타이타늄 합금에 플라즈마 이온 확산 방법으로 형성된 TiCN 박막층의 특성 = Characteristics of TiCN layer formed on Ti alloys by Plasma ion diffusion process

국문 초록 (Abstract)

본 연구에서는 CP-Ti, Ti-6Al-4V 합금, Ti-10Ta-10Nb 합금에 C와 N을 포함하는 플라즈마를 반응시켜 탄질화층(TiCN) 박막 증착을 하였다. 공정 변수로는 탄질화 공정온도는 750℃, 800℃, 850℃로 하였으며 공정압력 1.0Torr, 알곤 : 질소 : 메탄가스 유량비를 6 : 13 : 1, pulse power 2.3Kw로 고정시키고 실험을 실시하여 탄질화를 하였으며, 탄질화공정 온도변수가 탄질화층의 특성에 미치는 영향에 관한 연구.

다국어 초록 (Multilingual Abstract)

To improve the wear resistance of titanium alloys, many scientists have been focusing on the surface treatment studies. One of the surface treatment methods is the penetration of nitrogen and carbon into titanium alloys to form intermetallic film on it using plasma ion diffusion processing, but it is not generally used method yet. The advantage of plasma ion diffusion processing is that it can overcome the impediment of the carbon and nitride infiltration through the ion etching of titanium oxide film, and then the surface of host material is carbonitrided.
In this study, three treatment temperatures as 750, 800, and 850 ℃ were main experimental variables and then the specimens were subjected to analyse the microstructure and mechanical properties of carbonitrided titanium alloys. The plasma ion diffusion processing time was 1,080 min and the gas mixture of 93% N₂and 7% CH₄was used. The gas mixture ratio was confirmed at preliminary study. The characteristics of carbonitrided layer had been investigated using SEM micrograph, X-ray diffraction, EDS chemical analysis, microhardness measurements and wear test.
At the result of SEM micrograph, the thickness of the carbonitrided layer was continuously increased as the treatment temperature increase. TiCN, Ti₂N and Ti phases were detected by X-ray diffraction and TiCN layers has preferred orientation of (200) which was become clearer with increased treatment temperature.
The measured surface hardness values of the TiCN layer show a maximum of 1764HV_(0.02)in the case of the CP-Ti sample treated at 85 0℃. The microhardness was increased with layer thickness of TiCN+Ti₂N in the same matrix and the highest microhardness was obserued at the specimen which was treated at 850℃.
The result of depth measurement on wear track after the pin-on-disc wear test showed that the wear resistance was increased dramatically by plasma ion diffusion carbonitriding treatment, and the highest wear resistance was resulted a specimen which was treated at 850℃.
TiCN films formed at surface of all specimens by plasma ion diffusion of C and N. However the measured hardness value and wear resistance of alloys was different. Those properties straggly depend on the thickness of TiCN layer and also diffused later which was formed at beneath of TiCN layer.
Thicker TiCN and thicker diffused layer resulted in higher hardness and wear resistance.
Wearing was occurred by microploughing. The specimen which has higher hardness showed higher wear resistance because of restricted microploughing.

목차 (Table of Contents)

• 1. 서론 = 1
• 2. 이론적 배경 = 3
• 2.1. TiCN 박막의 형성방법 = 3
• 2.2. TiCN의 결정구조 및 물리적 기계적 성질 = 6
• 2.3. 타이타늄의 특성 = 8
• 2.4. 플라즈마 탄질화의 원리 = 9
• 2.5. 마모(wear) = 10
• 2.5.1. 내마모성에 미치는 인자 = 10
• 2.5.2. 마모형태 = 11
• 2.5.3. 일반적인 마모기구 = 12
• 3. 실험 방법 = 13
• 3.1. 시료의 준비 = 13
• 3.2. 티타늄의 탄질화처리방법 및 공정 조건 = 15
• 3.2.1. 실험장치 = 15
• 3.2.2. 전처리 = 17
• 3.2.3. 이온세정 및 초기 스퍼터 = 17
• 3.2.4. 탄질화처리 = 17
• 3.3. XRD 분석 시험 = 19
• 3.4. 주사전자현미경 관찰 분석 시험 = 20
• 3.5. EDS 정량분석 시험 = 20
• 3.6. Micro vickers 경도 분석 시험 = 21
• 3.7. 내마모성 시험 = 21
• 4. 실험 결과 및 고찰 = 23
• 4.1. XRD에 의한 탄화물 상분석 = 23
• 4.2. 탄질화층의 주사전자현미경 관찰 분석 = 27
• 4.3. EDX 분석 = 31
• 4.4. 탄질화층의 경도 및 탄질화 깊이에 따른 경도 분포 = 34
• 4.5. 탄질화에 따른 내마모특성 변화 = 37
• 5. 결론 = 51
• 6. 참고 문헌 = 53
• 영문초록 = 55