Silicon Carbide Abrasive Particles Research Articles

VITAL BLEACHING AND ENAMEL MICROABRASION FOLLOWED BY DIRECT COMPOSITE VENEERS FOR THE MANAGEMENT OF FLUOROSIS STAINS: A CASE REPORT

Fluorosis stains can signicantly impact the esthetic appearance of teeth. In this case report, we describe the management of uorosis stains in a 15-year-old male patient through a combination of vital bleaching, enamel microabrasion, and direct composite veneers. Vital bleaching using hydrogen peroxide was employed to decolorize the stains, followed by enamel microabrasion using Opalustre containing 6.6% HCl acid and silicon carbide abrasive particles to remove the remaining supercial bands. Direct composite veneers were done to the central incisors to further improve the esthetic outcome. This case demonstrates the efcacy of this treatment approach in the management of uorosis stains.

Study on the sintering mechanism and properties of porous ceramics prepared by silicon carbide abrasive particles with multi-mineral sintering additives and silica sols

Reducing the sintering temperature of SiC ceramics while maintaining performance has been a significant challenge. This study proposes the preparation of SiC porous ceramics at lower sintering temperatures using industrial-grade SiC abrasives, instead of expensive high purity SiC ceramic particles, as ceramic aggregates by combining two process routes, namely liquid-phase sintering and additive doping, with industrial silica sol as the liquid-phase binder and three common minerals, namely kaolin, talc, and bentonite, as sintering additives. SiC ceramic precast blanks were first prepared by a semi-solid injection moulding process. The reasonable SiC sintering temperature was determined to be 1400 °C by studying the effect of sintering temperature on the component composition and microscopic morphology of the blanks. Then, SiC porous ceramics with macroscopic and microscopic pore structures were successfully prepared using an organic foam impregnation-high temperature sintering process, in which the maximum compressive load was 210.2 N at a porosity of 72.66%. Finally, the rationality of this process route was determined, which shows that this technology can reduce the complexity and production cost with cheaper raw materials and lower sintering temperature without atmosphere protection.

Machining performance evaluation under recently developed sustainable HAJM process of zirconia ceramic using hot SiC abrasives: An experimental and simulation approach

The proposed research work accomplishes the experimental study and computational fluid dynamics (CFD) technique for erosive footprint prediction extent in hot abrasive jet machining (HAJMing) constraints on target surface erosion rate, surface roughness of intricately shaped tapered holes generation. The CFD-obtained footprints were in superior agreement with experimentally measured data. HAJMing process uses a relatively high speed air-hot abrasive stream to produce both high accuracy micro-channels and tapered holes. HAJM also defines itself phenomenal competence over all advanced manufacturing techniques due to its growing demands for better surface reliability with defects (mostly stress, heat) free surfaces. Zirconia is widely accepted and associated in the non-conventional machining processes and industries with the years of track on record of proven performance in a vast number of brittle materials. Most perceptible act in this research is the selection of abrasive particle to achieve the appropriate intricate shaped holes on zirconia ceramic with hot silicon carbide (SiC) abrasives. Machining of these features are done with varying the abrasive temperature. Optical microscopic view was considered for the generation of machined holes during HAJMing. All the experimental data were presented to study the effect of machining constraints on target surface erosion rate and surface roughness using HAJMing. Single impact experiments were executed to measure the target surface erosion due to impact of individual hot silicon carbide abrasive particles. An experimental setup has been designed to conduct the machining trials using Box-Behnken design of experiments. It is also shown that the generated workpiece surface contour and erosion rate are the function of machining constraints which have a negligible influence on air-abrasive flow characteristics. This research work also deals with the sustainability assessment under environmental-friendly hot abrasive-assisted machining conditions.

Experimental solid particle erosion of silicon nitride: Optical investigation

An experimental solid particle erosion study was conducted to investigate the erosion of silicon nitride at different angles of attack using optical techniques. During the erosion process, it has been noticed that when silicon carbide abrasive particles came into contact with the target material, a shower of sparks was created due to the high heat generated causing localized melting on the surface of the abrasive particles. Shadow Moiré, an inexpensive and easy-to-setup technique, was then used to estimate the depth, width, and circularity of the erosion scars. The same parameters were also measured using a non-contact optical profilometer to evaluate the accuracy of shadow moiré technique. A good agreement has been observed where the shadow moiré technique was capable of estimating the circularity, maximum depth, and the width to depth ratio of the erosion scars with a maximum error of 15%, 16%, and 12%, respectively.

