Wear resistance of hot-pressed Si3N4/SiC micro/nanocomposites sintered with rare-earth oxide additives (original) (raw)
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Effect of Mechanical Properties on Wear Resistance of Si3N4 – SiC Ceramic Composite
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The effect of mechanical properties on wear resistance of Si 3 N 4-SiC composite materials with different portions of SiC strengthening phase was investigated. Properties of monolithic silicon nitride were compared to ceramic composites consisting of Si 3 N 4 matrix with 10 and 20 vol.% SiC. The SiC strengthening phase had a positive effect on the hardness of Si 3 N 4-SiC ceramic composite materials. Wear resistance of tested ceramic materials was mainly influenced by their fracture toughness. The highest wear resistance value was achieved for material with the highest fracture toughness. Worn surfaces of all experimental ceramic materials were damaged by both microcutting and microcracking mechanism. Microcracking was the predominant wear mechanism mainly at ceramic composites. The wear resistance of SiC-Si 3 N 4 ceramic composites can be described by the model W ~ HV/K IC.
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In the present research study, the tribological characterization of pure silicon nitride (Si 3 N 4) and silicon nitride-titanium carbide ceramic-ceramic composites (Si 3 N 4 + 1 wt% TiC and Si 3 N 4 + 2 wt% TiC) was carried out under dry sliding condition. The samples of Silicon nitride and ceramic composite were fabricated through liquid sintering using yttrium oxide, aluminium nitride and optical grade silica as sintering additives. The effect of load on the friction and wear properties of Si 3 N 4 and Si 3 N 4 /TiC composite is studied. Friction and wear tests were performed on a pin on disc tribometer at room temperature. It was observed that the friction coefficient and wear rate decreases with increase in load. Further, the Si 3 N 4 + 2 wt% TiC composite possessed better tribological characteristics among the materials tested.
Journal of the American Ceramic Society, 1990
A Si3N4/TiC composite was previously demonstrated to exhibit improved wear resistance compared to a monolithic Si3N4 because of the formation of a lubricious oxide film containing Ti and Si at 900°C. Further improvements of the composite have been made in this study through additions of Sic whiskers and improved processing. Four materials-Si3N4, Si3N4/TiC, Si3N4/SiCwh, and Si3N4/TiC/SiCwh-were processed to further optimize the wear resistance of Si3N4 through improvements in strength, hardness, fracture toughness, and the coefficient of friction. Oscillatory pin on flat wear tests showed a decrease in the coefficient of friction from -0.7 (Si3N4) to -0.4 with the addition of TIC at temperatures reaching 900°C. Wear track profiles illustrated the absence of appreciable wear on the Tic-containing composites at temperatures above 700°C. Microscopic (SEM) and chemical (AES) characterization of the wear tracks is also included to deduce respective wear and lubricating mechanisms. [
Ceramics International, 2011
Fully densified SiC ceramics were developed from commercially available b-SiC powders using small amount (3 wt%) of AlN-Sc 2 O 3 or AlN-Y 2 O 3 additives by hot pressing at 2050 8C for 6 h in nitrogen atmosphere, and their wear properties were investigated by subjecting to self-mated sliding at different loads (1, 6 and 13 N) under unlubricated conditions. SiC ceramics prepared with 3 wt% AlN-Y 2 O 3 additives consisted of mostly large equi-axed grains with amorphous grain boundary phase of 1.2nmthickness,whereasSiCceramicssinteredwith3wt1.2 nm thickness, whereas SiC ceramics sintered with 3 wt% AlN-Sc 2 O 3 additives showed duplex microstructure of elongated and fine equi-axed grains with clean grain boundary. As the load was increased, the steady state coefficient of friction reduced from 1.2nmthickness,whereasSiCceramicssinteredwith3wt0.6 to $0.2, and wear rate increased from 10 À6 to 10 À5 mm 3 /NÁm. It was observed that the friction did not depend on the additive composition, while less wear was observed for the SiC ceramics sintered with 3 wt% AlN-Sc 2 O 3 additives consisting of clean grain boundary. The material loss was increased with the increased amount of sintering additive to 10 wt%. The worn surface morphology revealed that the material was primarily removed via surface grooving and microcracking at 1 N load, while tribochemical wear dominated at 6 and 13 N loads.
Dry sliding wear behavior of nano-sized SiC pins against SiC and Si3N4 discs
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Micro-and nano-sized hot-pressed silicon carbide pins have been characterized by room-temperature unlubricated disk-on-pin tribological tests on hot-pressed silicon carbide and silicon nitride discs. The mean grain size was shown not to influence the steady state friction coefficient. The mean grain size clearly affected the disc wear rate: the finer was the grain size the lower was the disc wear rate. No impact of the grain size was observed on the pin wear rate. The basic wear mechanisms were grain fracture and fine abrasion. By depth-sensing indentation, it was shown that a possible explanation of the different wear behaviour between micro-and nano-sized silicon carbide are the values of mechanical properties, especially hardness, when they are measured on volumes scaling with the material microstructure.
