure (FSP), recurrence plot (RP), and recurrence quantification analysis (RQA). The wear topography was observed and characterized by the multifractal spectrum. Recurrence analyses demonstrate that as the current increases, the nonstationarity of the system state weakens, and the complexity and unpredictability enhance. Higher currents reduce the FSP amplitude, i.e., enhance the interfacial lubrication effect, but intensify electrical wear and surface roughness. This signifies a wear mechanism transition from abrasive wear and slight adhesive wear to arc ablation, fatigue wear, and severe adhesive wear. The widening spectrum width implies that the irregularity and fluctuation of the topography are enhanced with the current. RP patterns and RQA quantifiers correlate with the wear damage state. The results provide a reference for antiwear design and online degradation tracking of the rail.

Impact of tool nose size on the performance and wear behavior of carbide tool when boring 1Cr17Ni2 martensitic stainless-steel parts

Purpose This study aims to examine the cutting performance of a coated carbide tool during the boring of 1Cr17Ni2 martensitic stainless steel, with a focus on how the tool’s structural parameters, particularly the nose radius, affect the wear patterns, wear volume and lifetime of the cutting tool, and related mechanisms. Design/methodology/approach A full factorial boring experiment with three factors at two levels was conducted to analyze systematically the impact of cutting parameters on the tool wear behavior. The evolution of tool wear over the machining time was recorded, and the influences of the cutting parameters and nose radius on wear behavior of the tool were examined. Findings The results show that higher cutting parameters lead to significant wear or plastic deformation at the tool nose. When the cutting depth is less than the nose radius, the tool wear tends to be minimized. Larger nose radius tools have weaker chip-breaking but greater strength and wear resistance. Higher cutting parameters reduce wear for the tools with larger nose radius, maintaining their integrity. Wear mechanisms are primarily abrasive, adhesive and diffusion wear. Furthermore, the full-factorial analysis of variance revealed that for the tool with rε = 0.4 mm and 0.8 mm, the factors contributing the most to tool wear were cutting speed (38.76%) and cutting depth (86.43%), respectively. Originality/value This study is of great significance for selection of cutting tools and cutting parameters for boring 1Cr17Ni2 martensitic stainless-steel parts. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0266/

Microstructural, mechanical and wear behaviour of AA7075/ZrSiO4 surface composite developed via multi pass friction stir processing

ABSTRACT The microstructural, mechanical, and wear behaviour of the ZrSiO4-reinforced AA7075 surface composites fabricated through friction stir processing was analysed. The microstructure of the friction stir processed surface composite shows refined grain 52 μm, 20 μm and 5 μm after 1, 2 and 3 FSP pass which also leads to the uniform dispersion of reinforced ZrSiO4 particles in the A7075 surface as revealed by SEM, EDS, and XRD. The microhardness and tensile strength of the FSP surface composite were significantly improved by 35% and 54%, respectively, with the effect of ZrSiO4 particles, after six passes as compared to the substrate material. The slurry abrasive wear resistance of the surface composite after six FSP passes increased to 95% as compared to the A7075 substrate material. Similarly, the slurry erosive wear resistance was improved with increasing slurry rotating speed, but as slurry concentration increased at six passes, the wear rate decreased further due to self-colloids occurring between the slurry particles. Hence, slurry erosive wear resistance was increased by up to 220% as compared to substrate material. Hence, the novel fabrication of friction stir processed surface composite will be very beneficial for aerospace and marine structural components and the fabrication process is very robust and cost-efficient.

Formation of requirements for impact resistance and wear resistance of grinding balls

The article presents the results of a study of the operation processes of steel grinding balls in semi-autogenous grinding mills (SAG). It was determined that the balls experience both abrasive and impact loads. The properties of steel grinding balls with the same production technology are determined by the chemical composition and the formed microstructure over the entire cross-section of the ball. Balls made using 3 different technologies were studied. The balls of sets 1 and 2 show high hardness values at the surface, sufficient to ensure good resistance to wear during operation, and a sharp decrease in hardness at a distance of ~(15–20) mm from the surface as the volume of pearlite structures increases. At the same time, the balls of the 1st and 2nd sets showed low values of impact strength and insufficient resistance to impact. The lowest hardness values from the surface to the center were observed for set 3. Also, the highest mass loss during the abrasive wear test was recorded for set 3, which is explained by the lowest hardness values. The balls of set 3 showed higher values of impact strength and no splitting during the ball-on-ball test, which is explained by the soft ferrite-pearlite structure both on the surface and across the cross section of the ball, due to the reduced carbon content and the presence of nickel in the chemical composition. At the same time, the balls from set 3 showed the worst result in terms of abrasive wear. In the course of the conducted research, it was established that for successful operation in SAG, steel grinding balls must have a surface with high hardness due to the martensitic structure and a viscous core with a ferrite-pearlite structure. A promising direction in the development of technology for the production of steel grinding balls will be to obtain a steel ball microstructure that decreases uniformly from the surface to the center, which will allow maintaining high wear resistance and increasing the resistance to ball splitting

