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고에너지 전자빔 투사방법으로 제조된 VC/탄소강 표면합금화 재료의 미세조직 형성과 물성 향상
魚光俊,李聖鶴 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.4
The present study is concerned with the microstructural evolution and property improvement of VC/ carbon steel surface-alloyed materials fabricated by high-energy electron-beam irradiation. The mixtures of VC powders and flux (50%MgO-50%CaO or CaF_2) were placed on a plain carbon steel substrate, and then electron beam was irradiated on these mixtures using an electron beam accelerator. The surface-alloyed layers of 1.2∼3 ㎜ in thickness were homogeneously formed without defects, and contained a large amount (up to 10 vol.%) of VC precipitates in the bainitic or martensitic matrix. This microstructural modification including the formation of hard precipitates and hardened matrix in the surface-alloyed layers improved hardness and wear resistance. Particularly in the surface-alloyed material fabricated with the lower input energy density, the wear resistance was greatly enhanced over the steel substrate because of the increased size and volume fraction of VC particles, although the thickness of the surface-alloyed layer decreased. Microstructural modifications including melting, solidification, precipitation, and phase transformation processes of the surface-alloyed layer could also be explained from a thermal transfer modeling and a Fe-V-C ternary phase diagram.
어광준,Barton Arkhurst,김일현,김현길,김정한 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.6
This study investigated the feasibility of a direct energy deposition process for fabrication of oxide dispersionstrengthened steel cladding. The effect of the laser working power and scan speed on the microstructural stabilityof oxide nanoparticles in the deposition layer was examined. Y-Ti-O type oxide nanoparticles with a mean diameterof 45 nm were successfully dispersed by the laser deposition process. The laser working power significantlyaffected nanoparticle size and number density. A high laser power with a low scan speed seriously induced particlecoarsening and agglomeration. Compared with bulk oxide dispersion strengthened steel, the hardness of the laserdeposition layer was much lower because of a relatively coarse particle and grain size. Formation mechanism ofnanoparticles during laser deposition was discussed.
대기 플라즈마 용사에 의한 Al-SiC 복합재료 판재의 제조에 미치는 공정변수의 영향
어광준,강석봉,양병모 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.6
Increased electronic packaging density requires thermal management materials with high thermal conductivities and low coefficients of thermal expansion (CTEs) matching those of ceramic substrates or semiconductors. Recently, metal matrix composites (MMCs) have been developed, which provide unique combination of properties that make them candidates for thermal management materials. Most of conventional processes to fabricate MMCs have complicated steps that reduce the cost effectiveness, such as the infiltration process requiring a preform preparation and long process time. Plasma spraying can be adopted to produce MMCs in a flexible and cost effective manner. In this study, SiC particles reinforced Al matrix composites were fabricated by atmospheric plasma spraying method. Al and SiC powders were blended and sprayed with plasma arc power. SiC were uniformly dispersed in the Al matrix with a volume fraction of up to 46%. There were also pores in the composite with a range of 1.8∼12 vol.%, which could be tailored by process parameters. The experimental CTEs showed 13.5∼17.6×10^-6/℃ for the Al-SiC composite containing about 40 vol.% SiC, which were matched well with the predicted ones.