• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.663-664
• /
• 2006

Sintered Ti(C,N)-based cermets were treated with hot isostatic pressing (HIP) at different nitrogen pressures. The tribological properties of the treated cermets have been evaluated. The results show that a hard near-surface area rich in TiN formed after HIP treatment. The cermets treated at higher pressure had a relatively lower friction coefficient and specific wear rate. In all cases the microhardness of treated cermets is higher than that without HIP natridation. The wear mechanisms of cermets were hard particle flaking-off and ploughing. It was also found that the HIP natridation is well-suited for improving the tribological properties of cermets.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 추계학술대회 논문집
• /
• pp.66-69
• /
• 2000

In order to analyze the densification behaviour of stainless steel powder compacts during hot isostatic pressing (HIP) at elevated temperatures, a power-law creep constitutive model based on the plastic deformation theory for porous materials was applied to the densification. Various densification mechanisms including interparticle boundary diffusion, grain boundary diffusion and lattice diffusion mechanisms were incorporated in the constitutive model, as well. The power-law creep model in conjunction with various diffusion models was applied to the HIP process of 316L stainless steel powder compacts under 50 and 100 MPa at 1125 $!`\acute{\dot{E}}$. The results of the calculations were verified using literature data It could be found that the contribution of the diffusional mechanisms is not significant under the current process conditions.

• 한국재료학회지
• /
• 제11권9호
• /
• pp.745-750
• /
• 2001

Ni-33.3at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ni and Si) were observed for the 15 min mechanically alloyed (MA 15 min) powder. but $Ni_2$Si and elemental phases were observed to coexist for the 30 min mechanically alloyed (MA 30 min) powder. Elemental Ni and $Ni_2$Si phases were observed for the HIPed compact of MA 15 min powder at 100 and 150 MPa for 2 hr at $800^{\circ}C$. Only the $Ni_2$Si phase was, however, observed for the HIPed compacts of MA 30 min powder. For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at $1100^{\circ}C$ at 150MPa for 2hr. The hardness values of the HIPed $Ni_2$Si compacts at $1100^{\circ}C$ at 100/150 MPa for 2 hr were higher than HRC 66. The densification and mechanical property of HIPed $Ni_2$Si compacts were found to depend on more HIP temperature than HIP pressure.

• 한국분말재료학회지
• /
• 제8권4호
• /
• pp.223-230
• /
• 2001

Ti-37.5at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ti and Si) were observed for the 5 min mechanically alloyed (MA 5 min) powder, but only $Ti_5Si_3$phase was observed for the 30 min mechanically alloyed (MA 30 min) powder. $Ti_5Si_3$phase was observed for the HIPed compact of MA 5 min and 30 min powders at 150 and 190 MPa for 3 hr at $1000^{\circ}C$. For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at $1350^{\circ}C$ at 190MPa for 3hr. The hardness values of the HIPed $Ti_5Si_3$compacts at $1350^{\circ}C$ at 150/190 MPa for 3hr were higher than HRC 76. The densification and mechanical property of HIPed $Ti_5Si_3$compacts was found to depend on more HIP temperature than HIP pressure.

• 한국재료학회지
• /
• 제10권2호
• /
• pp.128-137
• /
• 2000

가스터빈 블레이드 재료로 사용되는 IN738LC 니켈기 초합금 주조재에 대하여 고온등압압축(HIP) 공정에 의한 미세조직 변화와 고온 피로수명에 미치는 영향을 조사하였다. 세부적으로 HIP 처리에 따른 주조결함 제거와 피로변형 열화재의 물성재생효과 확인에 중점을 두었으며, 이를 위하여 회전굽힘 피로시험을 실시하고 변형전후의 미세조직을 광학 및 주사전자현미경으로 관찰하였다. HIP 처리 전후의 미세조직과 피로수명을 비교, 평가한 결과, 주조재와 열처리재의 피로수명 차는 크지 않았으나 HIP 처리재의 피로수명은 이들과 비교하여 평균 60배 이상 증가한 것으로 나타났다. 또한 인위적으로 고온 피로변형을 가한 열화재를 대상으로 반복 HIP 처리한 결과, 열화 변형조직이 신재 상태로 거의 완전히 재생될 뿐만 아니라, 재료내에 미세하게 잔존하던 주조결함까지 부가적으로 제거됨에 따라 반복 HIP 처리에 의한 피로수명 연장 효과가 크게 나타났다.

• 열처리공학회지
• /
• 제36권4호
• /
• pp.215-222
• /
• 2023

3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals, 3Y-TZP) ceramics are emerging as dental implant materials due to their superior optical and mechanical properties as well as excellent biophysical properties, in spite of low bioactivity. In this study, we investigated to sintered properties and microstructural defects of dental zirconia implants fabricated by ceramic injection molding and post-HIP (Hot isostatic pressing) processing and analyzed the processing parameters related with the obtainment of its high sinterd density. Sintered and microstructural parameters, i.e, apparent density, grain size and phase composition of zirconia implants fabricated by injection molding were dependent on the fixtute size and implant type. Maximum sintered density of 99.2% and minimum grain size of 0.3-0.4 ㎛ were obtained from large-scaled 2-body sample. In 1-body ceramic implant, high sintered density of 99.5% was obtained, but it had a little monoclinic phase and wide grain size distribution.

• 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.

• 대한기계학회논문집A
• /
• 제26권3호
• /
• pp.461-470
• /
• 2002

The present paper investigates the effect of hot isostatic pressing (HIPing) on mechanical properties, e.g., tensile strength, ductility and impact absorption energy of sand and die casted aluminum alloys. After HIPing at various temperatures and pressure conditions, uniaxial tensile test and Izod impact test of the samples were carried out. The experimental results showed improvements in uniaxial tensile strength, elongation and Izod impact toughness of sand casted aluminum alloy, while deterioration of a tensile strength fur die casted aluminum alloy. The effect of HIPing for microstructure of the cast aluminum alloy was also investigated.

• 대한기계학회논문집A
• /
• 제34권4호
• /
• pp.407-412
• /
• 2010

새로운 티타늄기 MMCs(W/ Ti-6Al-4V)에 대한 기계적 특성에 대한 연구를 행하여 평가한 결과를 나타내었다. HIP(hot isostatic pressing) 제조법과 RS(Rotary Swaging) 2 차 가공을 통하여 텅스텐 섬유 함유율이 각각 6, 9, 12 vol%인 W/Ti-6Al-4V MMCs 를 제작하였으며, 경도는 기존의 Ti-6Al-4V 합금과 비교하여 20-30%, 인장강도는 50%(비강도-38%) 높은 값을 얻었다. 섬유 함유율 9vol.% 에서 가장 높은 인장 값을 나타내었으며, MMCs 에서 메트릭스와 계면 사이에 생성된 확산상에 의해서 경도 및 인장강도가 향상되었다. 또한 피로 강도를 향상 시키기 위한 방법으로 메트릭스의 질적 향상을 위한 HIP 제작조건에 대한 추가적인 연구가 필요하다.

• 한국주조공학회지
• /
• 제43권3호
• /
• pp.175-181
• /
• 2023