Wear Of Grits Research Articles

A novel method for exploring the wear resistance characteristics of ethylene propylene diene monomers‐polyamide elastomers with nano‐graphite

AbstractHansen solubility parameter theory and rheological laws were employed to investigate the microscopic cross‐linked network structure of the wear‐resistant elastomer based on ethylene propylene diene monomers (EPDM)‐polyamide elastomers (PAE)/graphite. With the condition of the same carbon black content, the wear volume of EPDM‐PAE increased after added wax powder and decreased by adding five percent graphite. The role of microscopic cross‐linked network on the wear‐resistant properties was specifically characterized by a highly linear synergistic relationship between wear volume and cross‐link density. The motion ability of micro chain segments has been characterized by the frequency sweep and the influence of the filler network has been represented by the strain sweep. Scanning electron microscope was used to characterize the micro filling structure, while stereomicroscope view was used to explore the wear interface. It was noteworthy that the graphite network layer formed on the abrasive surface on top of the abrasive grit wear transformed the wear mechanism into composite wear. This work was an innovative perspective to study rubber‐plastic/solid lubricant‐based wear‐resistant elastomers, based on microscopic network structures, which could help to obtain new wear‐resistant elastomers with specific properties.

Effect of single-grit wear on surface integrity of hardened stainless steel in dry grinding

Understanding grit wear and the consequent material removal mechanisms is of critical importance to elevating the performance of dry grinding. This study conducts a single-grit grinding analysis on the grit wear-induced thermomechanical variations and resultant surface integrity for ceramic alumina and CBN grits. The results reveal that the specific grinding force is lower when using the sharp ceramic alumina grit than that with the CBN grit, whereas an opposite result is presented as the grit wear is developed. The study demonstrates the possibility of dry grinding in terms of the wear mechanism, grit morphology, and temperature rise in the single-grit grinding.

Research on Failure Mechanism of Abrasive Belt and Effect on Sanding of Medium-Density Fiberboard (MDF)

Sanding is a very important process in MDF production. In this study, abrasive belts (P60 and P120) and MDF were used to conduct sanding experiments, and mass variation, surface morphology, and surface roughness of the abrasive belts were measured to analyze the failure process of the utilized abrasive belts. It is found that the mass of the abrasive belt mainly increased in the sanding process. The increase range of P60 is mainly within the scope of 0~0.02 g, while for P120, the mass change mostly fluctuates within 0~0.01 g. The surface roughness (Sa and Sku) of abrasive belts presents a down-and-up trend as sanding times increase, and Sa and Sku of P60 are both larger than those of P120. Wood fibers with adhesive blocked the space among grits and led to a “grits gathering” phenomenon. When the area of “grits gathering” is larger, it forms an abrasive belt “blocking”. Grit wear (dropping-off, fracture) and “blocking” constitute the two predominant patterns of the failure mechanism. This study is helpful to further improve wood-material-sanding theories, provide insights to investigate wear forms of other abrasive belts, and determine and extend the life of abrasive belts.

Grinding characteristics of CVD diamond grits in single grit grinding of SiC ceramics

Single crystalline diamond (SCD) grits are usually made by a high-pressure and high-temperature (HPHT) method and exhibit cuboctahedral shapes and smooth surfaces. In this paper, we synthesized new kinds of SCD grits and nanocrystalline diamond (NCD) grits by a chemical vapor deposition (CVD) method and explored their grinding performance by single grit grinding of SiC ceramics. Grinding by HPHT grits was also conducted for comparison. The CVD-SCD grits exhibit cuboctahedral shapes, but surfaces are covered by protruded twin crystals of several microns, while the NCD grits are spherical agglomerations of nano-grains. We demonstrated that these morphological features have profound influences on material removal behavior. Results show that the wear of NCD grits is dominated by wear flat and intergranular cracks. The worn NCD grits can exert intense rubbing and ploughing effects on the workpiece. In contrast, the wear of CVD-SCD grits is dominated by fracture of the protruded twin crystals. It is proved that the twins on the grit surface are effective cutting edges to remove the material in a micro scale and thus lead to the formation of fine grinding striations and smaller cracking pits, but this process has little influence on specific grinding energy. Besides, grits with rough twins, especially on the flank face, tend to exhibit lower grinding force ratios and thus better sharpness. Moreover, for grits with smooth rake faces, there exists an explicit critical undeformed chip thickness value around 0.4–0.6 μm, above which the material removal mechanism changes from ductile to brittle rapidly. However, for grits with rough twins on rake faces, this transition process becomes vague.

