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[en] Thermal spray processes are used for a lot of traditional and innovative applications and their importance is becoming higher and higher. WC/CoCr based thermal spray coatings represent one of the most important class of coatings that find application in a wide range of industrial sectors. This paper will address a review of current applications and characteristics of this kind of coating. The most important spraying processes, namely HVOF (high velocity oxygen fuel) are examined, the characterization of the coatings from the point of view of corrosion and wear resistance is considered. (author)
[en] Highlights: ► WC particle is first used to reinforce AMMCs via ARB. ► Al/WC composites consist of ultrafine grains and numerous dislocations. ► Excellent mechanical properties of Al/WC composites are exhibited. ► Wear property of particle-reinforced AMMCs fabricated via ARB be evaluated firstly. -- Abstract: In the present study, aluminum metal matrix composites (AMMCs) reinforced with tungsten carbide (WC) particles are manufactured through warm accumulative roll bonding (ARB). The composite microstructure shows excellent WC particle distribution in the Al matrices, and no reaction between Al and WC is observed. Compared with the ARBed 1060-Al, the Al/WC composites show a higher number of dislocations, as suggested by the introduction of WC particles. The tensile, hardness, and wear properties of the Al/WC composites are determined. The introduction of 3 vol% WC particles to the Al matrix via the warm ARB process leads to significantly enhanced mechanical properties.
[en] Densification and mechanical characteristics or WC-Co Cemented Carbides, were investigated by dilatometry, Hardness and bending tests, as a function of the two principal micro-structural parameters: the cobalt content and the particle size of carbide crystals. Vickers hardness of the studied compositions showed a linear variation with the increase of the cobalt content. By three point bending, the transverse rupture strenght increases with cobalt content, however, for larger grain size reaches a maximum, eventually reduced by brittle phases and incomplete dispersion. The results of brittle facture tests were statistically analised and fitted better to the 'Weakest Link Model' (Weibull distribution) than the 'Chain Model' (Gaussian distribution). (author)
[pt]As caracteristicas mecanicas e de densificacao de ligas WC-Co, foram estudadas atraves de ensaios de dilatometria, flexao e dureza, em funcao dos dois principais parametros micro-estruturais: teor de Cobalto e tamanho de particula do carboneto. A dureza HV variou linearmente com o aumento do teor de Co. No ensaio de flexao sob tres pontos a resistencia a ruptura transversal aumentou com teores crescentes do cobalto. Na granulacao grosseira atingiu um maximo, eventualmente reduzido por fases frageis e uma dispersao incompleta. Os resultados dos ensaios de fratura fragil analisados estatisticamente, se ajustaram melhor a um modelo do elo mais fraco, distribuicao de Weibull, do que ao modelo de encadeamento da distribuicao de Gauss. (autor)
[en] Highlights: → The microstructure of Ti-48Al alloy changes under high pressure. → With increasing pressure, the amount of γs phase decreases. → High pressure leads to the decreasing of lamellar spacing. → The nanohardness of lamellar structure increases with pressure. -- Abstract: In this work the microstructure and nanohardness of Ti-48 at.%Al alloy solidified under different pressures (normal pressure, 2 GPa, 4 GPa) were experimental investigated by using a tungsten-carbide six-anvil apparatus. The results indicate that high pressure does not change the phase constitution of Ti-48 at.%Al alloy. However, the microstructure changes under high pressure. With increasing pressure, the volume fraction of interdendritic γ (γs) phase decreases and Al concentration in lamellae increases. When the pressure is 4 GPa, there is only a little γs embedded in lamellar structure. The volume fraction of γs phase is approximately 17.0% for normal pressure, 8.73% for 2 GPa, 0.69% for 4 GPa. The lamellar spacings also decrease with pressure, which are 495 nm, 345 nm, 227 nm under normal pressure, 2 GPa, 4 GPa, respectively. The change in nanohardness was discussed based on the microstructural observations. It shows a certain increase of the nanohardness as the pressure increases from normal pressure to 4 GPa. When the pressure is 4 GPa, the nanohardness increases by 50.2% compared with that of normal pressure.
[en] Present work focuses on study of influence of E-glass fibre and Tungsten Carbide hybrid reinforcement on thermal conductivity of Al7075 based hybrid composite. Hybrid composites with two different reinforcements were synthesized using liquid metallurgy route. Developed hybrid composites were subjected to T6 heat treatment process. The impacts of hybrid reinforcements and heat treatment on microstructure and thermal conductivity have been investigated. ASTM E1530 standard test procedure was followed to determine the thermal conductivity of hybrid composites. Microstructure studies on composites have revealed a fairly uniform dispersion of E-glass fibre and Tungsten carbide. An excellent union between matrix and reinforced particles have been observed in all the hybrid composites studied. Thermal conductivity of hybrid composites decreases with reinforcements and increases with increase in temperature. Heat treatment has significantly improved thermal conductivity of hybrid composites. (paper)
[en] In this experimental work dry turning process carried out on EN47 spring steel with coated tungsten carbide tool insert with 0.8 mm nose radius are optimized by using statistical technique. Experiments were conducted at three different cutting speeds (625, 796 and 1250 rpm) with three different feed rates (0.046, 0.062 and 0.093 mm/rev) and depth of cuts (0.2, 0.3 and 0.4 mm). Experiments are conducted based on full factorial design (FFD) 33 three factors and three levels. Analysis of variance is used to identify significant factor for each output response. The result reveals that feed rate is the most significant factor influencing on cutting force followed by depth of cut and cutting speed having less significance. Optimum machining condition for cutting force obtained from the statistical technique. Tool wear measurements are performed with optimum condition of Vc = 796 rpm, ap = 0.2 mm, f = 0.046 mm/rev. The minimum tool wear observed as 0.086 mm with 5 min machining. Analysis of tool wear was done by confocal microscope it was observed that tool wear increases with increasing cutting time. (paper)