Alloys or metallic compositions – Ferrous – Nine percent or more chromium containing
Patent
1997-02-14
1998-09-01
Yee, Deborah
Alloys or metallic compositions
Ferrous
Nine percent or more chromium containing
420583, C22C 3822, C22C 3000
Patent
active
058001522
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates directly to metallic materials whereof the coefficient of thermal expansion is approximated to that of stabilized zirconia. More specifically, the present invention, by forming an alloy comprising either of a Cr-W-M-Fe system or a Cr-W-M-B-Fe system, where M can be one or more than two elements of an alloy element group comprising of Y, Hf, Ce, La, Nd or Dy, relates to oxidation-resistant metallic materials exhibiting excellent oxidation resistance at elevated temperatures and having an equivalent coefficient of thermal expansion to that of stabilized zirconia. The oxidation-resistant metallic materials are appropriate for an intermediate layer between the matrix substrate and stabilized zirconia serving as a heat-resistant and corrosion-resistant coating and solid state electrolyte for the solid oxide fuel cell which has been developed as a third generation fuel cell.
BACKGROUND OF THE INVENTION
Recently, energy conservation and global environmental problems have been crucial issues. Accordingly, various high temperature operating plant equipment including a gas turbine used for power generation have a tendency to require higher temperature and higher pressure operation. Because of the current industrial demands as mentioned above, the damage and deterioration of metallic materials being operated under critical operational conditions have become to be a serious technical problem.
As a result, in the current type of gas turbines for both aircraft and land power generators, it is a commonly adapted practice to apply a corrosion-resistant coating to the high strength superalloys for rotor blades and stationary blades as well. However, the problems associated with damage and/or deterioration problems due to high temperature corrosion remain for such coatings.
The principle and basic structure of the coating will be briefly explained by taking the thermal barrier coating (TBC) as an example. FIG. 1 is a schematic diagram showing the temperature gradients being developed entirely through the TBC structure, where A represents a ceramic layer, B is an intermediate layer, C is an alloy, and Tg indicates the high temperature combustion gas temperature, while Ta refers to a cooling-air temperature and temperatures T.sub.1, T.sub.2, T.sub.3, T.sub.4, T.sub.5, and T.sub.6 indicate respective temperatures at surface or interface zone. FIG. 2 depicts a cross sectional view of TBC when applied to the combustion equipment.
The main function of TBC is to prevent a temperature raise in the surface areas of metallic components by coating a ceramic material having lower thermal conductivity onto metallic components exhibiting the temperature gradient, as seen in FIG. 1. Application of the TBC to the gas turbine system, particularly for combustion devices, has been done for more than 10 years. Recently, application of the TBC to the cooling blades has become a more frequent practice. According to the tests using actual blade, it was recognized that the TBC system exhibited a thermal barrier effect ranging in temperature from 50.degree. to 100.degree. C.
TBC normally comprises a ceramic fusion spray layer and an intermediate fusion spray layer, wherein the former consists mainly of ZrO.sub.2 (a solid solution with a stabilizing component such as MgO, Y.sub.2 O.sub.3, or CaO) having much lower thermal conductivity of 0.005.about.0.006 cal/cm.s..degree.C. than Al.sub.2 O.sub.3 (0.04.about.0.08 cal/cm.s..degree.C.) or TiO.sub.2 (0.01.about.0.02 cal/cm.s..degree.C.), while the latter intermediate layer comprises of a Ni-Al alloy, Ni-Cr alloy or M-Cr-Al-Y alloy (where M can be Fe, Ni, Co or the like) in order to relieve the thermal expansion difference between the alloy (base) material and thereof, and to enhance the corrosion resistance. Research has been conducted to form a multi-layer structure in which the intermediate layer is formed as a mixed layer of metal and ceramic materials, or to construct the layer having a completely gradient composition.
As a fuel cell is consi
REFERENCES:
patent: 2553330 (1951-05-01), Post et al.
patent: 5154885 (1992-10-01), Czech et al.
Taimatu Hitoshi
Ueda Masami
Sumitomo Special Metals Company Limited
Yee Deborah
LandOfFree
Oxidation resistant metallic materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oxidation resistant metallic materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oxidation resistant metallic materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-262780