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최한신,박진수 한국분말재료학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.5
Additive manufacturing technology is recognized as an optimal technology for mass-customized distributed production because it can yield products with high design freedom by applying an automated production system. However, the introduction of novel technologies to the additive manufacturing industry is generally delayed, and technology uncertainty has been pointed out as one of the main causes. This paper presents the results of the research and analysis of current standardization trends that are related to additive manufacturing by examining the hierarchical structure of the quality system along with the various industry and evaluation standards. Consequently, it was confirmed that the currently unfolding standardization does not sufficiently reflect the characteristics of additive manufacturing technology, and rather can become a barrier to entry for market participants or an element that suppresses the lateral shearing ability of additive manufacturing technology.
Responses of an atmospheric plasma sprayed (APS) alumina-titania coating to scratch wear
최한신,이창희 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.3
An alumina-titania composite coating was produced using a thermal plasma spraying coating process. As-sprayed coating microstructures were observed using scanning electron microscopy and energy dispersive spectroscopy. A scratch test was conducted on the finely-polished coating under conditions of constant loading speed and moving rate. Acoustic emissions as well as scratching coefficient were measured during scratching. During the cyclic scratching, the APS coating showed fatigue. The transition from plastic deformation to fracture was time-dependent and it was also accelerated with an increase of the applied normal load. During plastic deformation, fine wear debris resulted from grain crushing while the flake-like large debris was formed due to the initiation and propagation of microcracks during fracturing. The major defects in the microstructures gave different wear debris. Fine particle formation was promoted by discontinuities whereas flake debris was mainly due to the intersplat pores between splats and vertical cracks in the splat.
崔韓新,尹秉鉉,金亨駿,金宰喆,李昌禧 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.1
The isothermal oxidation behaviors of plasma sprayed NiCrAlY bond coatings (Ni22Cr10Al1Y and Ni31Cr11Al 0.6Y) were evaluated. Two unique microstructures such as oxide stringers and improperly flattened zones can be observed in the atmospheric plasma sprayed bond coatings. Structure and chemical composition of oxide stringer were examined by TEM and EDS. Improperly flattened zones had a high density of open porosities. These features affected the oxidation behaviors at both transient and steady state stages. At transient'oxidation stage, NiO, Cr_2O_3 and α-Al_2O_3 were observed on the surface simultaneously. Oxide stringers and improperly flattened zones had an especially high density of NiO and Cr_2O_3, which implied that these regions had inherently lower contents of Al. During steady-state oxidation, continuous α-Al_2O_3 reduced the diffusion rate of oxygen and thus rate of isothermal oxidation became slow. As the oxidation times increased, depletion of Al, the formation of NiAl_2O_4 layer and the formation of Cr_2O_3 occurred subsequently. And the hemispherical protrusions were also detected on the surface at room temperature. These protrusions were examined carefully.