Wear mechanisms maps of Si3N4/carbon nanotube nanocomposites
IOP Conference Series: Materials Science and Engineering, 2016
Silicon nitride-based nanocomposites with different amount (0, 1, 2 wt%) of multiwall carbon nanotubes (MWCNT) have been prepared by hot isostatic pressing. Tribological tests were carried out at room temperature, in dry sliding condition using pin-ondisc test apparatus, applying different normal loads and sliding speeds. Wear phenomena was analysed by scanning electron microscopic investigations of the wear tracks. Based on the controlling wear mechanisms and wear types two-dimensional wear mechanisms maps were created for all composition of the investigated ceramic nanocomposites.
Stepwise-Graded Si3N4-SiC Ceramics with Improved Wear Properties
Journal of the American Ceramic Society, 2002
The processing of stepwise graded Si 3 N 4 /SiC ceramics by pressureless co-sintering is described. Here, SiC (high elastic modulus, high thermal expansion coefficient) forms the substrate and Si 3 N 4 (low elastic modulus, low thermal expansion coefficient) forms the top contact surface, with a stepwise gradient in composition existing between the two over a depth of ϳ1.7 mm. The resulting Si 3 N 4 contact surface is finegrained and dense, and it contains only 2 vol% yttrium aluminum garnet (YAG) additive. This graded ceramic shows resistance to cone-crack formation under Hertzian indentation, which is attributed to a combined effect of the elasticmodulus gradient and the compressive thermal-expansionmismatch residual stress present at the contact surface. The presence of the residual stress is corroborated and quantified using Vickers indentation tests. The graded ceramic also possesses wear properties that are significantly improved compared with dense, monolithic Si 3 N 4 containing 2 vol% YAG additive. The improved wear resistance is attributed solely to the large compressive stress present at the contact surface. A modification of the simple wear model by Lawn and co-workers is used to rationalize the wear results. Results from this work clearly show that the introduction of surface compressive residual stresses can significantly improve the wear resistance of polycrystalline ceramics, which may have important implications for the design of contact-damage-resistant ceramics. H. M. Chan-contributing editor Manuscript No. 187280.
Friction and wear properties of nano-Si3N4/nano-SiC composite under nanolubricated conditions
Journal of Advanced Ceramics, 2016
Friction and wear behaviors of different concentrations of IF-MoS2 nanoparticles in SAE 20W40 were studied. First of all tribological tests with SAE 20W40 + IF-MoS2 were carried out on a four ball wear test machine as per ASTM D 4172 standard to study its wear properties. Detailed friction and wear studies on cylinder liner and piston ring tribopair were conducted on pin-on-block universal tribometer under lubricated conditions of SAE 20W40+ IF-MoS2. These experimental studies were conducted at different operating parameters to ascertain the influence of nanoadditive on friction and wear of cylinder liner and piston ring tribopair. A minimum coefficient of friction of 0.0772 was observed for 0.5 wt% of IF-MoS2 at normal load of 100 N at sliding velocity of 0.03 m/sec. A substantial reduction of 65 % in the wear of cylinder liner and piston ring tribo-pair was also observed when lubricated with SAE 20W40 and 0.5 wt% of IF-MoS2. Scanning electron microscopy and energy dispersive spectrometry analysis of the worn out surfaces was also carried out to find the causes for observed friction and wear behavior.
Rare-earth element doped Si3N4/SiC micro/nano-composites—RT and HT mechanical properties
Journal of the European Ceramic Society, 2010
Dense Si 3 N 4 /SiC micro/nano-composites with varying grain boundary phase composition were fabricated by hot-pressing under the same conditions. Six different sintering aids () were used. The formation of SiC nano-inclusions was achieved by in situ carbothermal reduction of SiO 2 by C during the sintering process. Room temperature, fracture toughness, hardness and strength tended to increase when the cation radius of the rare-earth element used in the oxide additive decreased (i.e. from La 3+ to Lu 3+ ). The composite material with Lu 2 O 3 sintering additive showed the highest hardness and had reasonably high fracture toughness and strength. The same micro/nano-composite also possessed the highest creep resistance in the temperature range from 1250 • C to 1400 • C and with loads in the range 50-150 MPa.
Characterization and wear behavior of modified silicon nitride
International Journal of Refractory Metals and Hard Materials, 2005
Silicon nitride-based materials are applied to many tribological components because of their superior thermal and mechanical properties and corrosion resistance. The purpose of this study is to investigate the wear performance of modified silicon nitride which contained 3 wt.% La 2 O 3 and 3 wt.% Y 2 O 3 . The relationships between microstructure and mechanical properties have been also addressed. Vickers microhardness and toughness were measured, the later being determined by means of the direct crack measurement method (DCM). Scanning electron microscopy technique (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) was used for the morphological characterization of the samples as well as for the characterization of the wear scars. Wear properties were studied under a load of 10 N by using the ball-on-disk tribometer. AISI 52100 steel balls and balls of WC + 6% Co (6 mm diameter) were used as static counterparts, respectively. Steady state friction coefficients of 0.66 and 0.62 were measured for the tribological pairs WC + 6 % Co/Si 3 N 4 and AISI 52100/Si 3 N 4 , respectively. The wear mechanism was determined in each case, and comparison between the wear performance of the traditional and modified silicon nitride is also presented.