http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
TiAl 의 내산화성 향상을 위한 확산코팅에 미치는 Nb 과 Cr 의 영향
김규영,정환교,오창혁 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.8
The effects of alloying elements in the TiAl₃ coating layer are studied with respect to mechanical property and oxidation resistance. All the TiAl alloys are pack aluminized in the same condition of high activity process. The mechanical property of TiAl₃ coating layer formed on the surface by pack aluminizing depends considerably on the third alloying element in the TiAl matrix. The TiAl₃ layer formed on the TiAl alloy becomes thicker and has the finer micostructure as the content of Nb or Cr is increased. Micnhardness test reveals that addition of alloying element of Nb or Cr improves the ductility of the coating layer and thus improves the cracking resistance. Cyclic oxidation test shows that the TiAl₃ coating layer formed on the TiAl alloy has a better oxidation resistance as the content of Nb is increased. The ductility and oxidation resistance of the TiAl₃ coating layers are increased by Nb addition, which contributes to the grain refinement of TiAl₃ structure.
Si 첨가가 Fe-14Cr-1A1 페라이트계 스테인리스 합금의 고온 내산화성에 미치는 영향
김규영,정환교,안장규 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.9
A study has been made to investigate the effects of silicon(Si) addition on the oxidation properties of Fe-14Cr-1Al ferritic stainless steels at 1173K. Four steels containing different amount of Si (0.5, 1, 2, 5 wt% Si) were arc melted and homogenized at 1473K for 24 hours and oxidized at 1173K. Both the isothermal and cyclic oxidation tests revealed that the addition of Si increased the oxidation resistance of Fe-14Cr-1Al alloy. With 0.5w%Si, Cr oxide was formed as surface oxide, and Si, Al oxides were formed internally below Cr oxide layer. With 1w%Si, Al oxide was mixed with Cr oxides on the surface. However, with Si content higher than 2w%, a stable Al₂O₃ layer was formed rapidly. From theoretical evaluation using ChemSage^(TM) program, the Al activity in Fe-Al-5Si steel is about 5 times higher than that in Fe-1Al alloy at 1173K, which is the most probable reason for the rapid formation of Al oxide in the high Si steels.
김규영,정환교,Stott, F . H . 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.6
The oxidation behavior of the iron aluminides and the alloy of the same kind containing zirconium in air at 1200℃ has been examined. The oxide formed on the zirconium free Fe₃Al is highly convoluted and consists of equiaxed grains. On the other hand, with addition of zirconium to the Fe₃A1, distinct changes occur in the oxide morphology. The oxide is less convoluted and consists of columnar grains. The main factor responsible for this change is the facts that addition of zirconium into the external oxide suppresses the diffusion of aluminum within the external oxide. Other secondary advantages resulting from the addition of zirconium in the Fe₃Al is the strengthening of the Fe₃Al. Convolution of oxide can be aided by a weak substrate and weaker alloys would be expected to have more convoluted scales upon exposure to an oxidizing environment at sufficiently high temperature.
TiAl 의 고온내산화성 향상을 위한 EB-PVD 방법을 이용한 Al+Y 혼합코팅
김규영,정환교,최태완 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.1
A method for "Al+Y codeposition" was developed to improve the resistance of high temperatrue oxidation of TiAl using a single process of EB-PVD. Isothermal and cyclic oxidation tests at 950℃ showed that the Al+Y codeposition improved the oxidation resistance of TiAl significantly. During oxidation, the oxides formed in the Al+y codeposition layer are composed of two parts ; the outer (Y,Al)O layer and the inner Al₂O₃, layers containing small amount of Y-rich oxide. Both the outer (Y,Al)O and inner Al₂O₃ layers have a fine-grained structure which prevents effectively inward diffusion of oxygen and consequently prohibits formation of porous TiO₂. During cyclic oxidation, these (Y,Al)O and Al₂O₃, layers relieve easily both the growth and thermal stresses by permitting easy plastic deformation. However, when exposed to high temperature for an extended period of time, an Al₂O₃, layer having a columnar structure is developed underneath the existing fine-grained Al₂O₃, layer by reaction with Al from the substrate TiAl. This columnar Al₂O₃, is responsible for degradation of the oxide layer.
