Some aspects of solid particle erosion of cermets

The erosive wear resistance of cermets with different composition, structure and properties has been investigated. It was shown that the erosive wear resistance of cermets can not be estimated only by hardness, characterizing resistance to penetration. The differences in wear resistance between cermet materials with equal hardness levels can be attributed to differences in their resistance to fracture and fracture toughness. The mechanism of erosion depends first on testing conditions. The present paper discusses some features of the material removal process during particle-wall collision. Systematic studies of the influence of the impact variables on the collision process have been carried out.     

Sand–water slurry erosion of API 5L X65 pipe steel as quenched from intercritical temperature

The objective of this study was to analyse the erosion of API 5L X65 pipe steel whose microstructure consisted of ferrite and martensite obtained by quenching from intercritical temperature (770°C). Jet impingement tests with sand–water slurry were used. The changes in mechanical properties, caused by heat treatment carried out, did not induce changes in either the mechanism or erosion resistance. The erosion rate increased with angle of attack until 30° and later decreased until 90°. The microtexture of the eroded surfaces, at angles of attack of 30° and 90°, were similar for both conditions and were composed of craters and platelets at several stages of evolution. The erosion mechanism was by extrusion with the forming and forging of platelets.     

Correlation between solid particle erosion of cermets and particle impact dynamics

Since the erosion rate depends on energy exchange between particle and material, a reformulation and solution of the equations of two solid bodies collision is presented and adapted to the calculation of the energy absorbed by a material surface during impact of a spherical particle onto a plain target. It has been observed that energy loss is a strong function of dynamic coefficients named as coefficient of velocity restitution after impact, k, and coefficient of dynamic friction, f. The new method and experimental equipment for the coefficients determination are described. It was shown that energy consumption during application may be an appropriate guide for the material selection in the conditions of erosive wear.     

Solid particle erosion of unidirectional fibre reinforced thermoplastic composites

In the present study, the solid particle erosion behaviour of neat PEEK matrix and unidirectional glass fibre (GF) and carbon fibre (CF) reinforced polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) composites has been studied. The erosion experiments have been carried out by using silica sand particles (200 ± 50 μm) as an erodent. Steady state erosion rates of these composites have been evaluated at different impact angles and impact velocities. The neat PEEK exhibited peak erosion rate at 30° impingement angle whereas the composites exhibited a semi-ductile behaviour with peak erosion rate at 60° impact angle. The erosion rate of the glass fibre reinforced composites was higher than that of the carbon fibre reinforced composites. The results show that the fibre orientation has a significant influence on erosion rate only at lower impact angles. The erosion rate of the composites was higher when the particles impact perpendicular to the fibre direction than parallel to the fibres. The morphology of eroded surfaces was observed under scanning electron microscope and damage mechanisms were discussed.     

Abrasive erosive wear of powder steels and cermets

Composite materials produced by powder metallurgy provide solutions to many engineering applications that require materials with high abrasive wear resistance. The actual wear behaviour of a material is associated with many external factors (abrasive particle size, velocity and angularity) and intrinsic material properties of wear (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of wear resistant materials are highly dependent on the content of the reinforcing phase, its size and on the mechanical properties of the constituent phase. This study is focused on the analysis of the (AEW) abrasive erosive wear (solid particle erosion) using different wear devices and abrasives. Powder materials (steels, cermets and hardmetals) were studied. Wear resistance of materials and wear mechanisms were studied and compared with those of commercial steels. Based on the results of wear studies, surface degradation mechanisms are proposed. The following parameters characterizing the materials were found necessary in materials creation and selection: hardness (preferably in scale comparable with impact), type of structure (preferably hardmetal type) and wear parameters characterizing material removal at plastic deformation.     

