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The characteristic of interface layer and the effect of bias voltage on the microstructure of c-BN films were studied in the microwave plasma hot filament C.V.D process. c-BN films were deposited on a high speed steel(SKH-51) substrate by hot filament CVD technique assisted with a microwave plasma to develop a high performance of resistance coating tool. c-BN films were obtained at a gas pressure of 20 Torr, vias voltage of 300 V and substrate temperature of 800°C in B₂H₆-NH₃-H₂ gas system. It was found that a thin layer of hexagonal boron nitride(h-BN) phase exists at the interface between c-BN layer and substrate.
Nanosize tungsten powder was synthesized by ultrasonic spray pyrolysis method through a solution containing ammonium metatungstate hydrate [(NH₄)₆W₁₂O₃₉ㆍH₂O] and reduction treatment. It was expected the improvement of mechanical properties due to increasing surface free energy and surface activity. Starting solutions with each concentration, reaction temperature and reduction treatment were significantly influenced on the formation of tungsten size and phase. It was found that particle size was decreased with concentration of starting solution and surface tension were decreased. The particle size was increased at thermal decomposition temperature above 600℃ by neck growth of interparticles. Tungsten particles were formed by reduction reaction in atmosphere of hydrogen gas at the temperature above 700℃.
The effect of Ti additions to molten borax have studied on the growth of intermetallic phase formed during electro-boronizing of the carbon steel and STS 430. The thickness of alloy layer was measured by an optical microscope and the structure was identified by X-ray diffractometer. The penetrated depth of the boron increased with addition of Ti but decreased above certain amount. The hardness and sliding wear resistance of carbon steel and STS 430 which penetrated deeply the diffused depth the boron as raising temperature and current density increased more remarkable than other surface treatment.
열평형에 가까운 상태인 Hot-Filament assisted C.V.D 장치를 이용하여, 저압 기상 하에서 diamond 박막을 생성시킬 때 온도, 압력, sources gas, substrate의 종류, 과포화 및 atomic hydrogen의 영향 등을 핵생성과 성장에 관련하여 증착층의 성질을 조사하였다. CH_4-H_2 system에서 CH_4/H_4 분율이 1% 이하일 때 다이아몬드 결정상이 나타났고, 전처리로 substrate 표면을 다이아몬드 분말로 연마한 것이 초기단계에서 현저하게 핵생성과 성장을 촉진하였다. We have investigated the effect of hydrocarbon deposition on nucleation and growth of Diamond crystal from CH_4/H_2 in Hot filament C.V.D. Well faceted diamond crystallization is produced at low pressure (20∼50 Torr) and low concentration (1% CH_4./H_2 mole fraction). Co-deposition of non diamond carbon has to be suppressed by atomic hydrogen expressively presents in reaction chamber.
To study the effect of silicon additions on the boronized depth, hardness and wear of the boronized layer, an electro-boronizing on the substrate such as electrolytic iron, ferritic and austenitic stainless steel has been carried out at the current density of 0.5A/㎠ and in the temperature range of 800-1000℃ for 1-5 hours. the findings from the experiment are summarized as follows. 1) Increased boronize depth was obtained with increased addition of silicon. excess silicon addition, however, inhibited the buronizing due to the increased viscosity of electrolyte. 2) Deeper boronized layer was resulted with ferritic than austenitic stainless steel. the boronized depth of the both stainless steels, however, were only one-third that of the electrolytic iron. 3) Wear resistance of the substrates was improved markedly by boronizing, showing the best result in the ferritic followed by austenitic stain-less steel and electrolytic iron.
TiAl 금속간화합물은 기존의 내열재료인 Ni기지 Superalloy에 비해 비강도가 크고 기계적성질이 우수한 데 상온에서의 낮은 인성과 제조시 Ti의 높은 활성으로 인하여 사용이 제한되어 왔다. 본 연구에서는 Plasma arc melting법으로 γ상영역의 조성인 Ti-48 at% Al합금을 제조하여 그 응고과정과 기계적성질을 조사하고 제3원소인 Mn을 첨가했을 때의 조직에 미치는 영향을 조사하여 다음과 같은 결론을 얻었다. 1) Ti-48.1 at% 합금의 응고조직은 층상조직의 결정립계에 γ상이 석출하는 α_2+γ의 2상조직이다. 2) Ti-48.1 at% 합금에 1.22 at% Mn을 첨가하면 주조상태에서 초정 α상 Dendrite 조직이 미세해지며 경도는 감소하는 것으로 나타났다. Ti-48.1 at% Al alloy and Ti-48.3 at% Al-1.22 at% Mn alloy in the composition range of γ phase were casted by using plasma arc melting system. Microstructure, mechanical properties and solidification process of TiAl alloys were investigated. Dendrite structure of primary α phase in alloy added 1.22 at% Mn to Ti-48.1 at% Al was fined and the amount of α_2 phase was decreased.