이온플레이팅 방법으로 코팅된 이트륨이 Ni3Al 의 고온내산화성에 미치는 영향 (2)
김규영,정환교 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.8
The Y-coated Ni₃Al with post heat treatment shows much better oxidation resistance than the Y-coated Ni₃Al without post heat treatment. In order to explain the effect of post heat treatment at low oxygen pressure, post heat treatment after Y-ion plating is performed in flowing hydrogen as a function of time. During post heat treatment, the Y-coated layer is modified into (Y, Al)O-type oxide by reaction between Y₂O₃, and Al₂O₃. Thickness of the modified Y-layer is related to oxygen pressure and time. The Y-modified layer formed during post heat treatment acts as a barrier to the transport of oxygen. The fine (Y,Al)O-type oxide can relieve easily growth stress by permitting easy plastic deformation, and can absorb the thermal stress developed in the Al₂O₃ layer. The tensile stress generated by the difference in thermal expansion coefficient of the (Y,Al)O-type oxide and Al₂O₃, layer compensates the large compressive stress generated by the difference in thermal expansion coefficient of the Al₂O₃layer and Ni3Al alloy.
이온플레이팅 방법으로 코팅된 이트륨이 Ni3Al 의 고온내산화성에 미치는 영향 (1)
김규영,정환교 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.7
The yttrium (Y) coated Ni₃Al with post heat treatment has shown a good high temperature oxidation resistance. To understand the effect of Y-coating and post heat treatment on the oxidation resistance of Ni₃Al, the specimens were coated with Y by ion-plating method, and heat treatment was performed before or after Y-coating at low oxygen level. Performance of the Y-coated Ni₃Al was evaluated by isothermal and cyclic oxidation tests. A simple deposition of Y on Ni₃Al did not change the oxidation kinetics, but the post heat treatment after Y-ion plating decreased significantly the oxidation rate of Ni₃Al. The scale formed on the Y-coated Ni₃Al with post heat treatment after Y-ion plating showed a fine and dense structure which was grain refined by the presence of the (Y,Al)O-type oxide in the scale. The coated Y layer becomes a Y-Al compound after post heat treatment. The presence of (Y,Al)O-type oxide in grain boundaries of Al₂O₃ modifies the diffusion rates of Al and oxygen, and the oxide microstructure during oxidation. Improvement of cyclic oxidation resistance of Ni₃Al by the Y-coating is attributed to the fact that the finegrained oxides developed by the presence of (Y,Al)O-type oxide can easily relieve the growth stress.
제 3 원소의 첨가가 알루미나이드 코팅된 TiAl 합금의 고온내산화성에 미치는 영향
김규영,정환교,오창혁 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.8
The effects of third elements in the TiAl on the mechanical property and the oxidation resistance of aluminized coating layer formed on the TiAl have been studied. With the basic alloy of TiAl, the ternary alloys of TiAl-2 at%X were prepared X being Nb, Cr, Fe and V. All the specimens were pack aluminized in the same condition of high activity process. The toughness of the coating layer was evaluated by vicker's hardness test, and the oxidation resistance was evaluated by isothermal and cyclic oxidation tests. The third element added in the TiAl affected the property of the TiAl₃ coating layer. Among the alloying elements evaluated, Nb showed the moat positive effects on the coating thickness, coating microstructure, and toughness and stability of the coating layer. The oxidation resistance of aluminized TiAl alloy was influenced by the property of coating layer. The best oxidation resistance was obtained in the aluminized TiAl alloy with Nb which has most tough and thick coating layer. However, further studies are required to clarify the exact role of Nb on the mechanism of coating process and on the mechanical property of coating layer.