티타늄 스크랩을 이용한 분말 제조 및 소결 성형체의 특성평가

Abstract

As the development of domestic industry, the demands for advanced and special metals have been increasing rapidly. Titanium (Ti) and its alloys are used in various fields such as the aerospace, chemical industry, marine and automobile industries. The specific gravity of titanium 4.51, copper or nickel of approximately 50%, 60% lighter than steel, but specific strength(Pure titanium 60~160kgf/mm2)is much higher than other structural materials, because weight of the infrastructure of lightweight there is a possibility of doing to from various industry. But high temperature reactivity-problem of the difficulty processing and it compares in the different structure material and there is a weak point which is a high price. Therefore, Ti powder was fabricated using Ti scarp by hydrogenation-dehydrogenation (HDH) method in this study. Ti compacts using the powder was manufactured by pressureless and spark plasm sintering, and then analyzed mechanical property, microstructure. for improving corrosion resistance, add Pd, fabricated Ti-Pd alloy poweder, by spark plasma sintering, manufactured compacts , analyzed corrosion resistance of pure Ti and Ti alloy. It was fabricated that Ti-Pd alloy powder added Pd for improving corrosion resistance and compacts was manufactured by SPS and analyzed corrosion resistance of pure Ti and Ti alloy. Results of this study are described as follows.

1. When treated Ti scrap with hydrogenation in hydrogen atmosphere, confirmed hydrogenation treatment with heat of reaction near at 350℃. Also, Ti powder was fabricated with dehydrogenation treatment at 750℃.

2. It was observed typical TiH2 and Ti peak at XRD analysis of fabricated Ti powder. But looked excessive oxygen content at fabricated Ti powder, so treated dehydrogenation using Ca for lower oxygen content. After dehydrogenation treatment, it was appeared to decrease a quarter than the first oxygen content of powder.

3. When compared mechanical characteristics and microstructure of Ti compact as oxygen content, oxygen content was little different in microstrcutre. But it appeared many diffrence in mechanical characteristics. The higher oxygen content, the higher was hardness but strength was lower.

4. When compared microstructrue and mechanical characteristics of Ti compact as sintering method using fabricated Ti powder. In case of fabricated compact that can sinter at relatively low-temperature by SPS, it was got very fine compact and grain growth was not occurred. But in time of compact that fabricated by pressureless sintering, it can be found surface porosity and grain growth. There is no difference between hardness and strength in mechanical characteristics. It is known that grain size has influence on mechanical characteristics at material. However, it was considered that oxygen content included Ti powder was more influenced mechanical characteristics of Ti than grain size in this study.

5. Corrosion resistance of compact added Pd was better than compact added pure Ti. When it added 2wt% Pd, corrosion resistance is very good. But corrosion rate was increased by passivity fracture.