The wear mechanisms of diamond grits in grinding of alumina and yttria-stabilized zirconia under different cooling-lubrication schemes

Abrasion is the primary wear mechanism of diamond grits during grinding of advanced ceramics. This work not only highlights some unreported modes of wear of diamond grits but also illustrates and describes their mechanisms while grinding two dissimilar advanced ceramics, viz. alumina and yttria-stabilized zirconia (YSZ). Long-cycle plunge grinding of the ceramics was conducted with single-layer electroplated diamond wheels at 30 m/s and 50 m/s grinding speeds under three different cooling-lubrication schemes – flood cooling (FC), MQL-soluble oil (MQL-SO) and MQL-neat oil (MQL-NO). Radial wheel wear was measured employing indirect profilometry. Diamond grits on the electroplated wheels were observed under SEM before and after grinding to identify and characterize various modes of wear. Severe wheel loading was observed while grinding alumina and YSZ under FC and MQL-SO. Indentation fatigue fracture was found to be the dominant mode of diamond grit wear during alumina grinding under wheel loading conditions. The wear of diamond grits during YSZ grinding was dominated by thermal fatigue fracture at a higher grinding speed of 50 m/s. Thermal degradation of diamond grits was examined with Raman spectroscopy which revealed graphitization of some of the active diamond grits after YSZ grinding under FC and MQL-NO at 50 m/s.

Evolution of chemo-mechanical effects during single grit diamond scratching of monocrystalline silicon in the presence of potassium hydroxide

Efficiency and workability of silicon wafers for various applications depend on theirs surface integrity and damage free structures. Productivity of mechanical processing on silicon wafers is always limited by occurrence of cracks and brittle mode material removal at high depth of cut. This study presents a method of using controlled concentration of KOH solution during diamond micro-scratching of silicon and investigates the chemo-mechanical effects of KOH solution with respect to cutting speed. To establish the chemo-mechanical theory of cutting, responses of physical and material properties of silicon in presence of KOH solution are captured and correlated with mechanical responses during micro-scratching. Zeta potential and nanohardness are greatly reduced in KOH environment. Ductile mode is found to be extended by using 10 wt% KOH. Crack/chipping length is observed to be first increasing with increase in cutting speed at low range (0.6–20 mm/min) and then decreasing on further increase in the cutting speed (20–200 mm/min). Stability in cutting force signature and behavior of material flow along the scratch length is also found to be improved by using KOH. Adhesive wear and abrasive wear are found to be the main forms of single grit wear, which is significantly reduced in the presence of KOH. The experimental results on different mechanical and physical phenomena in this study are of great importance for establishing the theoretical insight into material removal behavior and selection of machining parameters during micro-machining of silicon wafer.

Analysis of diamond wheel wear and surface integrity in laser-assisted grinding of RB-SiC ceramics

Laser-assisted grinding provides a promising solution for achieving cost-efficient machining of hard and brittle materials. However, the heat generated by laser may cause the wear of diamond grinding wheel, including the wear of both diamond grits and bond material. Consequently, wheel wear has a knock-on effect on the ground surface roughness. Moreover, the laser irritation may also induce damage in the machined surface. This paper focuses on the investigation of wear of diamond grinding wheel and surface integrity in laser-assisted grinding of RB-SiC ceramics. Different temperatures were obtained by setting the laser power to explore the influence of heat on wheel wear and surface integrity. The wear modes and mechanism of the diamond grits and bond material were analyzed by combination of SEM detection and energy dispersion spectrum analysis. The results revealed that adhesion and pullout of diamond grits in laser-assisted grinding were the remarkable difference from those in conventional grinding due to the thermal softening of both RB-SiC specimen and bond material of the grinding wheel. Surface roughness was then improved owing to the increase in active grits. The Raman spectra of the machined surface also revealed different stress conditions and microstructures of the Si and SiC Phase in RB-SiC ceramics. These results provided insight on quality control in laser-assisted machining of RB-SiC ceramics.

