ABSTRACT
In the current work, several composites made with fly ash reinforcements are used to conduct electrical discharge machining (EDM) on stainless steel that is commercially accessible. Four composites were prepared with 2.5 to 10% reinforcement of fly ash with steps of 2.5%, copper is used as the matrix material. The specimens were created using the powder metallurgy method, which involved compaction pressures of 450 MPa and 900 °C for 90 min of sintering. The prepared composites are used as the electrode tool for EDM. EDM studies were carried out at two different current amplitudes (5A and 15A) by maintaining the Pulse on time (100 µs), Pulse off time (50 µs), and the depth of machining as 2 mm. The findings show that the addition of more fly ash to the copper matrix increased the material removal rate when cutting the SS304 plate and had a negative impact on the tool. The composite loses its ability to transfer heat during machining as the level of fly ash increases, raising the temperature in the copper matrix and causing the copper to melt more quickly at the electrode interface during machining, leading to increased electrode wear. While tool life was reduced because of the increase in current amplitude, machinability was enhanced.
ABSTRACT
Due to their excellent synergistic properties, Aluminum Matrix Composites (AMC) have achieved a high degree of prominence in different industries. In addition to strength, the wear resistance of materials is also an important criterion for numerous applications. The wear resistance depends on the surface topography as well as the working conditions of the interacting parts. Therefore, extensive experiments are being conducted to improve the suitability of engineering materials (including AMC) for different applications. This paper presents research on manufactured aluminum metal matrix composites reinforced with 10 wt.% of Al2SiO5 (aluminum sillimanite). The manufactured and prepared samples were subjected to surface topography measurements and to tribological studies both with and without lubricant using a block-on-ring tester. Based on the results, analyses of the surface topography (i.e., surface roughness parameters, Abbott-Firestone curve, and surface defects) as well as of the tribological characteristics (i.a. friction coefficient, linear wear, and wear intensity) were performed. Differences in the surface topography of the manufactured elements were shown. The surface topography had a significant impact on tribological characteristics of the sliding joints in the tests where lubrication was and was not used. Better tribological characteristics were obtained for the surfaces characterized by greater roughness (determined on the basis of both the profile and surface texture parameters). In the case of tribological tests with lubrication, the friction coefficient as well as the wear intensity was significantly lower compared to tribological tests without lubrication. However, lower values of the friction coefficient and wear intensity were still recorded for the surfaces that were characterized by greater roughness. The obtained results showed that it is important to analyze the surface topography because surface characteristics influence tribological properties.
ABSTRACT
This paper presents the results of studies to understand the influence of hybridisation on mechanical and tribological behaviour as well as dry sliding wear of aluminium metal matrix composites. Sillimanite and boron carbide (B4C) were used as primary and secondary reinforcements and pure aluminium was used as the matrix material. The composite was fabricated by using a vacuum assisted stir casting process. Different research instruments were used, including a scanning electron microscope with EDX spectrometer, a surface measurement device, a thermal image analyser, as well as a tribotester. The results show that tensile, impact strength and hardness of the hybridised composites are superior (a step ahead) than unreinforced and primary composites. The wear behaviour of the fabricated specimens was tested for the dry sliding wear behaviour under the load range of 10-50 N with the steps of 20 N for the sliding velocities 0.75, 1.5 and 2.25 m/s over a distance of 1000 m. The wear rate increased with load and decreased as the wt.% of reinforcement increased. The wear rate of the composite with 10 wt.% Al2SiO5 was approximately 44% lower than that of the composite with 5 wt.% Al2SiO5. The same dependence was noted for hybrid composite (5 wt.% Al2SiO5 + 5 wt.% B4C)-the wear rate was approximately 50.8% lower than that of the composite with 5 wt.% Al2SiO5 under the same test condition. The friction coefficient decreased as the weight percentage of the reinforcement (Al2SiO5 and B4C) increased due to the uniform distribution of the reinforcement on the surface of the composites. The main wear mechanism of the studied materials was abrasion wear. The wear mechanism of the composite had tribochemical type. It involved the oxidation and transfer of the material, which formed protective tribolayers ensuring an additional sliding process. The mechanism that played the main role in the wear process of the composites was a combination of abrasive, adhesive and oxidative wear.
