Harun Mindivan

Tribological Behaviour of Combined Coatings Deposited on Aluminium

In this paper the tribological performance of oxide (Cr2O3, ZrO2CaO and Al203) and combined coatings applied on a commercially pure aluminum sheet were presented. Combined coatings were produced by applying Polytetrafluoroethylene (PTFE) film on the oxide coatings. Among the oxide coatings Cr2O3 exhibited the highest and Al2O3 exhibited the lowest wear resistance, in accordance with their hardness. Combined coatings exhibited superior wear resistance than oxide coatings even at heavy wear testing conditions.

Mechanical and tribological performances of polypropylene composites containing multi-walled carbon nanotubes

Polypropylene (PP)-based composites filled with as-received carbon nanotubes (ASCNTs) and purified carbon nanotubes (PCNTs) at different weight percentages were prepared using twin-screw extrusion and injection moulding. The effects of CNT content and purification procedure on the mechanical properties and wear resistance were examined. The results showed that microhardness, Young’s modulus, tensile strength, and wear resistance values of the composites increased after purification procedure compared to the ASCNT-based composites, due to the fact that the enhanced interactions between CNT and PP improved the load transfer efficiency from PP to CNTs. For the composites prepared with both ASCNT and PCNT, as the loading of the CNTs increased, improved mechanical properties and wear resistance were observed. However, the mechanical properties and wear resistance decreased when the CNT content exceeded 0.8 wt.% due to agglomeration of CNTs.

Influence of retrogression and re-ageing on the mechanical and corrosion properties of 7039 aluminium alloy

The effect of T6 and retrogression and re-ageing (RRA) treatments on the corrosion and mechanical properties of a 7039 Al alloy was examined. T6- and RRA-tempered alloys exhibited a similar intergranular corrosion resistance for a retrogression time of 3 min at 220 °C. The results revealed that an RRA-tempered alloy (3 min retrogression at 220 °C followed by re-ageing) exhibited a higher hardness and strength and a lower ductility and toughness than a T6-tempered alloy with a significant improvement in the stress corrosion cracking resistance.

Mechanical Properties of Polypropylene Based Composites Reinforced with B4C

The present work aims to compare the mechanical properties of Polypropylene (PP) based composites reinforced with B4C. Maleic Anhydride Modified Polypropylene (MAPP) was added to improve the B4C-matrix interphase. Processing has been carried out by twin-screw extrusion and injection molding. By adding the B4C particles to the PP and PP+MAPP matrix, the yield strength, shore D hardness, microhardness and relative scratch resistance increased gradually, but PP+MAPP/B4C composites showed better overall mechanical properties than the PP/B4C composites. However, elongation at break values occurred for all composites dropped with the B4C content, and PP+MAPP/B4C composites exhibited lower elongations at break than PP/B4C composites.

Tribological Performance of Ceramic Coatings Deposited on Polymer Substrates

In this study, tribological performance of ceramic coatings (Cr2O3, Al2O3TiO2 and ZrO2CaO) deposited on commercial poly ethyleneterephthalate have been examined by rubbing Al2O3 balls thereon. The Cr2O3 coating exhibited the greatest hardness and wear resitance in comparison to Al2O3TiO2 and ZrO2CaO coatings. The wear resistance of the coatings increased with increasing hardness. Introduction Polymers potentially feature great advantages in several industrial applications due to their low specific weight, low cost and ease of design. However, high temperatures and harsh tribological conditions limit their use in certain engineering applications. The service performance of polymeric machine elements and components such as prostheses, plastic molds, composites, can be improved by overlaying hard ceramic coatings [1]. Many studies have been performed to elucidate the tribological properties of vacuum arc [2,3], physical vapour deposited metal/nitride coatings [4,5] and thermal spray deposited ceramic coatings [6] on polymer substrates. In contrast, publications related to the tribological properties of flame spray deposited hard ceramic coatings on polymer substrate are scarce. In this study we aimed to examine the tribological performance of ceramic coatings deposited on polymer substrate. Experimental Commercial polyethyleneterephthalate (PET) was used as the substrate material. The Al2O3TiO2, ZrO2CaO and Al2O3 powders used were provided by Sulzermetco. In the present investigation, Cr2O3, Al2O3TiO2 and ZrO2CaO coatings were deposited on the substrate by the flame spray technique. Some physico-chemical specifications of these coating powders are listed in Table 1. Table 1. Properties of coating powders used. Code Chemistry Particle size (μm) Morphology Metco 136CP Cr2O3-5 SiO2-3 TiO2 -90+16 Clad Metco 130 Al2O3-13 TiO2 -30+5 Clad Metco 201NS ZrO2-5 CaO-0.5 Al2O30.4 SiO2-1.1 other oxides -53+11 Angular / Blocky, Fused and Crushed The coatings were characterized using thickness, roughness and hardness measurements. The thickness of the coatings was measured from the cross sections of the samples by a light optical microscope. Surface roughness of the coatings was determined by an optical profilometer, Perthometer S8P. Hardness measurements were conducted on the coatings under an indentation load of 300 g in a Vickers indenter. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 581-584 doi:10.4028/www.scientific.net/KEM.264-268.581