Tribological Properties of 7A04 Aluminum Alloy Enhanced by Ceramic Coating

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS2 composite coatings, and hard-anodized (HA) coatings on its surface. The friction and wear behaviors of these three coatings with diamond-like coated (DLC) rings under oil lubrication conditions were investigated using a ring–block friction tester. The wear rates of the coatings on the block surfaces were determined using laser confocal microscopy, and the wear trajectories of the coatings were examined using scanning electron microscopy. The results indicated that, among the three coatings, the MAO/MoS2 coating had the lowest coefficient of friction of 0.059, whereas the HA coating had the lowest wear rate of 1.47 × 10−6 mm/Nm. The MAO/MoS2 coatings exhibited excellent antifriction properties compared to the other coatings, whereas the HA coatings exhibited excellent anti-wear properties. The porous structure of the MAO coatings stored lubricant and replenished the lubrication film under oil lubrication. Meanwhile, the introduced MoS2 enhanced the densification of the coating and functioned as a solid lubricant. The HA coating exhibited good wear resistance owing to the dense structure of the amorphous-phase aluminum oxide. The mechanisms of abrasive and adhesive wear of the coatings under oil lubrication conditions and the optimization of the tribological properties by the solid–liquid synergistic lubrication effect were investigated. This study provides an effective method for the surface modification of Al alloys with potential applications in the aerospace and automotive industries.

Wear properties of Al6061/SiC + B4C + TiC hybrid composites produced by vacuum infiltration method

Abstract In the study, hybrid metal matrix composite (HMMC) structures were produced by vacuum infiltration method (VIM) using Al6061 alloy and varying amounts of SiC, B4C, and TiC ceramic powder pairs. Age-hardening processes were applied to these HMMCs. After heat treatment, wear behavior was examined under different loads using the pin-on-disc test method. All Al6061 hybrid composites exhibited better wear performance than unreinforced Al6061. In the wear tests of composite samples, the lowest volume loss and therefore the highest wear resistance were obtained in Al6061 3 wt.% B4C + SiC composites under 5 N force. The lowest wear resistance due to the highest volume loss was determined in Al6061/1 wt.% TiC + B4C composites under 15 N force. Abrasive and adhesive wear characteristics were observed in field emission scanning electron microscopy(FESEM) images of worn surfaces. Additionally, wear debris, smearing, and deep grove formations were determined on the surface. In the EDS analysis performed on the worn surface, O and Fe elements were found in addition to the elements that are likely to be in the structure (such as Al, B, C, Ti, Si, and Mg). The wear tests caused the formation of oxide layers on the sample surfaces.

Achieving considerable wear resistance in new Ti-based high-entropy alloys through microstructural hardening by adding Nb

In this study, (CoCrNiMn)78Ti22−xNbx eutectic high-entropy alloys were successfully synthesised via an arc melting process under vacuum, and the phase structure, microstructure, mechanical properties and dry sliding tribological behaviour of the alloys were systematically investigated. The XRD results for the (CoCrNiMn)78Ti22−xNbx eutectic high-entropy alloys are almost in agreement with the JMatPro phase diagram simulations, and the volume fraction of the Laves phase increased with increasing Nb content. OM and SEM images revealed that the microstructure was composed of dendrites (BCC A2) and interdendrites (BCC B2 +Laves) and changed from a hypoeutectic to a eutectic to a BCC B2 +Laves dual-phase structure, with the average grain size decreasing from 6.715 µm to 6.391 µm. Ti promoted the growth of the layered Laves phase and provided the alloy with base hardness and wear resistance. The hardness of the alloy combination of 21 % Ti and 1 % Nb reached the maximum value of 707.04 HV, whereas the average coefficient of friction (COF) and wear rate reached the lowest values of 0.49 and 1.668 × 10−4 mm3/N·m, respectively. With increasing load, the wear mechanism was mixed fatigue, delamination wear, and abrasive wear accompanied by oxidation, and the possibility of three-body wear paths between compacted tribolayers cannot be excluded. The debris was mostly in the form of microclusters, and the particle size range was concentrated between 1 −2 µm; meanwhile, the shape of the debris tended to develop from lamellar to spherical with increasing hardness.

