Metal treatment – Stock – Chromium – molybdenum – or tungsten base
Reexamination Certificate
2002-03-06
2004-02-17
King, Roy (Department: 1742)
Metal treatment
Stock
Chromium, molybdenum, or tungsten base
C420S428000
Reexamination Certificate
active
06692587
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a Cr-base heat resisting alloy. More particularly, this invention relates to a Cr-base heat resisting alloy with excellent high temperature strength and room temperature ductility, which can be used under a high temperature environment of 1100° C. or more and is hopeful for adapting to a material for stationary or moving blades of a gas turbine.
2. Description of the Prior Art
As a heat resisting material for structural purposes such as stationary or moving blades of a gas turbine, there has widely been used Ni-base alloys or Co-base alloys. However, these alloys are relatively high in cost and their expiration temperature is restricted to around 1100° C. on account of a limitation in terms of their melting point, etc. Since thermal efficiency of a gas turbine is remarkably improved by raising a temperature at an inlet of the gas turbine, development of a heat resisting alloy for structural purpose that can be used at higher temperatures is demanded.
As one of the materials that is the most excellent in high temperature strength and relatively low in cost, pure Cr is known. However, in the case where the amount of Cr is around 60 atomic %, conventional Cr and Cr-base alloys exhibit not only room temperature brittleness but also almost little ductility. Therefore, they cannot be processed after melting and solidification and are impossible to adapt to a material for structural purposes. A Fe—Cr base alloy that has an excellent balance of strength and ductility in a high temperature range of around 1000° C. is proposed. However, high temperature strength and ductility of the Fe—Cr base alloy are not satisfactory compared with those of a Ni-base alloy. In addition, ductility and high temperature strength of the Fe—Cr base alloy are seriously damaged by impurities and therefore, the total amount of impurities is suppressed to 60 mass ppm or less. The Fe—Cr base alloy cannot be made from raw materials containing impurities at a commercial level, but can be made from raw materials especially high in purity. Consequently, the Fe—Cr base alloy is high in cost and much care is needed during production.
SUMMARY OF THE INVENTION
This invention has an object to provide a Cr-base heat resisting alloy with excellent high temperature strength and room temperature ductility, which can be used under a high temperature environment of 1100° C. or more and is hopeful for adapting to a material for stationary or moving blades of a gas turbine.
According to an aspect of this invention, there is provided a Cr-base heat resisting alloy, which contains Cr as a main component element and at least one element selected from the group consisting of Re and W in amount of from 1 atomic % to 40 atomic %.
A 0.2% yield strength at 1200° C. of the Cr-base heat resisting alloy is 500 MPa or more.
The Cr-base heat resisting alloy is, for example, made by the following process:
Cr, Re and W that contain C, N, O and S as impurities, each of which contains such impurities in a total amount of 400 mass ppm or less, 1000 mass ppm or less, and 300 mass ppm or less, are used a raw material. A mixture of Cr and at least one element of Re and W in amount from 1 atomic % to 40 atomic % is made molten and solidified according to a usual manner.
That and other objects, features and advantages of the invention will become more apparent upon reading of the following detailed specification and drawing, in which:
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Bannai Eisuke
Harada Hiroshi
Kobayashi Toshiharu
Koizumi Yutaka
Ro Yoshikazu
King Roy
National Institute for Materials Science
Wenderoth , Lind & Ponack, L.L.P.
Wilkins, III Harry D.
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