Investigation on MRR and DOC of the micro-holes generated on quartz using silicon carbide by FB-HAJM

This proposed study represents the development of hot abrasive jet machine setup as well as to study the parametric optimization using silicon carbide abrasive and quartz workpiece. In this research work, micromachining has been done on Quartz material by newly developed fluidized bed hot abrasive jet machine using silicon carbide abrasive particles with various grit sizes by taking different input machining constraints i.e. pressure (P), Temperature (T) and Nozzle tip distance (NTD) for analyzing the outcome responses i.e. Displacement of cut (DOC) and Material removal rate (MRR). Fabrication and modification of heating cum abrasive-air mixing chamber, abrasive delivery system and pressurized feed system are done to investigate the influence of various effects of machining process parameters. Also Grey relational analysis (GRA) has been used to find out the finest parametric combination of input machining parameters.

Experimental study on surface roughness by using abrasive jet machine

Abstract A machining operation is basically termed a material removal process, where material is removed in the form of chips. In a machining operation, the output parameter is achieved by controlling various input parameters. Abrasive jet machining process is an unconventional machining process. In this process a high velocity of abrasive particles directed to hit on the work piece to remove the material. Abrasive jet machining process is especially useful to perform operations on brittle materials, ductile materials. This process is mainly used for producing intricate shapes and also perform deburring and cleaning operations. Abrasive materials like aluminum oxide, silicon carbide etc. In this paper measuring the surface roughness on ductile materials like mild steel and also studying how aluminum oxide, silicon carbide abrasive particles effected on work piece.

Nano-finishing Studies Using Elastically Dominant Polymers Blend Abrasive Flow Finishing Medium

Abrasive flow finishing (AFF) process is one of the advanced finishing processes that uses polymer rheological abrasive medium to finish simple to complex surface features. AFF process comprises of machine set-up, tooling and medium. Among these three AFF process components, medium plays an important role. Depending on medium constituents and its quantity, the rheological property as well as its finishing abilities varies. In the current research work, soft styrene polymer and silicone polymers are blended along with additives and silicon carbide abrasive particles to make medium. The viscous and elastic properties of base polymers blend are varied using softeners (stearate), plasticizers (hydrocarbon oils) and abrasive particles. Finishing experiments are conducted on Al alloy/SiC (10%) metal matrix composites using central composite rotatable design as well as the responses are modeled using response surface methodology. The best surface finish achieved with optimally blended abrasive medium on Al alloy/SiC (10%) metal matrix composite (MMC) is 110nm.

Study Regarding the Surface State of Composite Resins After Finishing and Polishing Using Different Systems

The aim of this study was to evaluate the influence of different finishing and polishing systems and of composite resins structure on surface state of the restoration. Cylindrical samples from two different composite resins (Filtek Z 550 and Filtek Z 250, 3M ESPE) were obtained. In group 1 the samples were not finished and polished. In groups 2-4 the samples were submitted to finishing procedure using two tungsten carbide burs, then polished using three different polishing systems: three steps diamond abrasive polishers (Kenda CGI, Lichtenstein) - group 2, one step silicon carbide abrasive particles brush (Occlubrush, KerrHawe SA, Switzerland) - group 3 and two steps Sof-Lex spiral wheels (3M ESPE) - group 4. Half of the samples in each group were subjected to surface microstructure evaluation using a scanning electron mycroscope. The other half of the samples was subjected to surface state assessment using profilometery. All the investigated finishing and polishing systems leaded to increased surface roughness when compared to the roughness of composite resins placed in direct contact to celluloid clear matrix. The surface roughness of both microfilled-hybrid and nanofilled-hybrid composite resins finished and polished with different systems were influenced mostly by the polishing system and less by the composite resin structure.