Effect of Solution Aging Heat Treatment on Tribological Properties of Selective Laser Melted WC/18Ni300 Composite

Different contents of WC particle‐reinforced 18Ni300 composites are prepared by selective laser melting method, and the tribological properties are comparatively studied before and after solution aging heat treatment. The results show that a part of WC particles are dissolved, and no obvious pore defects appear. With the increase of WC content, the microstructure gradually transforms from cellular and fine columnar α‐Fe martensite to γ‐Fe austenite. After solution aging heat treatment, the phase is transformed into acicular martensite. The grain size significantly decreases, and the Vickers hardness increases. The grain size decreases and the hardness increases with increasing WC contents. For the as‐built composite, the friction coefficient first decreases and then increases, and the wear rate first increases and then decreases with the increase of WC content. With WC content increasing, the wear rate first decreases and then increases. After heat treatment, the tribological properties are improved. The groove of the specimens before heat treatment is deep with large delaminated craters, and the wear mechanism is dominated by adhesive and abrasive wear. The grooves become shallower, and the adhesive trace becomes lighter after heat treatment. The wear mechanism is mainly adhesive wear and abrasive wear, accompanying with oxidative wear.

Manufacturing Aluminum-Based Nanocomposites via Stir-Squeeze Casting Combined with Ultrasonication

This study successfully produced aluminum nanocomposites using a stir-squeeze casting process, both with and without ultrasonication (US) assistance. The matrix material utilized was scrap automobile wheel aluminum alloy (A356), with 1% SiC nano particles, averaging a size of 40 nm, serving as the reinforcement material. A comparison was made by also producing A356 aluminum casts with and without the use of US. The produced casts underwent thorough chemical and mechanical characterization, including optical and scanning microscopy, porosity measurement, hardness measurement, compression and tensile testing, as well as wear testing. Additionally, energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses were conducted to assess compositions and confirm the presence of SiC nano particles in the aluminum matrix. Porosity levels were slightly higher in the nanocomposite samples compared to pure matrix samples, attributed to the tendency of pore formation due to improper distribution of ceramic particles, resulting in clustering and agglomeration. However, significant reduction in porosity was observed with the application of ultrasonication, effectively breaking up clusters and agglomerations of reinforcement particles. Regarding mechanical properties, the A356+SiC sample with US exhibited the highest hardness (70.8 HRB), tensile strength (163.25 MPa), and compressive strength (387.2 MPa), along with the lowest abrasive wear loss (0.0017 g) among all types of casts produced in this study.

The Effect of DLC Surface Coatings on Microabrasive Wear of Ti-22Nb-6Zr Obtained by Powder Metallurgy

Titanium alloys have a high cost of production and exhibit low resistance to abrasive wear. The objective of this work was to carry out diamond-like carbon (DLC) coating, with dissimilar thicknesses, on Ti-22Nb-6Zr titanium alloys produced by powder metallurgy, and to evaluate its microabrasive wear resistance. The samples were compacted, cold pressed, and sintered, producing substrates for coating. The DLC coatings were carried out by PECVD (plasma-enhanced chemical vapor deposition). Free sphere microabrasive wear tests were performed using alumina (Al2O3) abrasive suspension. The DLC-coated samples were characterized by scanning electron microscopy (SEM), Vickers microhardness, coatings adhesion tests, confocal laser microscopy, atomic force microscopy (AFM), and Raman spectroscopy. The coatings did not show peeling-off or delamination in adhesion tests. The PECVD deposition was effective, producing sp2 and sp3 mixed carbon compounds characteristic of diamond-like carbon. The coatings provided good structural quality, homogeneity in surface roughness, excellent coating-to-substrate adhesion, and good tribological performance in microabrasive wear tests. The low wear coefficients obtained in this work demonstrate the excellent potential of DLC coatings to improve the tribological behavior of biocompatible titanium alloy parts (Ti-22Nb-6Zr) produced with a low modulus of elasticity (closer to the bone) and with near net shape, given by powder metallurgy processing.