Experimental and modeling characterization of wear and life expectancy of electroplated CBN grinding wheels

Abstract Wear and life expectancy of a nickel-electroplated monolayer of cubic boron nitride grinding wheels are characterized based on the wheel surface topological evolution, observed after grinding Inconel 718 super-alloys. The wheel is for surface or cylindrical grinding, and having 250 mm diameter, 10 mm thickness and B40/50 coarse grit size. A unique grit-workpiece interaction process, leading to a non-uniform spatial distribution of the grit wear has been identified. Largest grits have been observed to pullout rapidly, resulting in load redistribution to their surroundings, and leading to the attritious and fracture wear phase. The detailed analysis showed that the stresses on the cutting grits arising from the thermal shock are 3–5 folds those arising from mechanical cutting forces, and reach an order of magnitude differences for the high efficiency deep grinding (HEDG) process. It is also found that the grit wear rate is primarily dependent on the workpiece feed rate rather than the grinding wheel speed. The total wheel life is then constructed as the sum of pullout life (Phase-I) and attritious and fracture wear life (Phase-II). Model predictions for the total wheel life compare well to the experimental observations. This facilitates comparisons of different types of grinding configurations and design space exploration. As an example, the HEDG process is compared to a regular high speed grinding, and it is observed that HEDG configuration can deliver much higher material removal for the same amount of wheel wear.

Experimental and numerical analysis of thermal phenomena in the wear of single point diamond dressing tools

Grinding technologies represent a critical step in the production of high added-value and high precision parts for strategic industrial sectors such as aerospace, automotive, biomedical, and wind generation. Whilst a number of factors related to the grinding wheel are important for optimizing the grinding process, there is no doubt that the wheel surface topography is the most influential factor. Surface topography is induced not only by the nature of the wheel itself, but also, more importantly, by the dressing process. Dressing is periodically carried out in order to recover the abrasive capacity of the wheel once excessive wear of abrasive grits has occurred. The high temperatures and contact forces present in dressing lead to wear of the diamond dressing tool, which in turn damages the topography of the wheel surface. Although the scientific literature has paid attention to the phenomena involved in dressing tool wear, some issues are still in need of explanation. Thus, the aim of the present study was to address the unresolved issue concerning the relationship between dressing temperatures and dressing tool wear. Using a combined empirical and modeling approach, the work reported here shows that temperatures on the surface of the dressing tool can be reduced by as much as 35% when using high conductivity materials in the tool holder. In addition, a methodology has been devised in order to estimate accurate values of the heat partition ratio towards the diamond dressing tool. The results show that the heat partition depends primarily on the dressing mechanism involved. Its values range from 0.97 (when friction between the dressing tool and the grinding wheel prevails) to 0.54 when grain breakage and pull-out occur at higher dressing depths. It has been analyzed and measured the wear suffered by the diamond under interesting designed tests. It has been demonstrated that the effective reduction of temperatures during process led us to take a lower wear rate of the diamond.

Impact of material microstructure and diamond grit wear on surface finish in micro-grinding of RB-SiC/Si and WC/Co carbides

Ultra-precision surface grinding experiments were conducted at two different grinding conditions (rough and fine) to study the surface finish of RB-SiC/Si and WC/Co carbides, with Si and Co as binders, respectively. It was found that RB-SiC/Si and WC/Co showed two different types of surface generation mechanism under the same selected grinding conditions: brittle fractured surface of RB-SiC/Si and plastic deformation surface of WC/Co. Obvious micro-breaks occurred on SiC surface with a coarse grit wheel at higher material removal rate, but it changed to micro-pits at the phase boundary with a fine grit wheel at a lower material removal rate. Nevertheless, the surface characteristic only changed from rough grinding traces to finer for WC/Co. It was found that the surface finish of RB-SiC/Si and WC/Co was closely related to the material brittleness. The surface roughness (Ra) of RB-SiC/Si was limited to be about 20nm under both rough and fine grinding conditions while about 5nm (Ra) could be achieved for WC/Co under the fine condition. It was also identified that the surface profile of workpieces was replicated from diamond grits. To explain the difference in wavy surface profile at nanoscale, a simple model was built to illustrate the impact of grit wear.

A comparison on core drilling of silicon carbide and alumina engineering ceramics with mono-layer brazed diamond tool using surfactant as coolant

Core drilling with diamond tool is an efficient method for machining of holes in engineering ceramics. A comparative study on core drilling of silicon carbide and alumina engineering ceramics with mono-layer brazed diamond tool was carried out. Two surfactant (anionic type 1631 and nonionic type OP10) water solutions were used as coolant in core drilling. The effect of the coolant׳s type and concentration on drilling torque and drilling efficiency were also investigated. The morphologies of machined surface of ceramics and the wear of diamond grits were examined. According to the results, the anionic surfactant 1631 water solution produces a lower drilling torque and higher drilling efficiency than that of nonionic OP10. Both silicon carbide and alumina demonstrate a ductile regime of material removal under the lower maximum undeformed chip thickness (0.08mm). The wear of brazed diamond grits for drilling of silicon carbide is much severer than that of alumina.