Modeling of surface roughness in the magnetorheological cylindrical finishing process

The magnetorheological cylindrical finishing process is developed for fine finishing of the internal surface of cylindrical objects. The process uses smart fluid known as magnetorheological polishing fluid. This fluid consists of carbonyl iron (CI) and silicon carbide (SiC) abrasive particles mixed in the base fluid. The magnetorheological cylindrical finishing process consists of an internal finishing tool, which induces magnetic field over its outer surface due to which CI particles experience magnetic force and form chains between the magnetized tool outer surface and inner surface of the cylindrical workpiece. The CI particles push SiC abrasive particles towards the inner surface of the cylindrical workpiece and with the movement of finishing tool inside the cylindrical workpiece, finishing is performed in the process. In the present work, a mathematical model is developed for calculating the change in surface roughness values in the magnetorheological cylindrical finishing process after consideration of forces as acting on SiC particles. To validate the proposed mathematical model, the experimentation is performed by the magnetorheological cylindrical finishing process for finishing the internal surface of cylindrical hardened ferromagnetic steel workpiece. Results of both i.e. mathematical modeling and experimentation are found to be in close agreement with least percentage error of 1.28%. The developed mathematical model is helpful in predicting the process performance, which proves to be useful for industries dealing with internal finishing like injection molding, gas, and liquid pipes, etc.

Influence of Abrasives in Roller Burnishing Process on Microhardness Using Factorial Design

Burnishing is essentially a cold-working process used to improve properties of the machined surfaces. In present work, an attempt is made to investigate the effect of fine silicon carbide abrasive particles (in the form of a paste) in between roller burnishing tool and cylindrical components of EN24 steel. The mathematical models were developed using 2 4 full factorial design of experiments (DoE) for micro hardness in terms of four variables namely burnishing force, burnishing speed, feed and a number of passes for dry burnishing case and ‘with-paste’ (where burnishing is done using paste) burnishing case. Analysis of variance (ANOVA) is carried out to check the adequacy of the derived models. The results showed that micro hardness of the untreated EN24 steel can be improved by 11% and 18% for dry burnishing case and ‘with-paste’ burnishing case respectively compared to turned components.

Comparisons of the two-body abrasive wear behaviour of four different ferrous microstructures with similar hardness levels

The abrasive wear resistance of four distinct metallurgical steel microstructures – bainite, pearlite, martensite and tempered martensite, with similar hardness levels was investigated. A pin-on-disc tribometer was used to simulate the two-body abrasive condition (i.e. the metallic surface abrading against the silicon carbide abrasive particles) and evaluate the specific wear rate of the microstructures. Each microstructure had a unique response towards the abrasion behaviour and this was largely evident in the friction curve. However, the multi-phase microstructures (i.e. bainite and pearlite) demonstrated better abrasion resistance than the single-phase microstructures (i.e. martensite and tempered martensite). Abrasion induced microstructural changes at the deformed surfaces were studied using sub-surface and topographical techniques. The properties of these layers (i.e. surface profile measurements) determined the amount of material loss for each microstructure. These were directly linked to the single-wear track analysis that highlighted a marked difference in their mode of material removal. Ploughing and wedge formation modes were dominant in the case of bainite and pearlite microstructures, whereas the cutting mode could be attributed to the higher material loss in the single-phase microstructures. The combination of brittle and ductile phases in the multi-phase microstructure matrix could be one of the driving factors for their superior abrasion resistance.

Swirling Abrasive Fluidized Bed Machining: Effect of Process Parameters on Machining Performance

Swirling Abrasive Fluidized Bed Machining (SA-FBM) is a novel variant of Fluidized Bed Machining (FBM). This research focuses on the experiments performed on copper specimens using silicon carbide abrasive particles to investigate the influence of operating parameters such as grain size, superficial velocity, and machining time on metal removal rate, transformation of surface texture, and the surface finish. The study concludes that the surface modification is faster with SA-FBM compared with conventional FBM; the initial roughness conditions of the workpiece have no effect on the maximum possible surface finish; moreover, for faster metal removal, higher superficial velocity, and for better surface finish, fine abrasive grains are preferred.