The Exposure Height of Silicon Particle with Round Edges Effect on the Tribological Property of Al-Si Alloy Cylinder Liner

In order to improve the wear resistance of Al-Si alloy cylinder liners, surface treatment is usually used. The Al-Si alloy cylinder liner samples were prepared by mechanical grinding and laser finishing. The mechanical grinding samples were carried out by the independent design and development of a grinding machine. The laser finishing samples were laser-heated by a CO2 continuous transverse-flow laser. Both of the two surface treatments could provide the surfaces of protruding silicon particles with round edges to improve the wear resistance. However, in the exposure height of silicon particles with round edges, the study was lacking. The exposure height of silicon particles is important to the tribological properties of the Al-Si alloy cylinder liner, and should be analyzed in detail. The wear tests were completed by a contraposition reciprocating wear test rig under lubrication. It was found that when the silicon particles were exposed on the surface of the Al-Si alloy cylinder liner sample by 1.2 μm, the mechanical grinding samples and laser finishing samples all exhibited minimum friction coefficients and weight losses. This paper confirms that a suitable exposure height of silicon particles would reduce the probability of adhesion wear and abrasive wear of Al-Si alloy cylinder liners and increase the lubrication. It presents an excellent tribological property. However, when the exposure height of silicon particles is too high, the silicon particle is easily prone to plastic deformation or even falls off during the friction process due to the high stress and larger plastic contact index.

Sanding Performance and Wear Mechanism of Precision-Shaped Abrasive Belts for Medium-Density Fiberboard

Sanding in medium-density fiberboard (MDF) often encounters unstable quality and premature failure, primarily because there is currently no abrasive belt specifically suitable for MDF sanding characteristics. We designed two precision-shaped abrasive belts (PSAs) for MDF and herein report on the characteristics. The material removal process for PSA was divided into three phases; the most stable, phase II, represents the effective working period. Compared to the contrast accumulated abrasive belt, PSAs achieve 16.12 and 11.10 times higher surface quality based on the mean value of roughness parameter Sa, achieving 1.34- and 2.0-, and 15.61- and 8.54-times-higher stability in material removal and surface quality based on the mean deviation. Wear patterns on PSAs include large abrasive wear, micro-abrasive fall-off, fracture, and wear, avoiding premature failure due to blockage and promoting long-term and efficient sanding. The uniform shape, height, and distribution of particles in PSAs results in excellent sanding performance. This study provides the foundation for further research on sanding mechanisms and PSA design for MDF.

The STAP-Net: A new health perception and prediction framework for bearing-rotor systems under special working conditions

The health perception of bearing-rotor systems and their remaining useful life prediction has been a critical and challenging theme in the field of Prognostic and Health Management (PHM). Deep learning has become a prominent area of PHM research. However, current models have difficulty in adequately extracting the deep degradation characteristics of bearings and effectively capturing time-series information during the failure process. Also, most remaining useful life (RUL) prediction methods focus on point estimation, limiting their ability to quantify prediction uncertainty. To address these shortcomings, this study proposes a novel health perception and prediction framework, the Spatiotemporal Self-Attention Mechanism Probabilistic model (STAP-Net). The framework embodies the principles of lightweight design, focusing, and probabilistic approaches, and is tailored for bearing rotor systems operating under unique conditions. The key innovation of STAP-Net is the integration of a modified gate recurrent unit, known as the Weight Diminish Recurrent Unit (WDRU). It greatly reduces the training parameters of the proposed STAP-Net framework and improves the convergence speed of the framework while ensuring the prediction accuracy. Through analyzing the bearing-rotor system degradation data, the efficacy of STAP-Net is validated under special operating conditions such as misalignment and abrasive wear. The superior performance of the proposed framework is evaluated and confirmed based on 3 key metrics: high-precision point prediction, suitable prediction intervals, and reliable probabilistic prediction results.

