Densification behavior and grain growth of tool steel powder compacts during pressureless sintering, sinter forging, and hot isostatic pressing were investigated. Experimental data were compared with results of finite element calculations by using the constitutive model of Abouaf and co-workers and that of McMeeking and co-workers. Densification and deformation of tool steel powder compacts were studied by implementing power-law creep, diffusional creep, and grain growth into the finite element analysis. The shape change of a powder compact in the container during hot isostatic pressing was also studied. The theoretical models did not agree well with experimental data in sinter forging, however, agreed well with experimental data in hot isostatic pressing.

The densification of the compacts of pure Co, Fe+50%.Co and Fe+25% Co sintered under H gas or in vacuum was investigated. The effects of AL, Nb, Ti, and V additions on the densification were also studied. The sintered compact of Co was fully-dense when the density of the compact was lower than . However, above , it was never fully-dense regardless of sintering atmosphere, temperature, and time. The densification of sintered compacts of Fe-50% Co and Fe-25% Co were always incomplete. While the addition of AL made all compacts fully-dense, the addition of Ti was effective for the compacts of Co and Fe-25% Co. V was effective only for the Fe-25% Co. These results tell us that the particle size of Co powder, the amount of Fe, and the amount of additives forming stable oxides play on important role for the complete densification. Therefore it is desirable to reduce or eliminate the equilibrium pressure of HO or CO in isolated pores to obtain a fully-dense sintered compact.

고출력 IC회로의 방열재료 및 전기접점재료로 이용되고 있는 W-Cu복합재료를 기계적합금화법으로 제조하였다. 기계적합금화한 분말을 300MPa로 폭 16mm, 높이 4mm의 원반형으로 제조하였다. 소결은 1200˚C에서 1400˚C까지 수소분위기에서 행하였다. 이렇게 제조된 시편의 절단된 면을 연마하여 SEM으로 관찰하였다. 균질한 W-Cu복합재료를 10시간 기계적합금화를 행한 후에 얻을 수 있었고, 1330˚C에서 1시간 소결한 시편의 경우 거의 99%에 가까운 치밀한 조직을 얻을 수 있었다. 또한 기계적합금화시간이 증가함에 따라서 Fe의 혼입은 직선적으로 증가하였으며, 이로 인한 금속간화합물상의 형성은 W입자 성장을 방해하고 경도를 증가시켰다.

The densification behavior during a sintering of M2 and T15 grade high speed steel powder compacts was reported. Sintered densities over 98% theoretical were achieved by a liquid phase sintering in vacuum for both grades. The optimum sintering temperature range where full densification could be achieved without excessive carbide coarsening and incipient melting was much narrower in M2 than in T15 grade. The sintering response was mainly affected by the type of carbides present. The primary carbides in M2 were identified as type whereas those in T15 were MC type which provides wider sintering range. The addition of elemental carbon up to 0.3% lowered the optimum sintering temperature for both grades, but had little effect on expanding the sintering range and sintered structure.

The effect of the role of alloyed components on the densification of two kind of high speed steel (mixed and prealloyed powder), which were sintered at 1403~ 1573 K for 7.2 ks in vacuum, was investigated. The results obtained were as follows. (1) Without the presence of Vanadium (V), the relative density of sintered compacts (Ds) could not reached the density of 100% regardless of the. elements in the compacts. (2) The addition of V up to 2 mass% did not result In the complete densification when the carbon content was fixed at 2% in the compact. (3) With the fixed amount of V of 7%, Ds decreased with the increase of the carbon content. (4) The addition of mixed fine powder to the prealloyed powder in the range of 20 to 40% provided the complete densification and carbide panicles of 1~2 through the solid phase sintering. (5) The V element played important role in controlling the complete or incomplete densification of the sintered compacts in the alloyed component because of its formation of stable oxide and carbide as well as the low equilibrium pressure of CO gas.

프로판(C3H8)을 반응가스로 사용하여 등온 저압화학기상침투법(low-pressure chemical vapor infiltration)으로 탄소/탄소 복합재료를 치밀화 할 때 반응온도, 반응가스농도, 가스유량, 반응압력 등의 제조공정변수들이 치밀화에 미치는 영향을 알아보기 위하여 실험계획법(Rdbust design method)에 의한 실험을 행하였다. 1회의 등온 저압화학기상침투 실험으로 탄소/탄소 복합재료의 부피 밀도와 표면과 내부의 부피 밀도의 차이를 특성치(characteristic value)로 한 실험계획법의 분산분석(analysis of variance)에 의하면 반응온도, 반응가스농도, 가스유량 등의 제고공정변수가 치밀화에 기여도가 높으며, 반응압력의 기여도와 제조공정변수들의 교호작용(interaction)에 의한 기여도는 낮은 것으로 나타났다. 반응온도가 1100˚C, 반응가스농도가 100% C3H8, 가스유량이 100 SCCM, 반응압력이 5torr인 조건에서 탄소/탄소 복합재료는 가장 높은 부피 밀도값을 나타내었으나 시편의 표면과 내부의 부피 밀도 차이값은 컸다.