Polishing Process of Ceramic Tiles - Variation of Contact Pressure

The contact pressure is one of the most important parameter in the industrial polishing process of ceramic tiles. The contact pressure is asically a function of the elasticity moduli of both tile and abrasive tool, the applied load, and also the curvature of the abrasive tool. Due to the wear, this curvature decreases during the polishing process, causing an increase in the contact pressure. The purpose of this work is to research the influence of contact pressure on the evolution of gloss and roughness of the polished ceramic tiles and to improve the quality of generated surface. The variation of curvature was replaced with the direct increment of three different normal forces onto the abrasive tool. It is known from literature that for fine abrasive grits higher tool loads increase gloss gain and decrease roughness. However, there are not many works that research the whole sequence of abrasives for different loads and compare the quality of the final surface. Polishing tests on a laboratory scale CNC-Tribometer have been used to study the industrial polishing process for unglazed porcelain ceramic tiles. Tests were carried out for three different tool loads with a sequence of progressively smaller silicon carbide abrasive particles embedded in a magnesia cement matrix. Tile surface quality was evaluated by roughness and optical gloss. The removed work piece material and the used abrasive were measured with a coordinate measuring machine. The distribution of gloss and roughness of the tile was measured before and during the experiments until a saturation of gloss and roughness for each grit number was achieved, respectively. The topography of the tile was measured before and after the polishing process with particularly grit number. The used abrasives show a general trend of increasing gloss and decreasing roughness during the process. The coarse abrasives caused the major effect on surface roughness and almost no effect on gloss. In opposite finer abrasives caused the major gloss enhancement and almost no effect on surface roughness. The results show the evolution of roughness and gloss for each load as a function of abrasive grit number and polishing time, as well as the material removal rate for each grit number and load.

Surface Finishing of Carbon-Carbon Composites Using Abrasive Flow Machining

Carbon-carbon composites (C/Cs) are widely used in the high-technological applications because of their superior properties compared to the other traditional materials. But the surface finishing of these materials using both conventional and unconventional machining (e.g., abrasive flow machining, AFM) is difficult because of their nonhomogeneity, anisotropy, hardness and intrinsic brittleness. In order to study the feasibility of AFM, 3-D C/Cs were initially ground to a surface roughness value in the range of 0.7 ± 0.1 μm, and then finished using newly reported media containing styrene butadiene rubber as a carrier, silicon carbide (SiC) as abrasives and hydraulic oil as a processing oil. The effects of process parameters, such as abrasive mesh size, extrusion pressure, loading of processing oil and abrasive particles, and the number of cycles on the improvement in surface roughness of the C/C material were studied. The best surface finish was observed at an extrusion pressure of 6 MPa and 150 cycles using a media having 70wt% SiC abrasive particles of 220 mesh size and 12wt% processing oil. Further, the surface texture of the workpieces was studied by scanning electron microscope.

Improving sliding and abrasive wear behaviour of cast A356 and wrought AA7075 aluminium alloys by plasma electrolytic oxidation

An important limitation of aluminium alloys for mechanical applications is their poor tribological behaviour. In this study, surface treatment by plasma electrolytic oxidation (PEO) has been applied to two widely used aluminium alloys: A359 (hypoeutectic Al–Si–Mg) cast alloy and AA7075 (Al–Zn–Mg–Cu) wrought alloy, in order to improve their wear resistance, under sliding and abrasive wear conditions. The main aim of this work was the comparison of the properties and wear resistance of the oxide layers grown under the same PEO treatment conditions on two different aluminium alloys which might be coupled in engineered components. Significant differences in the phase composition, microstructure and mechanical properties measured by microindentation were observed in the oxide layers grown on the two substrates, and were ascribed to the effects of the different compositions and microstructures of the substrate alloys. Abrasion tests were carried out in a micro-scale abrasion (ball-cratering) test, with both alumina and silicon carbide abrasive particles. The results demonstrated the influence of the abrasive material on wear behaviour: whereas relatively aggressive SiC particles gave comparable results for both PEO treated and untreated samples, with the less aggressive Al 2O 3 abrasive the wear rates of the PEO treated samples, for both substrates, were significantly lower than those of the untreated substrates. In unlubricated sliding the PEO treatment significantly increase the wear resistance of both the aluminium alloys, at low applied load. In this condition the wear behaviour of the PEO treated alloys is strongly influenced by the stability of a protective Fe–O transfer layer, generated by wear damage of the steel counterpart. Under high applied loads however, the transfer layer is not stable and the hardness of the PEO layer, as well as the load bearing capacity of the substrate, become the main factors in influencing wear resistance.