High temperature erosion of Ti(Mo)C–Ni cermets

The resistance of Ti(Mo)C–Ni cermets of different binder content to solid particle erosion was evaluated at 25, 350 and 650 °C. The elevated temperature erosion of cermets containing 40, 50, 60, 70 and 80 wt.% of titanium carbides and produced from the powder of initially different ratios of Ni to Mo were tested with the help of specially designed centrifugal particle accelerator using silica as the abrasive. Erosion rate was related to both microstructure developed during sintering and materials removal mechanisms operating at the test conditions (impact angle of particles jet was 30° and 90° and velocity was 50 ms⁻¹). The erosion rate decreases with the increase of TiC and Mo contents in the composite. At 650 °C the process of tribo-oxidation affected the material performance to a great extent. The morphology of the worn surface was analyzed with SEM to determine the erosion mechanisms.     

Experimental verification of a model of erosion due to the impact of rigid single angular particles on fully plastic targets

A previously described rigid-plastic model of the erosion of ductile targets by the impact of single angular particles was experimentally verified over a wide range of particle angularities, incident angles of attack, and incident orientation angles. The model assumes that the particle is perfectly rigid and thus is non-deforming, while the target material response is fully plastic, so that elastic rebound effects are neglected.Measurements of particle rebound kinematics, crater volume, and crater shape revealed generally good agreement with those predicted by the rigid-plastic model, and erosion mechanisms resulting from particles tumbling either forwards or backwards, were identified. For highly angular particles, target material removal sometimes occurred due to tunnelling of the particles below the target surface, leading to early break-off of a machined chip, behaviour that could not be predicted by the rigid-plastic model. Besides providing insights into fundamental erosion mechanisms, the results of the present study can be used to predict particle rebound kinematics, crucial for simulations of erosive streams which take into account interference between incident and rebounding particles.     

The anti-slurry erosion properties of polyethylene for sewerage pipe use

Sewerage systems are more common in Japan. The pipes and fittings in the systems are exposed not only to a corrosive environment, but also to the impact by solid particles contained in mud drains, resulting in an erosive wear on the surface. A strategy for coping with these problems involves replacing the more traditionally used iron and steel pipes with polymeric materials, which have excellent anti-corrosion properties. In this study, a slurry erosion test were carried out using a jet-in-slit apparatus on seven types of polyethylenes, three other types of polymers, and two types of iron and steels, thoroughly taking into account the fact that erosion damage is highly dependent on the impact angle of the particles. As a result, all the polyethylenes proved to have excellent anti-erosion properties, compared with the other materials over the entire range of particle impact angle. Further, a model was proposed to account the impact angle dependency of the erosion damage. The model aided in clarifying the reasons why the erosion rate of the polyethylenes is satisfactorily correlated with a complex parameter in which the fracture energy and the elastic modulus are combined.     

Effect of structural features on erosion resistance of cast irons

Erosion resistance of four types of cast iron of different microstructures and graphite morphologies (viz., grey cast iron, compacted graphite iron, spheroidal graphite iron and austempered ductile iron) was evaluated in three different erosive media. Results indicate that austempered ductile iron has the highest erosion resistance in all three media, followed by spheroidal graphite iron, compacted graphite iron and grey cast iron, in that order. Graphite morphology has a significant effect on the erosion resistance of these irons in quartz-water and iron oxide-oil slurry. However, the matrix microstructure determines the erosion resistance of these irons in quartz-oil slurry. The parameter H/E (which is the ratio of the Brinell hardness number to Young's modulus of the material) has been found to be a good indicator of erosive wear in quartz-oil slurry.     

Solid particle erosion behaviour of Ti6Al4V alloy

Abstract

The effects of particle impingement angle, impingement velocity and erodent particle size on the erosion rate and surface morphology of the Ti6Al4V alloy have been investigated comprehensively in order to evaluate solid particle erosion behaviour of Ti6Al4V alloy. Samples were eroded in a specially designed sandblasting system under various parameters using alumina (Al₂O₃) erodent particles. Surface morphology investigations were examined by scanning electron microscope using various analysis and modes (energy dispersive X-ray analysis, elemental mapping and compositional contrast). Ti6Al4V alloy showed ductile behaviour with a maximum erosion rate at 30° impingement angle. Erosion rate of Ti6Al4V alloy increased with increases in velocity and decreased with increases in erodent particle size. Scanning electron microscopy investigations of eroded surfaces of Ti6Al4V alloy samples reveal the dominant erosion mechanism such as microploughing, microcutting and plastic deformation. Embedded erodent particles on the surfaces of Ti6Al4V alloy nearly at all particle impingement angles and velocities were clearly detected.     

