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Wear Properties (wear + property)
Selected AbstractsStepwise-Graded Si3N4,SiC Ceramics with Improved Wear PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Scott C. Thompson The processing of stepwise graded Si3N4/SiC ceramics by pressureless co-sintering is described. Here, SiC (high elastic modulus, high thermal expansion coefficient) forms the substrate and Si3N4 (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 ,1.7 mm. The resulting Si3N4 contact surface is fine-grained 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 elastic-modulus gradient and the compressive thermal-expansion-mismatch 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 Si3N4 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. [source] Wear Mechanisms of TiB2 and TiB2,TiSi2 at Fretting Contacts with Steel and WC,6 wt% CoINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2010Golla Brahma Raju Unlubricated fretting wear tests on TiB2 and TiB2,5 wt% TiSi2 ceramics against two different mating materials (bearing grade steel and WC,6 wt% Co balls) were performed with a view to understand the counterbody-dependent difference in friction and wear properties. The fretting experiments were conducted systematically by varying load (2,10 N) at an oscillating frequency of 4 Hz and 100 ,m linear stroke, for a duration of 100,000 cycles. Adhesion, abrasion, and three-body wear have been observed as mechanisms of material damage for both the TiB2/steel and TiB2/WC,Co tribosystems. The third body is predominantly characterized as tribochemical layer for TiB2/steel and loose wear debris particles for TiB2/WC,Co tribocouple. An explanation on differences in tribological properties has been provided in reference to the counterbody material as well as microstructure and mechanical properties of flat materials. [source] Friction and wear properties of NBR/PVC compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Xinwu Huang Abstract Acrylonitrial butadiene rubber (NBR)/Polyvinyl chloride (PVC) composites with different PVC content were prepared. The effect of PVC content on the mechanical strength and tribological properties of the NBR/PVC composites was investigated. The morphologies of the worn traces and debris of NBR/PVC composites and worn traces of mating ball were observed using a scanning electron microscope (SEM). It was found that the friction and wear of NBR/PVC was lower than that of NBR without PVC. The NBR/PVC composite with 30% PVC content showed the best synthetic mechanical and tribological properties. The inferior elastic properties and the lesser deformation under the applied load of composites with PVC resulted in hysteric force and adhesion force decrease, which leading to a lower friction and wear of NBR/PVC composites. The frictional failure unit of NBR70/PVC30 composite being smaller should be an important reason of the wear of the composite being lowest. The lubricating effect of PVC played an important role in decreasing the friction coefficient and wear of NBR/PVC composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Stepwise-Graded Si3N4,SiC Ceramics with Improved Wear PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Scott C. Thompson The processing of stepwise graded Si3N4/SiC ceramics by pressureless co-sintering is described. Here, SiC (high elastic modulus, high thermal expansion coefficient) forms the substrate and Si3N4 (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 ,1.7 mm. The resulting Si3N4 contact surface is fine-grained 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 elastic-modulus gradient and the compressive thermal-expansion-mismatch 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 Si3N4 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. [source] Reciprocative sliding friction and wear properties of electrical discharge machined ZrO2 -based compositesLUBRICATION SCIENCE, Issue 9 2009Koenraad Bonny Abstract Hot-pressed, laboratory-made, ZrO2 -based composites with 40 vol. % WC, TiCN or TiN were surface finished by electrical discharge machining in order to compare their reciprocating sliding friction and wear response against WC,6wt%Co cemented carbide in unlubricated conditions. Sliding experiments were performed using a Plint TE77 pin-on-flat wear test rig, revealing a strong impact of the secondary phase on the tribological behaviour of the ZrO2 -based composites. The worn surfaces and wear debris were characterised by scanning electron microscopy, energy dispersive X-ray analysis and surface topography scanning, pointing out abrasion, polishing and adhesion as main wear mechanisms. The most favourable friction and wear characteristics were encountered with ZrO2,WC composites compared to the other grades with equal amount of volumetric secondary phase. Copyright © 2009 John Wiley & Sons, Ltd. [source] The comparison of wear properties of different Fe-based hardfacing alloys in four kinds of testing methodsLUBRICATION SCIENCE, Issue 4 2008E. Badisch Abstract Iron-based hardfacing alloys are widely used to protect machinery equipment. A strong correlation is given between microstructure and chemical composition of welding deposit with the resulting wear behaviour. Concerning precipitation of metallurgical hard phases and synthetic added hard particles, the bonding strength of the hard phases in the metallic matrix seems to play a dominating role to obtain high wear resistance. The main objective of this study was to evaluate the wear behaviour for pure abrasion, combined impact/abrasion and high impact wear, respectively, for four different Fe-based hardfacing alloys. Tests were performed with a standard ASTM G65 dry-sand/rubber-wheel tester. An impeller,tumbler apparatus enabled investigation of impact abrasion wear tests. Additional wear tests with high impact loading were performed on a drop hammer apparatus. Fracture surface analysis was carried out after drop hammer testing and results were correlated with microstructure and interfacial bonding behaviour of precipitations in metallic matrix. Copyright © 2008 John Wiley & Sons, Ltd. [source] Engineering and Design of Wear and Corrosion Resistant PVD Coatings Regarding the Exceptional Properties of Magnesium SubstratesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Holger Hoche Abstract Although magnesium alloys were popular in the first half of the 20th century, the bad corrosion properties prevented their breakthrough in industrial mass production. Since the technology for the production of high purity alloys was introduced in the 1970s, magnesium alloys became more and more in the focus of industrial attention. Today magnesium alloys are state-of-the-art in construction parts in automotive industry. Despite its outstanding properties like good castability, low density and nearly unlimited availability the negative aspects like weak corrosion and wear behaviour still limit the application of magnesiums in industry, due to the need of sufficient surface protection (E. Aghion, B. Bronfin, Mater. Sci. Forum2000, 350,351, 19). Today, plasma electrolytic anodisations are state-of-the-art (H. Haferkamp, "Magnesiumkorrosion,Prozesse, Schutz von Anode und Kathode", in: Moderne Beschichtungsverfahren, F.-W. Bach, T. Duda, Eds., Wiley-VCH, Weinheim 2000, ISBN 3-527-30117-8, 242; M. Thoma, Metalloberfläche1984, 38, 393; T. W. Jelinek, Galvanotechnik2003, 94, 46; A. Kuhn, Galvanotechnik2003, 94, 1114). They provide acceptable corrosion resistance and protect the magnesium from mechanical damage due to their high hardness. On the other hand, their high porosity limits their use in combination with electrochemically noble materials, leading to galvanic corrosion (J. Senf, "Untersuchung und Beschreibung von Magnesiumdruckgusslegierungen unter tribologischer, korrosiver und mechanisch-korrosiver Beanspruchung, Berichte aus der Werkstofftechnik", Shaker Verlag, Germany 2001, ISBN 3-8265-8428-7). In addition, the high surface roughness of the plasma electrolytic anodisations restricts their use in tribological applications, particularly under sliding conditions (H. Hoche, "Grundlegende Untersuchungen zur Entwicklung von PVD-Beschichtungen auf Magnesiumlegierungen im Hinblick auf die Erhöhung der Verschleißbeständigkeit und unter Berücksichtigung des Korrosionsverhaltens", Dissertation, TU-Darmstadt D17, Shaker Verlag, Germany 2004). In order to achieve smooth surfaces with high quality, the PVD technology moves into the centre of interest. Since the 1980s PVD coatings are well established and widely used for different industrial applications, mainly for steel and tool coatings. The authors were the first who carried out serious studies on the development of PVD coatings for magnesium alloys in 1999 (J. Senf, "Untersuchung und Beschreibung von Magnesiumdruckgusslegierungen unter tribologischer, korrosiver und mechanisch-korrosiver Beanspruchung, Berichte aus der Werkstofftechnik", Shaker Verlag, Germany 2001, ISBN 3-8265-8428-7; H. Hoche, "Grundlegende Untersuchungen zur Entwicklung von PVD-Beschichtungen auf Magnesiumlegierungen im Hinblick auf die Erhöhung der Verschleißbeständigkeit und unter Berücksichtigung des Korrosionsverhaltens", Dissertation, TU-Darmstadt D17, Shaker Verlag, Germany 2004). The extensive research activities lead to the recent development of a coating system, which provides both, good wear properties as well as good corrosion behaviour. [source] Wear of the artificial hip joint material under lubricationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009E. P. J. Waters Abstract A study of wear properties of hip-replacement materials, namely high-nitrogen stainless-steel femoral heads and ultra-high molecular weight polyethylene (UHMWPE), was conducted in a non-conforming apparatus using various liquid lubricants. The liquids used were normal saline solution, sodium azide solution, pure ethanol, aqueous hyaluronic acid and aqueous hyaluronic acid/cholesterol and cholesterol palmitate liquid crystal lubricant. Saline solution proved to be unsuitable as a lubricant while sodium azide that was used as a bactericide provided some evidence of mixed lubrication. A bactericide was included to overcome degradation. The aqueous hyaluronic acid exhibited cushion form lubrication as evidenced by retention of the original polymer surface features within the wear indent. Cholesterol addition showed little improvement on the wear properties but massively increased the bacterial activity. Again, inclusion of a bactericide was necessary. Liquid crystal lubricant significantly reduced wear and the atomic force microscope (AFM) showed that the liquid crystal formed protective layers on the counter face surfaces. The sub-surface of the polymer possessed plastic creep under load but low adhesive wear was present. There also was an absence of sub-micron polymer debris. It was concluded that a dramatic reduction in wear could be achieved by incorporation of liquid crystal lubricant in hip-replacement elements. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Influence of filler type and content on properties of styrene-butadiene rubber (SBR) compound reinforced with carbon black or silicaPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2004Sung-Seen Choi Abstract Rubber compounds are filled with reinforcing fillers to improve their physical properties. Carbon black and silica have different surface chemistries to each other. Differences in properties of carbon black- and silica-reinforced styrene-butadiene rubber (SBR) compounds were studied. Variation of properties of carbon black- or silica-filled compounds with the filler content was also investigated. The silica-filled compounds without any coupling agent and dispering agent were prepared to investigate the influence of polar materials-adsorption on the silica surface. Viscosity and crosslink density increased with increase of the filler content. Hardness, modulus, tensile strength, and wear property were improved more and more by increasing the filler content. Viscosity of the silica-filled compound was higher than that of the carbon black-filled one. Cure rate of the silica-filled compound became slower as the filler content increased, while that of the carbon black-filled one became faster. Difference in properties between the carbon black- and silica-filled compounds were explained by the poor silica dispersion and the adsorption of cure accelerator on the silica surface. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||