Two-Body Abrasive Wear of the Outside Shell Surfaces of Mollusc <Emphasis Type="Italic">Lamprotula fibrosa</Emphasis> Heude, <Emphasis Type="Italic">Rapana venosa</Emphasis> Valenciennes and <Emphasis Type="Italic">Dosinia anus</Emphasis> Philippi

Natural biological surfaces and biomaterials have some distinguishing properties for adapting themselves to natural surroundings. The outside shell surfaces of mollusc species often undergo the abrasive wear action from the sand particles in water sand slurry in natural conditions. The two-body abrasive wear behavior of the outside shell surfaces of three mollusc species Lamprotula fibrosa Heude, Rapana venosa Valenciennes and Dosinia anus Philippi was examined. Abrasive material used for tests were quartz sand (96.5 wt.%) with three different size ranges and powdered bentonite (3.5 wt.%). The two-body abrasive wear tests were run on a rotary disc type abrasive wear testing machine. The results showed that the abrasion resistance of the outside shell surfaces of the three mollusc species was higher when the corrugations on the shell surfaces were perpendicular to the sliding direction of the abrasive material than that when the corrugations on the shell surfaces were parallel to the sliding direction of the abrasive material. Basically, the shell of Lamprotula fibrosa Heude possessed the highest abrasion resistance among the three species of shell; the abrasion resistance of the shell of Rapana venosa Valenciennes was the lowest; and the abraded depth of the three species of shell increased with an increased abrasive particle size and relative sliding velocity. The abraded surfaces were observed with scanning electron microscope.     

A study of abrasive wear mechanisms in cobalt-base alloys

Single-point scratch tests were used to investigate material removal mechanisms in two cobalt-base powder metallurgy alloys 6 and 19. Each alloy was produced with fine, medium and coarse chromium-rich M₇C₃ carbides in a cobalt-rich f.c.c. matrix phase. In a separate study, the low stress abrasion resistance was found to increase with carbide size. The present scratch test study was designed to simulate low stress abrasion conditions by using single quartz abrasive particles as scratch tools, and the results are compared with those from scratches made using regularly shaped diamond tools.Single- and multiple-pass scratches were made with several different loads using Vickers diamond pyramids and single quartz abrasive particles on metallographically prepared surfaces. Single-pass scratches were also made on preworn surfaces by using a Vickers diamond.Single-pass diamond scratches exhibited ploughing and extensive coarse slip bands in the matrix phase of metallographic specimens. Evidence of carbide deformation and of slip band cracking of the matrix material was observed also. Coarse slip bands were not observed on preworn surfaces. On both polished and preworn surfaces, thin layers of the matrix phase were often smeared over the carbides, and coarse carbides were extensively cracked. Multiple-pass diamond scratches on metallographic specimens exhibited thin detached layers of matrix material in the scratch groove and tongue-like extruded lips of material stretching away from the ridge. Particles of similar size and shape were found on the diamond pyramid.Scratch tests with quartz particles exhibited slip band cracking, smeared matrix material over the carbides and cracking and pulling out of carbides similar to observations with diamond tools. However, extensive ploughing and shear lip formation were not observed in quartz scratches, and wear debris particles in the scratch and on the tool were rounded and very much smaller than those produced by multiple-pass diamond scratches. Wear debris in multiple-pass quartz scratches were observed to pile up at the leading edges of the carbides, which protruded from the surface because of preferential wear of the matrix phase, as observed in low stress quartz abrasion.With both quartz and diamond tools, the material with the finest carbides (alloy 19A) exhibited large pits where cracks had traveled along the carbide-matrix interface and between carbides. Very little evidence of pulling out of carbides in the fine carbide materials was found.     

Effects of grit size on abrasion with coated abrasives

This paper is concerned with identifying the causes of grit size effects in the initial performance of fresh coated abrasives and the deterioration of coated abrasive performance with continued use. Abrasion tests were performed on an instrumented pin-on-cylinder apparatus which had removable segments for observing the coated abrasive surface in the scanning electron microscope (SEM). This allowed for a direct correlation between measurements of coated abrasive performance and SEM observations of coated abrasive morphology. With coated abrasives containing finer grit sizes, numerous adhesive wear particles were found on the coated abrasive surface; this supports the theory that the smaller initial abrasion rate with finer grits is due to abrasive grains making “elastic” contact with the metal specimen at loads insufficient for cutting. With continued use, the rapid deterioration in performance with finer grits was accompanied by a buildup of metal caused by capping of the abrasive grain tips with metal chips and by clogging due to metal chips and adhesive wear particles becoming stuck between the grains. With coarser grits, which were found to experience extensive grain fracture followed by some grain capping and flattening but virtually no clogging, the deterioration in coated abrasive performance was very much less.     