Solid particle erosion behaviour of metallic materials at room and elevated temperatures

The behaviour of metallic materials subjected to solid particle erosion has been studied extensively over the last few decades. It is not the purpose of this paper to provide a comprehensive review of the above body of work especially since many such reviews already exist. Rather, the aim of this paper is to describe briefly the salient features characteristic of room temperature and elevated temperature erosion of metallic materials and follow it up with a review of some of the recent results, which in our opinion, have enhanced our current understanding in the area of solid particle erosion of metallic materials. As a natural consequence, the paper concludes with a critical review of the areas which require further study.     

激光处理对人牙釉质酸蚀和耐磨性能的影响

以人牙釉质为研究对象,对牙釉质表面进行激光处理,对激光处理前后牙釉质的表面形貌、力学性能和耐磨性能进行分析,旨在探索激光处理对牙齿酸蚀的抑制和修复作用,为激光在牙齿酸蚀抑制方面的临床应用提供理论指导。结果表明,原始牙釉质表面和酸蚀牙釉质表面经激光处理后,其表面硬度均显著提高、抗酸蚀能力增强;但是,激光处理会导致牙釉质表面变得粗糙,出现大量裂纹和孔洞,牙齿表面的弹性模量降低,表面脆性增大,从而使得牙齿耐磨性显著降低,造成的损伤重于酸蚀。     

固体自润滑涂层摩擦磨损特性研究

随着机械加工技术和空间技术的发展,固体润滑涂层在比较恶劣的润滑环境下能起到独特的润滑效果,得到高速发展和广泛应用.在综合国内外研究和报道的基础上,对一般固体润滑涂层和纳米固体润滑涂层的摩擦磨损特性的研究现状进行归纳,指出固体润滑涂层摩擦磨损研究的发展方向.     

Investigation of impact of solid particles against hardmetal and cermet targets

The objective of the present work is to investigate and discuss some features of the surface damage and material removal process during particle-wall collision of the solid particles and hardmetal and cermet targets. The restitution parameters of TiC-base cermets, WC–Co hardmetals and glass of different composition and properties have been investigated. In order to clarify the details of the impact of glass spheres and corundum particles of irregular shape on a solid half-space, the process of interaction of solid particle with target was studied using a Laser Doppler Anemometer (LDA) measuring technique. Targets were impacted with particles over the range of impact velocities (7–50 m s⁻¹) at impact angle 67°. The experimentally observed variations of the coefficient of velocity restitution as a function of the test material properties, impact velocity and hardness ratio (H_m/H_a) are adequately explained on the basis of a theoretical model. Systematic studies of the influence of the impact variables on the collision process have been carried out.     

Mechanical and tribological properties of short-fiber-reinforced SiC composites

The short-carbon-fiber-reinforced SiC (C_sf/SiC) composites were prepared by hot-pressing sintering with Si, Al and B as sintering additives. The effects of fiber volume fraction on the mechanical and tribological properties of the C_sf/SiC composites were investigated. The results show that the bending strength values of the composites containing a certain content of the short carbon fibers are higher than that of the monolithic SiC. The friction coefficients of the composites decrease with increasing short carbon fibers content. Except of the composite containing 53 vol% short carbon fibers, the wear rates of the composites decrease with increasing short carbon fibers content, and are lower than that of the monolithic SiC drastically.     