Advanced Machine Learning and Experimental Studies of Polypropylene Based Polyesters Tribological Composite Systems for Sustainable Recycling Automation and Digitalization

Digitalization and automation are emerging solutions to the complex problems of recycling. In this research work, the experimental and Python based Archard deep learning wear rate models are introduced regarding recycling automation and composite tribological systems optimization. The optimum polyester fibers (PESF) of length of 3-3.5 mm were used for fabrication of polypropylene (PP)-PESF composite systems. The deformation, high texture, asperities, and micro-cracks were observed during scanning electron microscope and machine-learning studies. The lowest experimental value of abrasive wear of 3.0 × 10-6 mm3/Nm was observed for PP. Comparatively, higher experimental values of abrasive wear of the PP-PESF composites are found in the range of 4.35 × 10-6 to 4.7 × 10-6 mm3/Nm due to presence micro-defects on the surface of composites. The experimental values of Coefficient of friction (COF) of PP and PP-PESF are found in the range of 0.70 - 0.8 and 1.1 - 1.3, respectively. The experimental values of abrasive wear and COF are found compatible with literature. Similarly, the simulated values of abrasive wear of PP and PP-PESF composites are predicted in the range of 4.8×10-7 to 3.75×10-7 mm3/Nm, respectively. The predicted values of PP and PP-PESF composite show better resistance towards abrasive wear. The proposed experimental and simulated (in terms of Python coding, machine learning, image processing, artificial intelligence, and deep learning studies) research work can be introduced industrially for automation as well as digitalization of grinding of PES waste, processing, tribological testing, and SEM characterization evaluations.

Corrosion and wear mechanisms of rare earth (Gd, Sc, Y)-doped Zr-based amorphous alloys

Rare-earth elements have been utilized in the design and development of new amorphous alloys to improve the corrosion and wear resistance of Zr-based amorphous alloys. In this study, a rare-earth doped Zr-based amorphous alloy (Zr-BMG(RE)) was prepared by the copper mold casting method, which was investigated by corrosion and wear experiments. The results show that Zr-BMG(RE) has a completely amorphous structure, and the doping of rare earths Gd and Y raises the crystallization transition temperature of the amorphous. The addition of rare earth elements Gd and Sc increases the microhardness of Zr-based amorphous alloys, while rare earth element Y causes a slight decrease in microhardness. Gd and Sc will make Zr-based amorphous materials corrosion current density increases, the material pitting and localized corrosion, acid corrosion resistance is reduced. Y doping improves the self-corrosion potential of Zr-based amorphous alloys, reduces the corrosion current density, the surface passivation film is the densest, and the degree of charge transfer on the metal surface is the most difficult, Zr-BMG(Y) has a better corrosion resistance compared with other alloy materials. Zr-BMG(Gd) has the smallest friction rate (1.72×10-7mm3N-1mm-1), and the wear rates of the rare earth doped Zr-based amorphous alloys are all smaller than that of Zr-BMG, and the main loss mechanism of Zr-based amorphous alloys is the interaction of adhesive wear, abrasive wear, oxidative wear and fatigue wear. The mechanism of corrosion and wear resistance of rare earth to Zr-based amorphous alloys is discussed, which provides a new idea for the design of amorphous alloys.

Effects of Al variations on the microstructure and mechanical properties of laser-cladding AlxNbMo0.5Ti1.5Ta0.5Cr0.5 refractory high-entropy alloy coatings

Lightweight refractory high-entropy alloy coatings (RHEAcs) of AlXNbMo0.5Ti1.5Ta0.5Cr0.5 (where x = 0, 0.1, 0.2, and 0.3) were fabricated on 316L stainless steel surface by pre-placed powder laser cladding (LC) technology. The incorporation of Al element significantly enhanced the forming quality of coatings, resulting in nearly defect-free coatings with a thickness of 1.2-1.4mm. Microstructural analysis revealed that the coatings were primarily composed of body-centered cubic (BCC) solid solution and C15-Laves phase. Due to the influence of a single brittle BCC phase, the Al-free coating exhibited high strength and brittleness, leading to numerous defects caused by thermal stress. The introduction of Al element refined the microstructure and facilitated the formation of Laves phases at grain boundaries, thereby alleviating stress to a certain extent. Consequently, the microhardness of the RHEAcs was significantly higher than that of the substrate, with the Al-free coating achieving the highest microhardness of 1250 HV, which was 5.89 times that of the substrate. Wear resistance results indicated that, prior to annealing, RHEAcs with varying Al content outperformed 316L stainless steel. Post-annealing, the coatings exhibited significantly lower friction coefficients compared with the annealed 316L substrate. The Al-free coating showed significant accumulation of abrasive particles, leading to severe abrasive and oxidative wear. Conversely, post-annealing oxidation induced the formation of dense and directional oxide accumulation, resulting in a notable improvement in wear resistance. Finally, the underlying strengthening mechanisms have been proposed and analyzed.

