Papers by Author: Yeong Sik Kim

Abstract: Thermal spray technology allows providing wear-resistant coating on the surface of mechanical components. In this study, wear characteristics of thermally sprayed Al/SiC composite coatings were evaluated. These Al/SiC composite coatings reinforced with SiC particles were fabricated on Al 6061 substrate by thermal spray process. Dry sliding wear tests were performed using the varied sliding speeds and applied loads. Wear behavior of these Al/SiC composite coatings were investigated using scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDX) and X-ray diffraction(XRD).

Abstract: Thermal spray technology provides wear-resistant coating on the surface of mechanical components. In this study, wear characteristics of SiCp reinforced Al matrix composite coatings were evaluated. SiCp reinforced Al matrix composite coatings were fabricated using the mixed powders which have different fraction of the SiC reinforcement, 0, 20, 40 and 60 vol% on Al 6061 substrate by thermal spray process. Dry sliding wear tests were performed on these coatings using varied sliding speeds and applied loads. Wear behavior of these Al-based composite coatings were investigated using scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDX) and X-ray diffraction(XRD). The composites coatings reinforced with 40 vol% of SiC particles showed the most excellent wear resistance. Although the wear rate increased according to the increase in the applied load, it decreased according to the increase in the sliding speed. The major wear behavior of the SiCp reinforced Al matrix composite coatings is transferred from the adhesive wear to the abrasive wear according to the increase in the sliding speed and the applied load. These results were significantly influenced by the formation of mechanical mixed layer(MML).

Abstract: In this study, microstructure and wear behavior of thermally sprayed Fe-based alloy coatings were investigated. Fe-based alloy coatings were formed on a carbon steel substrate and then heat-treated at temperature of 700 oC for 20 minutes. Dry sliding wear tests were performed using the sliding speeds of 0.4 and 0.8 m/s, the applied loads of 3 and 6 N. Microstructure and wear behavior of as-sprayed and heat-treated Fe-based amorphous coatings were studied using a scanning electron microscope(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD).

Abstract: SiC particulates reinforced Al matrix composites were fabricated by thermal spray process, and the dry sliding wear behavior against four different counterparts was investigated under a varying of the sliding speed and the applied load conditions. Al/SiC composites were fabricated by flame spraying, and the dry sliding wear tests were performed using the sliding speed of 0.4 m/s and 0.8 m/s at the applied load of 3 N. Sliding distance was kept at 1000 m for all the tests. Al2O3, ZrO2, Si3N4 and AISI 52100 balls were used as the counterparts. Wear tracks on the Al/SiC composites were investigated using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear behavior of Al/SiC composites was much influenced by counterpart materials.

Abstract: This study aims at investigating the effect of the sliding speed and the applied load on the dry sliding wear behavior of thermally sprayed Ni-based self-flux alloy coating. Ni-based self-flux alloy powders were flame-sprayed onto a carbon steel substrate and then these coatings were heat-treated at temperature of 1000 oC. Dry sliding wear tests were performed using the sliding speeds of 0.2, 0.4, 0.6 and 0.8 m/s and the applied loads of 5, 10, 15 and 20 N. AISI 52100 ball (diameter 8 mm) was used as counterpart material. Wear behavior of Ni-based self-flux alloy coatings was studied using a scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that microstructure and wear behavior of the Ni-based self-flux alloy coatings were much influenced by the sliding speed and the applied load.

Abstract: SiC particulates reinforced with Al matrix composites were fabricated using a thermal spray process. In addition, the dry sliding wear behavior was investigated using various sliding speeds and applied loads. Premixed Al and SiC powder was sprayed onto an Al6061 substrate by flame spraying, and dry sliding wear tests were performed under varying sliding speed and applied load conditions. Wear behavior of the composites were studied using a scanning electron microscope(SEM), X-ray diffraction(XRD) and a surface roughness tester.

Abstract: The effects of processing parameters such as addition type and Mg content on the fabrication of Al2O3p/Al composites by in-situ reaction process of molten Al were investigated in terms of infiltration behavior of molten Al and the variation of the microstructure and hardness of the composites. It was ascertained that additional Mg content is the most important parameter for the infiltration of molten Al. Furthermore, increase in additional Mg content and processing temperature resulted in a high infiltration ratio of molten Al and a high hardness value of the composites. However, these caused a greater scatter of the hardness value of the composites due to the nonuniform dispersion of the reinforcement phase, which arose from an excessive reaction of Mg.

Abstract: SiC particulates reinforced metal matrix composites (MMCs) were fabricated by two different processes, pressureless infiltration and thermal spray. 10, 20, 30, 40 and 50 vol% SiC reinforced Al matrix composites (AMCs) were fabricated by these two processes. For these AMCs, dry sliding wear tests were performed under a normal load of 3 N, a constant sliding speed of 0.2 m/s and sliding distance of 1000 m against an AISI 52100 ball. Microstructures and wear behavior were studied by means of scanning electron microscope (SEM) and electron probe micro-analysis (EPMA).

Abstract: An experimental study of dissimilar friction welding was conducted using 15mm diameter solid bar in chrome molybdenum steel (SCM440) to carbon steel (S45C) not only to optimize the friction welding conditions, but also to investigate the fatigue performance. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and HAZ, and microstructure investigations. In this study, the specimens were tested as welded. For fatigue strength, the notched specimens for the optimal conditions were rotary bending fatigue tested. The results were compared with S-N curves for the base metals.