Effect of carbide size on the abrasion of cobalt-base powder metallurgy alloys

A study of the effect of carbide size on the abrasion resistance of two cobalt-base powder metallurgy alloys, alloys 6 and 19, was conducted using low stress abrasion with a relatively hard abrasive, A1₂O₃. Specimens of each alloy were produced with different carbide sizes but with a constant carbide volume fraction. The wear test results show a monotonie decrease in wear rate with increasing carbide size.Scanning electron microscopy of the worn surfaces and of wear debris particles shows that the primary material removal mechanism is micromachining. Small carbides provide little resistance to micromachining because of the fact that many of them are contained entirely in the volume of micromachining chips. The large carbides must be directly cut by the abrasive particles. Other less frequently observed material removal mechanisms included direct carbide pull-out and the formation of large pits in fine carbide specimens. These processes are considered secondary in the present work, but they may have greater importance in wear by relatively soft abrasives which do not cut chips from the carbide phase of these alloys. Some indication of this is provided by limited studies using a relatively soft abrasive, rounded quartz.     

The effects of welding processes on abrasive wear resistance for hardfacing deposits

In this research, four kinds of welding deposits were evaluated, applied through two different welding processes: flux cored arc welding (FCAW) and shielded metal arc welding (SMAW). The other variable of the tests was the deposited layers. The hardfacing deposits were evaluated using the dry sand-rubber wheel machine according to procedure A of the ASTM G65 standard. Optical and scanning electron microscopy was used for the characterization of the microstructure and worn surface of deposits. FCAW welds presented higher abrasive wear resistance than the SMAW deposits. The hardfacing deposit formed by uniformly distributed carbides rich in titanium presented the highest abrasive wear resistance. Abrasive wear resistance was higher when three layers were applied, except for SMAW-D deposit. It was not possible to get a clear relation between hardness and the abrasive wear resistance of the deposits. The results showed that the most important variable to improve abrasion resistance is the microstructure of hardfacing deposits, where the carbides act as barriers to abrasive particle cutting.     

Solid particle erosion behaviour of hardfacing deposits on cast iron—Influence of deposit microstructure and erodent particles

Solid particle erosion (SPE) behaviour of different hardfacing electrodes deposited on gray cast iron (ASTM 2500) was studied using quartz sand and iron ore as erodent particles. Erosion test was carried out as per ASTM G76 test method. Considerable differences in erosion rates were found among different hardfacing electrodes at normal impact. Both volume fraction of carbides and type of carbides played an important role in the erosion behaviour of the deposits when quartz sand was used as erodent particles. On the other hand, only volume fraction of carbides irrespective of carbide type mainly controlled the erosion rate of the same deposits when iron ore was used as erodent particles. Such difference is attributed due to difference in metal removal mechanisms by the two erodent particles used. Hard quartz sand particles were capable of causing damage to most of the carbides while relatively softer iron ore particles were unable to fracture any carbides present in the microstructures. Furthermore, relatively brittle matrix led to high erosion rate which is significant in case of quartz sand as erodent, but not in case of iron ore particles. Like abrasion resistance, hardness is not a true index of erosion resistance of hardfacing deposits.     

A study of abrasive wear mechanisms using diamond and alumina scratch tests

Scratch tests using alumina (Al₂O₃) abrasive particles and Vickers diamond pyramids were employed to study material removal mechanisms in the abrasion of cobalt-base powder metallurgy alloys 6 and 19. The alloys were specially prepared to produce either fine or coarse carbides in order to study the effects of carbide size. Scanning electron microscopy was used to analyze the scratch grooves, the scratch tools and the wear debris particles.

Comparison of scratch tests with Al₂O₃ and diamond pyramids shows that many features produced by the extremely hard regularly shaped diamond tools are different from those produced by irregular Al₂O₃ particles. Except for differences produced by tool wear, multiple-pass Al₂O₃ scratch tests provide excellent reproduction of the material removal processes which occur in low stress Al₂O₃ abrasion. Al₂O₃ scratches produced both chip-like and fine irregular debris particles similar to those extracted from spent abrasive used in wear testing.

Material removal in the fine carbide alloys is facilitated by the direct removal of entire carbides within the volume of micromachining chips removed from the scratch groove. In coarse carbide alloys, machining chips from large carbides are observed, but the depth of cut in the carbide phase is less than that in the f.c.c. matrix and this leads to a decrease in the volume of material removed. Direct comparison of chips removed from fine and coarse carbide alloys by the same Al₂O₃ particle shows larger chips from the fine carbide material.

