The comparative performance of glass-epoxy (G-E) composites, having rubber in one instance and graphite of two differing levels in epoxy matrix resin in the other, during sliding in pin-on-disc type set up under varying load and sliding velocities is reported in this investigation. Besides conventional weighing, determination of coefficient of friction (µ) and examination of the worn surface features by scanning electron microscope (SEM) were undertaken to have an overall picture of the tribological behaviour of the filled composites.For increased load and sliding velocity situations, higher wear loss was recorded. In case of rubber-bearing samples, the coefficient of friction values show an increasing trend with a rise in load and a decrease in their values for increase in velocity. The coefficient of friction increases with increase in load for a fixed velocity in higher graphite bearing samples. However, G-E composite having either lower or higher amount of graphite shows, respectively, either a decrease or increase in coefficient of friction with an increase in sliding velocity for a fixed load. Thus, the higher graphite bearing G-E composite records lower coefficient of friction for any combination of load and velocity. These are explained on the basis of frictional drag forces and formation of graphite film on the surface. Some of these deductions are supplemented by SEM observations.
The performance of filled fiber reinforced polymer composites is generally determined on the basis of the interface attraction of filler, fiber, and polymer. In the present investigation, the effects of SiC particles as fillers in glass—epoxy (G—E) composite systems on the mechanical and tribological properties have been discussed. The composites employed in the present study have been fabricated using hand lay-up technique. The mechanical properties such as tensile strength, tensile modulus, elongation at break, flexural strength, and hardness have been investigated in accordance with ASTM standards. From the experimental investigation, it was found that the mechanical properties of the G—E composite increased with the inclusion of SiC filler. The dry slide wear test results of SiC-G—E composite show lower slide wear losses irrespective of the load/sliding velocity when compared to G—E composite. Some of these observations are supplemented by scanning electron microscopic (SEM) observations. Further, wear of the matrix, breakage of reinforcing fibers, matrix debris formation, and interface separation were observed. SEM microphotographs of the tensile fractured samples revealed the typical aspects of the fractured surfaces. The failure modes of the tensile fractured surfaces were evaluated and showed good agreement with the literature.
The hydro plants utilizing silt-laden water for power generation suffer from severe metal wastage due to particle-induced erosion and cavitation. High-velocity oxy-fuel process (HVOF)-based coatings is widely applied to improve the erosion life. The process parameters such as particle velocity, size, powder feed rate, temperature, affect their mechanical properties. The high-velocity air fuel (HVAF) technology, with higher particle velocities and lower spray temperatures, gives dense and substantially nonoxidized coating. In the present study, the cavitation resistance of 86WC-10Co4Cr-type HVOF coating processed at 680 m/s spray particle velocity was compared with HVAF coatings made at 895, 960, and 1010 m/s. The properties such as porosity, hardness, indentation toughness, and cavitation resistance were investigated. The surface damage morphology has been analyzed in SEM. The cohesion between different layers has been examined qualitatively through scratch depth measurements across the cross section. The HVAF coatings have shown a lower porosity, higher hardness, and superior cavitation resistance. Delamination, extensive cracking of the matrix interface, and detachment of the WC grains were observed in HVOF coating. The rate of metal loss is low in HVAF coatings implying that process parameters play a vital role in achieving improved cavitation resistance.
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