• 제목/요약/키워드: Stellite 12 alloy-powder

검색결과 3건 처리시간 0.018초

PTA법에 의한 스텔라이트 12 합금 육성층의 조직과 경도에 미치는 전류와 예열온도의 영향 (The Effect of Current and Preheat Temperature on Structure and Hardness of Stellite 12 Alloy Overlayer by PTA Process)

  • 정병호;김무길;김규덕;김민영;이성열
    • 열처리공학회지
    • /
    • 제13권4호
    • /
    • pp.246-252
    • /
    • 2000
  • Stellite 12 alloy-powder was overlaid on 410 stainless steel valve seat using plasma transferred arc(PTA) process. Variation of characteristic of microstructure and hardness of deposit with current(90~150 A) and preheat temperature(R.T.~$400^{\circ}C$) was investigated. Important conclusion obtained are as follows; All welding conditions used produced a sound deposit layer with no defect in single pass welding. The maximum deposit had 4.0~4.8 mm in thickness and its bead width was increased with increase of current and preheat temperature. The deposit showed hypoeutectic microstruture, which was consisting of primary cobalt dendrite and networked $M_7C_3$ type eutectic carbides. The amount of eutectic carbides was decreased and its dendritic secondary arm spacing was increased with increase of current. Hardness of the deposit was decreased with increase of current. Preheat temperature up to $400^{\circ}C$, however, showed little influence on the hardness and microstructure. The hardness was also influenced by diluted Fe content near the interface in addition to microstructure and dendritic secondary arm spacing. Hot hardness at $500^{\circ}C$ showed higher than 300 HV.

  • PDF

DED 적층 제조된 Stellite 6 조성합금의 열간등방압성형 후처리 (Effect of Hot Isostatic Pressing on the Stellite 6 Alloy prepared by Directed Energy Deposition)

  • 서주원;고재현;천영범;김영도;장진성;강석훈;한흥남
    • 한국분말재료학회지
    • /
    • 제31권2호
    • /
    • pp.152-162
    • /
    • 2024
  • The directed energy deposited (DED) alloys show higher hardness values than the welded alloys due to the finer microstructure following the high cooling rate. However, defects such as microcracks, pores, and the residual stress are remained within the DED alloy. These defects deteriorate the wear behavior so post-processing such as heat treatment and hot isostatic pressing (HIP) are applied to DED alloys to reduce the defects. HIP was chosen in this study because the high pressure and temperature uniformly reduced the defects. The HIP is processed at 1150℃ under 100 MPa for 4 hours. After HIP, microcracks are disappeared and porosity is reduced by 86.9%. Carbides are spherodized due to the interdiffusion of Cr and C between the dendrite and interdendrite region. After HIP, the nanohardness (GPa) of carbides increased from 11.1 to 12, and the Co matrix decreased from 8.8 to 7.9. Vickers hardness (HV) decreased by 18.9 % after HIP. The dislocation density (10-2/m2) decreased from 7.34 to 0.34 and the residual stress (MPa) changed from tensile 79 to a compressive -246 by HIP. This study indicates that HIP is effective in reducing defects, and the HIP DED Stellite 6 exhibits a higher HV than welded Stellite 6.

스텔라이트 합금 용사 코팅의 피로 강도에 미치는 후열처리의 영향 (Effect of Post-heat Treatment on Fatigue Strength of Thermally-Sprayed Stellite Alloy on Steel)

  • 오정석;;이창규
    • 한국분말재료학회지
    • /
    • 제12권2호
    • /
    • pp.106-111
    • /
    • 2005
  • The effect of post-heat treatment on the coating characteristics and the fatigue strength of the gas flame thermally sprayed Stellite alloy coatings on $0.35\%$ carbon steel were investigated. The fatigue fracture surfaces of the heat treated samples were observed using SEM (Scanning Electron Microscopy). For as-sprayed samples, there was considerable scattering in the fatigue life due to the presence of the pores in the coating. After the post-heat treatment to improve the microstructural characteristics of the coating layer, the fatigue strength of the specimens was greatly improved, increasing with increasing the coating thickness. For the specimens with the 0.3mm and 0.5mm thick coating, the fatigue cracks originated in the substrate region just below the interface. On the contrary, for the specimens with the 1.0mm thick coating, they nucleated at the pore within the coating, and the fatigue strength was 2.6 times higher than that of the substrate due to the high fatigue resistance of the coating.