Precision grinding of BK7 glasses using conditioned coarse-grained diamond wheel

For precision machining of large-sized optical elements, more attention is being paid to the ground surface quality, the processing costs and the machining efficiency. Besides the commonly used fine-grained diamond wheels, the coarse-grained diamond wheel is now also expected to be a promising tool with lower wheel wear rate and higher efficiency. However, conditioning of this kind of wheel is always a difficult issue to deal with. In this article, the efficient conditioning of the electroplated diamond wheel and precision grinding of BK7 glasses were investigated. Through the single diamond grit wear simulation, D3 steel was chosen as the conditioning tool. The worn diamond abrasive morphology and Raman spectroscopy analysis revealed the conditioning mechanism. Under different conditioning stages, the BK7 glasses were correspondingly ground exhibiting different surface integrity and grinding forces. The experimental results indicated that the wheel’s run-out error could be rapidly reduced to 5.8 µm because of the blend graphitization, passivation, diffusion and microcrushing of the diamond abrasives. The precision ground BK7 glasses could achieve a surface roughness of Ra < 20 nm and a subsurface crack depth around 2 µm, illustrating that the electroplated coarse-grained diamond wheel could be an alternative for precision grinding large-sized optical elements in terms of high accuracy, cost-effectiveness and high efficiency.

Exploring Grindability of Titanium Grade 1 Using Silicon Carbide Wheel

Titanium and its alloys are being increasingly used in aerospace engineering, corrosive fluid pumps, heat exchangers, sea vehicles, etc. However, it is quite difficult to grind for its high chemical reactivity, high strength, high hardenability and low thermal conductivity causing high grinding temperature, wheel loading, wheel material removal, grit wear, etc. Therefore, selection of wheel, wheel speed and fluid for grinding of titanium is important to achieve desirable surface quality. Formation of a stiff air layer is a major constrain restricting the fluid enter the grinding zone. Optimization of a method of grinding fluid application is essential to control thermal problems from interaction of the wheel grains with the work surface. Adopting an appropriate fluid delivery system may enhance grindability of titanium alloy and can reduce environmental pollution. In the present experimental work, surface roughness, grinding forces and grinding chips are observed under the condition of dry, and wet using a compound nozzle. Surface grinding of titanium Grade 1 alloy is done with the use of silicon carbide wheel. It is found out that grinding under wet with compound nozzle fluid delivery system exhibits fairly good grindability.

Performance of Laser Brazing Diamond Grinding Wheel in Face Grinding

A new technology kind of brazed monolayer cup diamond grinding wheel was developed via laser in an argon atmosphere. Grinding performances of this kind of brazed wheel in the surface grinding of the granites were studied. The experiment results show that the normal grinding forces and wear of diamond grits become higher with the increasing of the accumulated removal volume during grinding granites process. When continuous dry grinding was employed, the grits of the brazed diamond grinding wheel fail mainly in attired wear mode other than pull-out ones in conventional electroplated and sintered diamond tools, which indicates that the strong retention of brazing alloy to the diamond grits and longer service life of this kind of wheel.

On the grindability of low-carbon steel under dry, cryogenic and neat oil environments with monolayer brazed cBN and alumina wheels

Grinding of low-carbon steel often exhibits severe wheel loading due to the formation of long chips and high adhering tendency of the work material with the grits. Conventional composite-type alumina wheels are commercially utilised for grinding low-carbon steel. However, the actual nature of grit wear cannot be truly understood in a composite wheel. The truing and dressing conditions also have some influences on the wear mechanism. Therefore, in order to explore the wear pattern on a single layer of grits, monolayer brazed cBN, white and grey Al2O3 wheels were used in the present study. The grindability of AISI 1020 steel was evaluated under dry, liquid nitrogen and neat oil environments. The surface profile of the workpiece after being ground in each environmental condition was traced with a surface profilometer to reveal the mechanism of grit wear. The post-grinding conditions of the wheels were observed using scanning electron microscopy. The cBN wheel was found to outperform the alumina wheels in terms of grinding forces and grit wear. The wear of the cBN wheel was remarkably arrested with the application of neat oil. On the other hand, large-scale adhesion and breakage of grits in white alumina wheel were observed under cryogenic environment. In fact, the beneficial role of liquid nitrogen could not be realised in reducing grinding forces and grit wear with all the three types of wheel. A lubricating agent like neat oil appeared to be more suitable than cryogenic cooling when grinding low-carbon steel.