Development of surface finish during the polishing of porcelain ceramic tiles

Polishing tests on a laboratory scale have been used to simulate and study the industrial polishing process for unglazed porcelain ceramic tiles. Tile surface quality was assessed in terms of roughness and optical gloss. Tests with a sequence of progressively smaller silicon carbide abrasive particles showed a general trend of decreasing roughness and increasing gloss during the process. The coarser abrasives (larger than 400 grit number) caused the major change in surface roughness, while the finer abrasives (smaller than 400 grit number) produced the major change in gloss. In these materials the maximum gloss achievable by polishing is limited by the porosity of the ceramic. The rate of material removal during polishing with a coarse abrasive obeyed an Archard-type wear law, being linearly proportional to applied load, although load had little effect on the surface roughness attained after different durations of polishing. In contrast, load had a significant effect on gloss, with higher loads leading to higher values of gloss. The development of both roughness and gloss with polishing time is well described by quantitative empirical models involving a simple exponential function. The same model for gloss evolution is also shown to apply to data reported from industrial-scale polishing experiments in previous work.

Micro-scale abrasion and scratch response of PVD coatings at elevated temperatures

Physical vapour deposited (PVD) coatings are often exposed to high temperatures in service, for example, in cutting tool applications, yet laboratory testing of such coatings is usually performed at room temperature. In this work two tribological test methods were used to rank the performance at room temperature and at 350°C in air of four PVD coatings (two TiN coatings of different thickness, TiCN and AlTiN) deposited by steered-arc evaporation on to tool steel substrates. The tests were the widely-used scratch test, and the micro-scale abrasion test, in which a steel ball rotates against the specimen surface in the presence of fine abrasive particles. The methods used to modify the tests to operate at the high temperature are described; in the case of the micro-scale abrasion test, dry silicon carbide abrasive particles were used and the results are compared with those obtained with dry particles at room temperature and with the more usual water-based slurry. Wear volumes in the abrasion test as low as 10 −14 m 3 were measured by optical profilometry. Care was taken to separate the effects of testing at high temperature from any permanent changes in material or interface properties induced by exposure to high temperature. The ranking of the coatings by the abrasion test was very similar under all conditions, although some differences in the relative magnitude of wear resistance were noted. The ranking of the coatings by scratch testing changed significantly with temperature, indicating that scratch testing at room temperature of hard coatings intended for use at high temperature may be misleading.

Abrasive wear behaviour of an Al 2O 3–Al co-continuous composite

The response of an alumina–aluminium co-continuous composite (`C 4') to two types of abrasive wear test has been studied. In this material, the ceramic phase (∼70 vol.%) and the metal phase (∼30% vol.%) form continuous interpenetrating networks. The behaviour of the composite has been compared with that of commercial purity aluminium, sintered glass-bonded alumina, and two conventional particulate reinforced aluminium–alumina MMCs in a micro-scale abrasion test with silicon carbide abrasive particles, and in a rubber wheel abrasion test with silica particles. For abrasion by silica particles, the co-continuous composite material exhibited significantly greater wear resistance than conventional aluminium MMCs with discontinuous alumina reinforcement. For abrasion by silicon carbide particles, C 4 and conventional MMCs showed similar performance. These observations can be explained in terms of the response of the composite phases to deformation by the abrasive particles.

High stress abrasive wear behaviour of aluminium alloy–granite particle composite

The abrasive wear characteristics of aluminium alloy (LM6) and its cast composites dispersed with natural minerals, namely, granite particles, (10 wt.%) have been reported in this study. High stress abrasive wear tests using paper-mounted silicon carbide abrasive particles of various grit sizes were carried out at various applied loads. It was observed that the wear response of the specimens is influenced by the applied load, sliding distance and size of the abrasive particle. Results indicated that the addition of the dispersoid led to an improvement in the abrasion rate of the matrix alloy when abraded against fine abrasive particles over the entire range of applied loads and sliding distances. Similar trends were also observed with coarser abrasives at lower loads. However, at higher load and with coarser abrasive particles, the trend got reversed. Further, the wear rate reduced with sliding distance while the load affected the wear behaviour of the specimens in the opposite manner. These effects were more prominent under severe wear conditions of abrasion (i.e., higher load or coarser abrasive). The specimens characteristics have been explained on the basis of experimental observations.