The effects of subsurface deformation and surface irregularities on material removal were studied by carrying out scratch tests on specimens subjected to prior abrasion and by investigating multiple-pass scratches in the same scratch groove.     

Study of solid particle erosion on AISI D2 using angular silicon carbide and steel round grit particles

Abstract

In this study, the performance of AISI D2 steel subjected to solid particle erosion tests was analysed. This material has applications for tools and dies for blanking, wood milling cutters, cold-extruding and other operations requiring high compressive strength and excellent wear resistance. The erosion tests performed by using a rig developed according to some parameters of the ASTM G76-95 standard. Two abrasive were used, angular silicon carbide (SiC) and steel round grit, both, with a particle size of 400–420 μm. This allowed comparing the erosion severity of each abrasive particle. The tests were conducted using four different incident angles 30, 45, 60 and 90° with a particle velocity of 24±2 m s^?1 and a flow rate of 21±2·5 g min^?1 for silicon carbide and 48·5±3·5 g min^?1 for the steel round grit. The exposure testing time was 10 min. Subsequently, the surface damage was analysed with a scanning electron microscope (SEM) to identify the wear mechanisms. Additionally, atomic force microscopy (AFM) was conducted in order to obtain roughness of the surface damage at 60°. The results indicated that higher amount of mass loss was obtained by angular silicon carbide particles.     

Some remarks on particle size effects on the abrasion of a range of Fe based alloys

The low-stress three body abrasion behaviour of a range of steels was investigated. The tests were carried out in a rubber wheel tester (according to ASTM G65-94, reapproved in 2000) at room temperature. The abrasive particles used were angular alumina particles of four different sizes. The results showed that, in general, the smaller particles (50 and 125 μm average size) caused more damage. With these particles, observations of surface morphology indicated a more intense cutting and ploughing action, leading to more damage, whereas bigger particles i.e. larger 250 and 560 μm particles produced less damage, and their action involved more plastic deformation type wear. The 304 SS had a lower abrasion resistance than the 310 SS. For the austentic and ferritic steels the subsurface deformation was larger for impact with the coarser particles. Variations in substrate hardness had no effect on the abrasive behaviour observed. On the whole, the hardest steel (mild steel in martensitic condition) showed the higher extent of damage, irrespective of particle size.     

Ball-cratering abrasion tests of high-Cr white cast irons

The application of a ball-cratering method to test three-body abrasive wear of bulk materials in the presence of large abrasive particles has been investigated. Three high-Cr white cast irons (WCIs) with different material properties were used as wear samples. Abrasive slurries contained two types of abrasive particles, silica sand and crushed quartz. Silica sand and crushed quartz particles have similar chemical composition and hardness but differ in sharpness. Wear rates of WCI samples were determined and the worn surfaces were examined by optical microscopy, SEM and Talysurf profilometry.It was found that the ball-cratering test can differentiate between the wear resistances of materials with similar properties. The wear resistance of WCIs in the presence of silica sand increased with increasing the hardness of the wear sample and decreasing the size of carbides in the microstructure. Smaller silica sand particles caused less wear damage than larger silica sand particles, even though the smaller particles were slightly sharper than the larger ones. When silica sand and quartz particles of the same size were used, the angular quartz particles caused much higher wear than the rounded silica sand particles. Surface morphologies of the wear craters on the WCI samples were examined in an SEM and then compared with the morphologies of the worn surfaces from slurry pumps. It was found that the silica sand particles generated surface morphologies similar to those found in the worn slurry pumps. In these surfaces the matrix was preferentially worn out and hard carbides were protruding. Wear surface morphologies produced by the angular quartz particles were different. They consisted of numerous superimposed indents and the microstructure phases were not distinguishable. This indicates that the type of abrasive particles used in ball-cratering testing significantly affects the test outcomes in terms of wear rates and wear surface morphology.     

A tribotesting method for evaluating cemented carbide tribo-performance

The abrasive wear properties of materials in sliding contact with solid mineral particles during the comminution process have been studied. The equipment used can simulate the tribo-conditions inside coal pulverisers. Using this experimental apparatus, a number of different cemented tungsten carbides have been tested and classified according to their resistance to abrasive wear in rubbing contact with particulate coal. The paper shows that the wear results can be used to estimate the resistance of a material to brittle fragmentation and chipping of the edges during tribo-contact with solid particles. An equation is presented which enables calculation of the fracture resistance factor, K_WR, based on results from carefully controlled repeated abrasion tests.     