Micro/nano Indentation and Single Grit Diamond Grinding Mechanism on Ultra Pure Fused Silica

The existing research about ductile grinding of fused silica glass was mainly focused on how to carry out ductile regime material removal for generating very "smoothed" surface and investigate the machining-induced damage in the grinding in order to reduce or eliminate the subsurface damage.The brittle/ductile transition behavior of optical glass materials and the wear of diamond wheel are the most important factors for ductile grinding of optical glass.In this paper,the critical brittle/ductile depth,the influence factors on brittle/ductile transition behavior,the wear of diamond grits in diamond grinding of ultra pure fused silica(UPFS) are investigated by means of micro/nano indentation technique,as well as single grit diamond grinding on an ultra-stiff machine tool,Tetraform "C".The single grit grinding processes are in-process monitored using acoustic emission(AE) and force dynamometer simultaneously.The wear of diamond grits,morphology and subsurface integrity of the machined groves are examined with atomic force microscope(AFM) and scanning electron microscope(SEM).The critical brittle/ductile depth of more than 0.5 μm is achieved.When compared to the using roof-like grits,by using pyramidal diamonds leads to higher critical depths of scratch with identical grinding parameters.However,the influence of grit shapes on the critical depth is not significant as supposed.The grinding force increased linearly with depth of cut in the ductile removal regime,but in brittle removal regime,there are large fluctuations instead of forces increase.The SEM photographs of the cross-section profile show that the median cracks dominate the crack patterns beneath the single grooves.Furthermore,The SEM photographs show multi worn patterns of diamond grits,indicating an inhomogeneous wear mechanism of diamond grits in grinding of fused silica with diamond grinding wheels.The proposed research provides the basal technical theory for improving the ultra-precision grinding of UPFS.

Temperatures and wear mechanisms in dressing of vitrified bonded grinding wheels

For the first time dressing temperatures were measured directly in the contact zone of grinding and diamond dressing tool. With average temperatures of 400 °C and maximum temperatures of 810 °C without cooling lubricant, the need to cool the dressing tool sufficiently is affirmed. For a diamond dressing tile and form rollers in contact with vitrified bonded corundum and CBN wheels, the main grit wear mechanisms were adhesions instead of breakage or high volumetric splintering. Extensive analyses proved that components of the grinding wheel bonding and abrasives were molten during the dressing process and solidified amorphously. This verifies high peak surface pressures and flash temperatures.

Wear of Brazed Diamond Wheel in Grinding of Cemented Carbide

Grinding forces, protrusion height, grinding temperatures and wear of diamond grits have been studied in grinding cemented carbide YG8 with a single-layer vacuum brazed diamond wheel. The experiment results indicate that the primary wear progression of diamond grits in the whole grinding process follows the mode of whole diamonds, flat diamonds when grinding of the cemented carbide. The worn mechanism of the failure of diamond grits was discussed and possible solutions are recommended. The proportions of diamond conditions and the mean protrusion height of grains are more closely related to grinding forces and grinding temperatures. The grinding forces, force ratio and grinding temperatures decreased with the increasing proportions of whole crystal and the decreasing mean protrusion height of diamond grits, and the tangential and normal force components increased with the gradual wear of the brazed diamond wheel during a long-time grinding process. It shows great potential in improving thermal damage of cemented carbides by reduces grinding temperature with vacuum brazing diamond wheels.

Abrasiveness properties assessment of coated abrasives for precision belt grinding

This paper addresses a study to achieve a method of assessment of coated abrasives for precision belt grinding based on the identification of the prevailing relationships between the changing features of fixed grains on flexible coated belts and grinding performance. A set of parameters was defined which describe the aluminium oxide resin-bonded belt characteristics including active grits density, cutting edge dullness, chip storage space and mean effective indentation. A parametric study was made of the effects of coated belt characteristics on surface finish performance with different grain sizes for grinding different workpiece materials. Experimental results are discussed in relation to the prevailing mechanisms of the process at the belt-work interface which can be separated into cutting and ploughing components. This enables also to describe the grit wear mechanisms operating with coated abrasives when grinding two engineering materials.

Abrasive wear of individual grits in diamond rollers and sticks and its relation to the overall tool wear in dressing operations

Abrasive wear of individual grits in diamond dressing tools during the dressing of abrasive wheels is studied. The wear rate is assessed analytically allowing for mechanical-statistical and temperature characteristics of the grit operation in dressing with rollers and sticks, as well as for the temperature-induced variations of the diamond hardness. A relationship is established between wear of individual grits and that of the diamond-containing layer as a whole.