용사법에 의한 Al/SiC 복합재료의 제조 및 Tribology 특성에 관한 연구

Abstract

Metal matrix composites(MMC) is fabricated by various processes but, these processes have some disadvantages such as limit of size, concentration of reinforcements, generation of reaction products, high manufacturing cost, and others. On the other hand, thermal spray process has some advantages such as, it could fabricate MMC on surface and it is a relatively more economical and fast process than the other processes. For these reasons, lots of researches of fabrication of MMC by Thermal spray process have been reported. In industry, design of optimal process is carried out by user's expedience or trials and errors without statical analysis and so, MMC coatings have problem about durability and reliability. Therefore, in this study, statistical method was applied to design of optimal process for fabrication of Al/SiC composites by thermal spray process. The design of optimal process for thermal-sprayed Al/SiC composites has been designed by L9(34) orthogonal array and analysis of variance(ANOVA). Al/SiC composites was fabricated by flame spray process on steel substrate. The hardness of composites were measured using micro-vickers hardness tester, and these results were analyzed by ANOVA. The ANOVA results showed that the oxygen gas flow, powder feed rate and spray distance affect on the hardness of the Al/SiC composites. From the ANOVA results, the optimal combination of the flame spray parameters could be extracted. It was considered that experimental design using orthogonal array and ANOVA was efficient to determine optimal parametet of thermal-sprayed Al/SiC composites. And then, to study the wear behavior of Al/SiC composites by thermal spray process, first, Al/SiC composites coating with different SiC volume fractions were fabricated by thermal spray process. And the dry sliding wear test were performed on these composites using the applied load of 10 N, rotational speed of 30 rpm, radius of rotation 15 mm and 1000 cycles. Wear tracks on the Al/SiC composites were investigated using scanning electron microscope(SEM) and energy dispersive spectroscopy (EDS). It was observed that wear behavior of Al/SiC composites and formation of MML was changed dramatically according to reinforcement volume fraction. Second, Al/SiC composites were fabricated by thermal spray process, and the dry sliding wear tests were performed using the various sliding speed of 10, 30, 60 and 90 rpm through 1000 cycles. The applied load was 10 N and radius of wear track was 15 mm. Wear tracks on the Al/SiC composites were investigated using SEM and EDS. In the case of sliding speed of 10 rpm, adhesive wear behavior caused by plastic deformation of composite surface was observed. In the cases of sliding speed of 30, 60, 90 rpm, abrasive wear behavior on the adhered layer formed by debris was observed. Dry sliding wear tests were performed on these composites using four different applied loads, as 5, 10, 15 and 20 N. The wear rate of Al/SiC composites decreased according to the increase in the applied load. The dominant wear behavior of the Al/SiC composites transferred from the adhesive wear to the abrasive wear according to the increase in the applied load. Through this study, it was found that the wear behavior of Al/SiC composites was much influenced by sliding speed and applied load.