Abrasive wear characteristics of a zinc-based alloy and zinc-alloy/SiC composite

An attempt has been made in this investigation to assess the contribution of various parameters towards governing the abrasive wear response of a zinc-based alloy under the conditions of varying applied loads and sliding distances. The factors whose contribution has been examined include deterioration in the cutting efficiency of the abrasive medium, role played by the SiC particles (dispersed in the alloy matrix) in terms of their degradation and resistance offered by them against the destructive action of the abrasive, subsurface hardening of the matrix and such other related aspects. Four types of abrasion tests were conducted on the samples to achieve the goal. The (abrasion) tests involved the use of (i) fresh as well as preworn surfaces of the samples and (ii) fresh and degraded abrasive media in four different combinations.The study suggests that the mentioned factors contribute to a varying degree towards controlling the (high-stress) abrasive wear behaviour of the specimens. However, degradation in the cutting efficiency of the abrasive medium (through capping, clogging, attrition and shelling) dominates over the influence of other parameters such as abrasion induced subsurface hardening of the matrix. Reinforcement of the SiC particles in the alloy matrix offered improved wear resistance (inverse of wear rate) under less severe conditions such as at low applied loads, wherein the dispersoid (SiC) particles could be retained by the matrix due to low cutting depths made by the abrasive particles. The dispersoid particles deteriorated the wear response of the matrix under more severe conditions of abrasion, such as at high loads, because of larger cutting depths causing fracturing and partial removal of the reinforcement (SiC) particles. The observed wear response of the samples has further been substantiated through the characteristics of wear surfaces, debris particles and abrasive medium after testing the matrix alloy and composite in a typical test condition expected to affect the abrasive medium and test specimens to the largest extent.     

Abrasive wear of high speed steels: Influence of abrasive particles and primary carbides on wear resistance

A ball cratering test has been used to investigate the abrasive wear of high speed steels with different volume fraction and size of primary carbides. Three different abrasives, SiC, Al₂O₃ and ZrO₂ were used. Wear mechanisms were investigated by scanning electron microscopy (SEM). A good correlation between the hardness of the abrasives and the abrasive wear coefficient was found. Higher abrasive wear resistance was determined for steels containing coarser primary carbides compared to those without or with smaller carbides. The most pronounced difference in abrasive wear resistance was found for Al₂O₃ abrasives. This indicates that in ball cratering the abrasive medium has to be chosen properly, i.e. with a hardness adjusted to those of both primary carbides and martensitic matrix, to obtain results suitable to rank high speed steels with respect to abrasion resistance.     

Abrasive wear resistance of some commercial abrasion resistant steels evaluated by laboratory test methods

The aim of the present study is to evaluate the abrasive wear resistance of some potential abrasion resistant steels exposed to different types of abrasive wear contact conditions typical of mining and transportation applications. The steels investigated, include a ferritic stainless steel, a medium alloyed ferritic carbon steel and a medium alloyed martensitic carbon steel.The abrasive wear resistance of the steels was evaluated using two different laboratory test methods, i.e. pin-on-disc testing and paddle wear testing that expose the materials to sliding abrasion and impact abrasion, respectively. All tests were performed under dry conditions in air at room temperature. In order to evaluate the tribological response of the different steels post-test characterization of the worn surfaces were performed using optical surface profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Besides, characterization of the wear induced sub-surface microstructure was performed using optical microscopy.The results show that depending on the abrasive conditions a combination of high hardness and toughness (fracture strain) is of importance in order to obtain a high wear resistance. In the pin-on-disc test (i.e. in sliding abrasion) these properties seem to be controlled by the as-rolled microstructure of the steels although a thin triboinduced sub-surface layer (5–10 μm in thickness) may influence the results. In contrast, in the paddle wear test (i.e. in impact abrasion), resulting in higher forces acting perpendicular to the surface by impacting stones, these properties are definitely controlled by the properties of the active sub-surface layer which also contains small imbedded stone fragments.     

Preparation mechanism and grinding performance of single-layer self-lubrication brazed CBN abrasive wheels

In order to fabricate single-layer self-lubrication brazed cubic boron nitride (CBN) abrasive wheels, brazing experiments of graphite particles and AISI 1045 steel were carried out using Ag–Cu–Ti filler alloy. Optical microscope, scanning electron microscope, energy-dispersive spectroscopy, and X-ray diffraction were employed to characterize the microstructure and phase constitution of the brazing interface between graphite particles and Ag–Cu–Ti alloy. The formation mechanism was discussed. The results show that TiC resultants are formed via the diffusion behavior of Ti atoms and C atoms towards the joining interface. The chemical resultants of TiC have the granular shape at the early stage. Then, they grow across the joining interface between the graphite particle and Ag–Cu–Ti alloy. Finally, the continuous lamellar TiC compounds come into being around the graphite particle. Chemical joining of graphite particles and Ag–Cu–Ti filler alloy is accordingly realized. A comparative experiment displayed that the single-layer self-lubrication brazed CBN abrasive wheel has better performance than the conventional brazed counterpart.     