Enhancing microstructure, nanomechanical and tribological properties of TiAl alloy processed by spark plasma sintering with Si3N4 ceramic particulates addition

TiAl matrix composites reinforced with varying weight fractions of Si3N4 ceramic particles were successfully fabricated by the spark plasma sintering method. The microstructure, nanomechanical and tribological properties of the sintered composites were investigated. The microstructural characterization revealed the evolution of a quasi-continuous and continuous network structure consisting of minor fractions of in-situ formed Ti2AlN, unreacted Si3N4 ceramic particles and dominant Ti5Si3 intermetallic phases within the TiAl matrix at Si3N4 content above 1.5 wt%. The in-situ precipitated phases enhanced the nanomechanical and tribological properties of the composites. The 7Si3N4/TiAl composite displayed the best nanomechanical properties, including nanohardness, elastic modulus, and H/Er ratio among the sintered samples. The specific wear rate of the composites decreases with increasing reinforcement content. 7Si3N4/TiAl composite exhibited the lowest specific wear rate of 0.38 ± 0.55 10-4 mm3/Nm, representing a 95.6% improvement in wear resistance compared to the unreinforced pure TiAl alloy. The improved wear performance of the composites was attributed to their load-bearing capacity and wear resistance of the hard, in-situ Ti2AlN, Ti5Si3 and unreacted Si3N4 particles in the TiAl matrix. The composites displayed a transition from adhesive wear to predominantly abrasive wear where the hard Si3N4 particles prevented direct metal-to-metal contact and facilitated the formation of a protective tribolayer, resulting in enhanced wear resistance. Hence, the developed Si3N4/TiAl composites are suitable for various structural and tribological applications.

Combined hybrid machining of laser ablation-drilling small holes in Cf/SiC composites

Carbon fiber-reinforced silicon carbide composite material (Cf/SiC) serves as a typical advanced material for fabricating hot-end components of aircraft engines. Its unique properties, including high hardness and anisotropy, pose significant challenges in processing. Nevertheless, a crucial structural element of hot-end components, specifically the cooling and heat dissipation holes, necessitates hole machining within the Cf/SiC composites. The intricate nature of machining this material often leads to compromised surface quality and severe wear on cutting tools during the hole machining process. This study delves into the feasibility of combined hybrid machining of laser ablation-drilling(L-DCM) for fabricating small holes in woven Cf/SiC composites, along with elucidating the underlying material removal mechanisms. The findings reveal approach significantly enhances the cutting performance of hard alloys tools when dealing with ceramic matrix composites. Notably, the wear mechanisms of the cutting tools primarily involve abrasive wear and adhesive wear. The primary processing defects observed in the small holes include fiber pullout at the entrance and exit, as well as material delamination at the exit, which are primarily attributed to debonding at the layer interface and brittle fracture of the matrix. The subsequent drilling process, conducted based on laser drilling, effectively eliminates thermal defects such as the heat-affected zone and recast layer, as well as morphological defects like taper. Additionally, this approach mitigates the tool wear process, minimizes the impact of compression effects on material removal, and enhances the shear action of the tool. Consequently, the layer interface remains securely bonded and intact after processing, thereby preserving the material's strength.

Investigate the impact wear failure behavior of CoMoCr engine valve and valve seat pairs under harsh conditions

The wear of sealing face is one of the main reasons for the failure of engine valve and valve seat pair. Changes in engine combustion load, running time, temperature, and other operating conditions can affect the wear of valve-valve seat pair. In this work, the CoMoCr alloy cladding valves and valve seat were used as the pair, to investigate the influencing mechanism of combustion load and valve lift on wear. Three groups of tests under different combinations of combustion loads and valve lifts were completed on self-designed testing rig. The results demonstrate that the increase of combustion load and valve lift exacerbate the wear of the valve and valve seat, and valve lift has a more significant effect on wear than combustion load. The increased combustion load worsens the microslip process and intensifies the abrasive wear process. Whereas valve lift enhances the impact process, causing the dense tribofilm on the material surface to delaminate due to fatigue. Destruction of the tribofilm prevented effective protection of the underlying material, which increased wear process.