고온 환경에서 Cermet 코팅의 내열성 및 내마모성 특성에 관한 연구

다국어 초록 (Multilingual Abstract)

Hot-work tool steel(SKD61) is widely used in die-casting and hot-forming processes; however, severe surface degradation such as softening, wear, and aluminum adhesion frequently occurs under high-temperature and high-friction conditions, leading to reduced tool life. Although WC-based cermet coatings have been extensively applied using various coating techniques, conventional processes exhibit limitations in metallurgical bonding strength, local repairability, and geometric flexibility, motivating the application of Directed Energy Deposition (DED) as a surface strengthening approach. In this study, a WC10%–Ni60AA cermet coating was fabricated on SKD61 using the DED process, and its surface performance under high-temperature frictional environments was systematically investigated with emphasis on friction-driven thermal and mechanical interactions. The effects of process parameters and substrate preheating on deposition stability and microstructural evolution were examined, confirming that a dense and stable cermet microstructure could be obtained without excessive decomposition of WC reinforcements, while the non-preheated condition produced a fine eutectic structure resulting in the highest hardness. The deposited cermet coating exhibited significantly higher hardness than SKD61 and maintained superior mechanical stability up to 800 ℃. Thermal conductivity measurements revealed that the cermet coating consistently showed lower thermal conductivity than SKD61, influencing heat accumulation behavior under frictional loading. High-load wear tests demonstrated that the cermet coating achieved a lower and more stable coefficient of friction with substantially reduced wear loss compared to SKD61. In addition, high-speed friction tests against aluminum showed that the cermet coating effectively suppressed aluminum adhesion and exhibited the lowest surface temperature rise despite its low thermal conductivity, indicating that frictional heat generation rather than heat dissipation dominated the surface temperature response. These results indicate that the as-built cermet coating controls friction-induced thermal damage through an integrated microstructure–friction–heat interaction mechanism, providing a process-oriented strategy for applying DED-based cermet coatings to high-temperature tooling and friction-critical industrial components. KEY WORDS : Directed energy deposition, Cermet, Microhardness, Wear resistance, Thermal resistance

목차 (Table of Contents)

• List of Tables·ⅲ
• List of Figuresⅳ
• Abstract·ⅶ
• 1. 서론·1
• 1.1 연구 배경1
• 1.2 국내·외 연구 동향 5
• 1.3 연구 목적7
• 2. Cermet 적층 특성 분석을 위한 기초 실험10
• 2.1 직접에너지적층 공정·10
• 2.2 실험 장비 및 재료12
• 2.3 Cermet 적층 조건 설정을 위한 기초 실험15
• 2.3.1 직접에너지적층 공정 변수에 따른 단일 트랙 적층 특성 15
• 2.3.2 예열 조건 및 적층 레이어 수에 따른 cermet 적층 특성 23
• 3. Cermet 코팅층의 기초 물성 평가·25
• 3.1 미세구조 분석·25
• 3.1.1 XRD 분석 25
• 3.1.2 SEM 및 EBSD 분석 27
• 3.2 경도 특성 분석 31
• 3.2.1 로크웰 경도 시험·31
• 3.2.2 비커스 경도 시험·33
• 4. Cermet 코팅층의 내열성 평가·35
• 4.1 열전도도 특성 분석 36
• 4.1.1 실험 조건 및 방법36
• 4.1.2 실험 결과 및 분석38
• 4.2 고온 경도 특성 분석·41
• 4.2.1 실험 조건 및 방법41
• 4.2.2 온도별 경도 변화 분석 43
• 5. Cermet 코팅층의 내마모성 평가46
• 5.1 고하중 마모 시험47
• 5.1.1 실험 조건 및 방법47
• 5.1.2 실험 결과 및 분석49
• 5.2 고속 마모 시험 57
• 5.2.1 실험 조건 및 방법57
• 5.2.2 실험 결과 및 분석59
• 6. 결론66
• 참 고 문 헌70