Tribological Behavior of a 0.33% C Dual-Phase Steel with Pre I/C Hardening and Tempering Treatment under Abrasive Wear Condition

The present study investigates the effect of prior hardening and tempering treatment on the microstructure, mechanical properties, and high-stress abrasive wear response of 0.33% carbon dual-phase (DP) steel. For this purpose, two different DP steels were produced by subjecting the as-received steel to hardening (DP-H) and hardening + tempering (DP-HT) treatments prior to the intercritical (I/C) annealing treatment. These steels along with the as-received steel were subsequently characterized by optical and scanning electron microscopy (SEM) metallography. Furthermore, tensile properties were evaluated along with microhardness measurements. The fracture surfaces of the failed tensile specimens were studied under SEM. Prior hardening and tempering treatment resulted in the formation of a nearly spherical martensite (aspect ratio = 1.2 ± 0.13) phase along with fine iron carbides in DP-HT steel. These fine iron carbides and spherical martensite act as the void nucleation sites in DP-HT steel. Therefore, DP-HT steel exhibits good ductility along with reasonable strength. On contrary, DP-H steel exhibits the presence of a fine elongated martensite (aspect ratio = 6.1 ± 3) phase, which causes poor ductility. Furthermore, abrasion tests were carried out at varying sliding distances at three different applied loads. Dual-phase treatment results in improved overall wear response. Moreover, tempering of prior hardened steel leads to improvement in wear resistance in DP-HT steel under all conditions studied in comparison with DP-H steel. This is attributed to higher strain hardening and greater resistance to particle scooping in DP-HT steel.     

Abrasive wear behaviour of B4C particle reinforced Al2024 MMCs

In this study, the effects of volume fraction and particle size of boron carbide on the abrasive wear properties of B₄C particle reinforced aluminium alloy composites have been studied. For this purpose, a block-on-disc abrasion test apparatus was utilized where the samples slid against the abrasive suspension mixture at room conditions. The volume loss, specific wear rate and roughness of the samples have been evaluated. The effects of sliding time, particle content and particle size of B₄C particles on the abrasive wear properties of the composites have been investigated. The dominant wear mechanisms were identified using scanning electron microscopy. The results showed that the specific wear rate of composites decreased with increasing particle volume fraction. Furthermore, the specific wear rate decreased with increasing the size of particle for the composites containing the same amount of B₄C. Hence, it is deduced that aluminium alloy composites reinforced with larger B₄C particles are more effective against the abrasive suspension mixture than those reinforced with smaller B₄C particles.     

Polishing of mica-filled epoxy

Polishing experiments on mica-filled epoxy by abrasive papers and lapping compounds showed that a significant smoothing of the surface only occurred when the particle size of the abrasive in the lapping compound was less than that of the mica particles. When the smoothing occurred some mica particles were chipped away while others were left standing proud of the epoxy surface. Stereo photomicrographs taken in a scanning electron microscope, surface profiles and statistical parameters for the profiles all confirmed the above conclusion.     

高压磨料水喷嘴磨损实验研究

本文采用硬质合金和陶瓷材料制成喷嘴．在高压水设备上进行了磨损实验研究。结果表明，影响其耐磨性主要因素是喷嘴材料、表面硬度及高压磨料水工艺参数。同时采扫描电镜对喷嘴磨损表面进行了分析。     

硬质颗粒复合合金的组织和耐磨性

本文强调基体合金组织对硬质颗粒复合合金耐磨性的决定作用,设计并通过“真空吸附铸件表面合金化工艺”,在灰铁铸件表层稳定地制得了以不同粒度的铸造碳化钨颗粒均匀分布于高合金铬钨白口铸铁中的复合合金。磨料磨损试验表明：基体合金组织对复合合金二体尤其是三体高应力磨损耐磨性有决定性的作用;以马氏体合金白口铁为基体合金的复合合金,在二体及三体磨损条件下均具有极高的耐磨性,铸造碳化钨颗粒愈粗,复合合金耐磨性愈高,当颗粒尺寸由140～200目增大到18～28目时,其在二体和三体磨损条件下的耐磨性分别是马氏体白口铁15Cr2Mo1Cu的9～31倍和2.8～6.7倍。