Wear Behavior of SiC, Cr3 C2 and WC Doped Alumina

In this study, the wear behavior of the pure and carbide (SiC, Cr3C2, and WC) doped alumina was investigated. Carbide doping increased the hardness and improved the wear resistance, significantly. WC doped alumina exhibited the highest hardness and wear resistance. Introduction Engineering ceramics are widely used in wear related applications such as extraction, processing, conveying and dust collection equipments in mining and mineral industry, as well as some structural rotating parts. Due to its low cost, rigid structure and capability to retain smooth surfaces over a broad range of contacts, alumina is the preferred ceramic for seals and bearings. Many studies have been performed to elucidate the influence of speed [1,2], load [1,3,4,5], temperature [6], environment [7,8] and microstructure [9,10] on wear behaviour of alumina. However, publications related with wear of carbide doped alumina are scarce. In this study we investigated the tribological performance of SiC, Cr3C2 and WC doped alumina. Experimental The alumina powder utilized in the present investigation was Alcoa (SG3000) product having particle size of 0.3-0.5 μm with purity higher than 99.6 %. Cylindrical compacts (17.2 mm high and 6 mm diameter) were uniaxially pressed from alumina powder at a pressure of 125 MPa. Compacts were then embedded in SiC, Cr3C2 and WC powders. The amount of carbide doping was 0.75 %. The SiC powders having particle size of 0.7-1.3 μm and a purity higher than 99.5 % were supplied from Superior Graphite Company. The WC and Cr3C2 powders were Herman C. Stark’s product with particle size of 2 – 4 μm and purity higher than 99 %. Pure and carbide (SiC, Cr3C2 and WC) doped alumina compacts were sintered at 1500°C for one hour in argon atmosphere. Mechanical properties of the compacts were examined by hardness measurements and wear tests. Hardness of the compacts were measured with a Fischercope ultramicrohardness tester using Vickers type indenter under the load of 1 N. Wear tests were carried out at normal atmospheric conditions (room temperature and 40 % relative humidity) on a reciprocating wear tester under normal load of 20 N using 10 mm diameter Al2O3 balls. The stroke of the balls on the surface of the samples was 10 mm with sliding speed of 0.02 m/s. Friction force was continuously recorded by a computer for total test time of 170 min. After the wear test, the wear tracks developed on the surfaces of the samples were detected by a profilometer. Wear of the samples and the counterface balls were examined by a scanning electron microscope and a light optical microscope, respectively. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 469-472 doi:10.4028/www.scientific.net/KEM.264-268.469

Surface properties and tribocorrosion behaviour of a thermal sprayed martensitic stainless steel coating after pulsed plasma nitriding process

Abstract In this work, the effects of pulsed plasma nitriding on HVOF-sprayed martensitic stainless steel coating were investigated. Martensitic stainless steel coating was pulsed plasma nitrided at 793 K under 0.00025 MPa pressure for 43200 s in a gas mixture of 75% N2 and 25% H2. The pulsed plasma nitriding resulted in not only an increase in the surface hardness, but also improvement of dry sliding wear and tribocorrosion resistance of the HVOF sprayed martensitic stainless steel coating because of the Cr, Fe3, and Fe4 N phases. However, the corrosion resistance of the HVOF-sprayed martensitic stainless steel decreased notably by nitriding process.

Hot Extruded Carbon Nanotube Reinforced Magnesium Matrix Composites and its Microstructure, Mechanical and Corrosion Properties

Carbon nanotube (CNT) reinforced magnesium (Mg) matrix composite rod was successfully fabricated by mechanical ball milling followed by hot extrusion processes. CNTs used were multi-wall carbon nanotubes (MWCNTs). The starting Mg chips were ball-milled under argon atmosphere for 3 h to coat the surface of Mg chips with the pretreated MWCNTs. The CNT-coated Mg chips were then mixed with aluminum (Al) powder at the compositions of Mg-6 wt.% Al-x wt.% CNT (x = 0.5, 1, 2 and 4). The mixture was cold compacted and finally hot extruded.

Microstructure and Mechanical Properties of Dual Matrix Aluminium- Fly Ash Composites Processed via Cryomilling, Cold Compaction and Hot Extrusion

Abstract AA6061/Al alloy chips of different size and fly ash particles have been recycled using the solid state process. The effect of chip size and fly ash content on the microstructure, mechanical and wear properties of the recycled AA6061/Al two phase composites were investigated. Microstructural characterization revealed a uniform distribution of fly ash particles in recycled composites with fine chips and a good interface between fly ash particulates and AA6061/Al two phase matrixes. According to mechanical and wear results, the incorporation of fly ash particles in the AA6061/Al two phase matrix caused reasonable increase in hardness, compressive strength, and wear resistance. On the recycled composites fine chips, the destructive action of the steel ball was very limited compared to that of the Al 2O3 ball.

Fly Ash Particle Reinforced AA6061 Composites Produced by Recycling of Aluminum Chips and Fly Ash Particles

In this work, the re-use of aluminum AA6061 chips and fly ash particles by solid-state processes (cryomilling, cold compaction and hot extrusion) is presented. The process was performed in following steps: comminuting of chips, cryomilling of comminuted chips, aluminum powders and fly ash particles, cold pressing-hot extrusion approach without sintering step. Comparative analysis of the recycled composites with fine and coarse granulated chips was focused on mechanical properties and correlated to microstructural features. The density and electrical conductivity of the recycled composites are lower than those of the unreinforced aluminum alloy due to the presence of fly ash particles. Regarding mechanical properties, the recycled composites with coarse granulated chips showed higher hardness and compressive strength than the recycled composites with fine granulated chips, but the compressive strength of the recycled composites with coarse granulated chips decreased with the increase of fly ash content.