Wear properties of two-phase Al2O3/ZrO2 (Y2O3) ceramics at temperatures from 296 to 1073 K

Reciprocating sliding friction experiments were conducted with various two-phase, directionally solidified Al₂O₃/ZrO₂ (Y₂O₃) pins sliding on B₄C flats in air at temperatures of 296, 873, and 1073 K under dry sliding conditions. Results indicate that all the Al₂O₃/ZrO₂ (Y₂O₃) ceramics, from highly Al₂O₃-rich to ZrO₂-rich, exceed the main wear criterion requirement of 10⁻⁶ mm³ N⁻¹ m⁻¹ or lower for effective wear-resistant applications. Particularly, the eutectics and Al₂O₃-rich ceramics showed superior wear properties. The composition and microstructure of Al₂O₃/ZrO₂ (Y₂O₃) ceramics played a dominant role in controlling the wear and friction properties. The controlling mechanism of the ceramic wear, friction, and hardness was an intrinsic effect involving the resistance to shear fracture of heterophase bonding and cohesive bonding and the interlocking microstructures at different scales in the ceramics.     

A correlation between the tribological and mechanical properties of short carbon fibers reinforced PEEK materials with different fiber orientations

In this work the effect of fiber orientation on the mechanical and tribological properties of SCF (short carbon fibers)/PTFE (poly-tetra-fluor-ethylene)/graphite filled PEEK (poly-ether-ether-keton) composites was studied. The composites were manufactured by using injection molding technique. Mechanical and tribological experiments were conducted to measure the compression modulus, compression strength and wear resistance. A correlation of the tribological and mechanical properties considering different fiber orientations was studied. Additionally to the fiber orientation influence, the wear resistance under low and high pressures was examined. The results analyses, based on scratch experiments and scanning electron microscope (SEM) inspections explain how the fiber orientation influences the mechanical performance and the tribological properties of the considered materials.     

The erosion and abrasion characteristics of alumina coatings plasma sprayed under different spraying conditions

A series of plasma sprayed alumina coatings was evaluated regarding their erosion and abrasion characteristics. The coatings were deposited under different spraying conditions, using a commercial axial injection plasma spray system, and with powders of different grit sizes and crystallinity. A sintered bulk alumina and a conventionally sprayed coating, produced by a radial injection air plasma spray technique, were tested as reference materials. To evaluate the importance of energy input the coatings were produced using two different torch nozzle sizes and gas mixtures with a varied amount of hydrogen. The erosion and abrasion results indicate that hydrogen concentration, nozzle size and precursor powder type and size influence the tribological characteristics of the coatings. The wear resistance of the coatings seems to benefit from an increase in hydrogen concentration or torch nozzle size. The effect of precursor powder size on the wear resistance was more complex but indicates that sapphire powders of medium precursor sizes are advantageous to ordinary plasma spraying powders of alumina.     

Solid particle erosion behaviour of glass fibre reinforced boric acid filled epoxy resin composites

The tests which involved angular aluminium (Al₂O₃) particles with two different sizes of approximately 200 and 400 μm were conducted at the operating conditions namely different impact velocities of approximately 23, 34 and 53 m/s, two different fibre directions [0° (0/90) and 45° (45/−45)] and three different impingement angles of 30°, 60° and 90°. New composites with addition of Boric Acid filler material at 15% of resin exhibited upper wear than the neat materials without filler material. This means the filler material has decreased the erosion wear resistance. SEM views showing worn out surfaces of the test specimens were scrutinised.     

Dry sliding wear properties of unhybrid and hybrid Al alloy based nanocomposites

Abstract

Nanosize B₄C and/or MoS₂ particles reinforced AA2219 alloy composites were prepared using the stir casting process. The wear properties were evaluated for several speed (3.14–5.65 m s^?1), load (10–50 N) and distance (0–2500 m) conditions. The nanoparticles dispersion, density, wear resistance, morphology of the worn surface and loose wear debris were discussed in detail. The wear resistance improvement results by nanoparticle addition correspond well with the hardness. Between the nanocomposites, hybrid composites show significantly higher wear resistance for all load, speed and sliding distance conditions. The better wear resistance is attributed to the matrix strengthening by nanoparticles and the lubricant-rich tribolayer controlled wear in the hybrid composites. The intensity of abrasive, oxidation and delamination wear mechanisms decide the wear rate at any particular wear testing condition.