Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1998-11-20
2000-10-17
Speer, Timothy M.
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
428668, 428679, 428680, 428685, 428937, 427422, 427424, 427427, B32B 1500, B05D 102
Patent
active
061328901
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FILED
This invention relates to a high-temperature spray coated member having an excellent high-temperature oxidation resistance as a high-temperature member such as boiler, gas turbine, jet engine, diesel engine or the like and a method of producing the same.
BACKGROUND ART
As to a high power generator such as a boiler, a gas turbine, a jet engine, a diesel engine or the like, there are many studies for mainly improving a heat efficiency. However, the improvement of heat efficiency forces a severe thermal load to a constructional part (material). As a metal material used in a high temperature portion of the high power generator, therefore, it is required to have excellent high-temperature oxidation resistance and high-temperature corrosion resistance. Particularly, if it is intended to use a fuel containing impurities such as V, Na, S and the like, since inorganic compounds containing these impurities violently corrode and wear the metallic material at a high-temperature state, it is necessary to maintain the metallic material at a stable state for a long time under such an environment.
In order to satisfy such a requirement, there have been developed many heat resistant alloys consisting essentially of nonferrous metallic elements such as Cr, Ni, Mo, Co, W, Ta, Al, Ti and the like from the old time, which are called as so-called super-alloys.
In these heat resistant alloys, however, the high-temperature strength is most preferential, so that it tends to suppress an addition amount of a metal element not serving to the improvement of the strength as low as possible. A typical example of the metal element not serving to the improvement of the strength is Cr, Al, Si or the like, but these elements are excellent in the oxidation resistance and resistance to high-temperature corrosion. Therefore, it is ordinary that the super-alloy preferentially requiring the above high temperature strength is poor in the oxidation resistance and resistance to high-temperature corrosion.
Heretofore, a metal elements such as Cr, Al, Si or the like or an alloy thereof has previously been applied to a surface of a super-alloy member used under a high temperature environment through a spraying process, a diffusion treatment method or the like to compensate for the lowering of resistance force to chemical damage of the super-alloy.
In the spraying process, it is merit that the kind of the spraying material may optionally be selected, but there is a drawback that the resulting coating is porous and is poor in the corrosion resistance and adhesion property because the treatment is carried out in air.
In this connection, there has recently been developed a method wherein plasma spraying is carried out in an argon gas atmosphere of a low pressure containing substantially no air (oxygen) (low-pressure plasma spraying process), whereby drawbacks inherent to the atnospheric-sprayed coating have largely been improved, but it can not be said that such a coating is still sufficient under recent environment exposed at higher temperature.
On the other hand, the conventional diffusion treatment method is relatively easy when Cr, Al, Si and the like are treated individually, but it is hardly said that the oxidation resistance and the resistance to high-temperature corrosion are sufficient. And also, this treatment is required to be conducted at a higher temperature state of about 1000.degree. C., so that it has a drawback that mechanical properties of super-alloy matrix lower.
Under the above circumstances, JP-A-55-104471 proposes a method wherein Ni--Cr alloy as an oxidation-resistant metal is sprayed to conduct a diffusion treatment of Al, Cr or the like.
In this method, however, the treatment at high temperature can not be avoided, so that it is inevitable to lower the mechanical properties of the matrix though the adhesion property and denseness of the sprayed coating are improved.
On the other hand, the development of spraying materials is carried out for using under high-temperature environment. A typical material is a heat
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English Language Abstract of JP No. 3-207849.
English Language Abstract of JP No. 56-51567.
English Language Abstract of JP No. 55-104471.
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Harada Yoshio
Suizu Tatsuo
Teratani Takema
Speer Timothy M.
Tocalo Co., Ltd.
Young Bryant
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