JPS5928958B2 - High-temperature structures and high-temperature heating elements made of Ta, Nb and alloys of these metals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a hydrogen absorption prevention layer coated with W, Mo, Re, and alloys containing these metals as main components.
and high-temperature structures and high-temperature heating elements for use in vacuum or inert gas made of alloys of these metals.

Ta, Nb and their alloys are 1) Structures requiring high temperature strength Ii) High temperature heating element It is a useful metal material.

These materials have high purity (few impurities) and are mostly used in high vacuum or high purity inert gas atmospheres. Therefore, as long as these extremely active metal materials are used in the above-mentioned environment, their quality can be maintained and they can be used for a long period of time. When the pressure of active gases (such as oxygen, nitrogen, and hydrogen) in the atmosphere increases during use at high temperatures, these gases are absorbed and the material deteriorates. When Ta, Nb and their alloys react with oxygen and nitrogen, they become hard and their ductility decreases.

Therefore, when used in equipment used at high temperatures, the material may break due to the inability to withstand the tensile stress, compressive stress, and deflection that occur with thermal expansion. Also, when it reacts with hydrogen, its tensile strength, yield strength, and elongation decrease, making it brittle. Therefore, during use, cracks may occur in the material due to shocks and vibrations generated from the outside or from fluids.
As can be seen from FIG. 1, it is clear that the amount of oxygen absorbed into Ta increases as the oxygen partial pressure and temperature rise.

It is also clear from FIG. 2 that the elongation rate decreases as the amount of oxygen absorbed in Ta increases.

Further, FIG. 3 shows that Ta hardens as the content (absorbed amount) of oxygen and nitrogen increases. T
Examples of the use of a, Nb, and alloys of these metals as nuclear reactor materials are shown in the table below.

When used as a reactor material as described above, active gases such as oxygen and nitrogen must be prepared by: 1) manufacturing the equipment structure in a sealed manner;
11) By thoroughly degassing and removing residual gases before starting equipment operation, and faithfully operating according to regulations, these active gases can be reduced to considerably low levels. It is possible to keep the time.

However, even if the above measures are taken, hydrogen gas
It is recognized that this phenomenon occurs continuously during operation. The reason for this is due to structural materials (non-rust steel, nickel-based alloys, iron-based alloys, etc.) adjacent to high-vortex Ta, Nb, etc. and high-temperature Ta.
, Nb, and the like (e.g. heating element electrode copper, stainless steel, heat insulating material) are heated to a high temperature, hydrogen gas contained in these structural materials is released and permeated. V such as Ta, Nb, (the same is true for V)
Group A metals absorb hydrogen very easily, whereas MO,
It is known that Group VIa metals such as W hardly absorb hydrogen.

For example, Figure 4 shows the rate of hydrogen absorption into MO.High-temperature structures and high-temperature heating elements such as Ta and Nb are often used in the temperature range of 10,000 to 1,200℃. In that case, the absorption rate of hydrogen into MO is 0.01 atomic % or less. The welding force is difficult to process, and when welding, the welded part becomes brittle and Ta, Nb
cannot be processed into any shape.

In addition, the brittle-ductile transition temperature is high (MO is 20℃, W is 3
00°C), which has the disadvantage of being destroyed during use. Ta,Nb
High-temperature structural materials made from hexagrams and alloys of these metals, as well as when attaching or coating the surfaces of hexagrams and high-temperature heating elements with MO, Wf) films of the same high-melting point metals, are expected to be used as nuclear reactor materials. It is effective in preventing the absorption of hydrogen gas in the atmosphere and the resulting deterioration of materials.

Practical implementation methods include physical methods such as ion blasting, sputtering, etc., or chemical methods for high-temperature structures made of Ta, Nb, and alloys of these metals, and high-temperature heating elements that require prevention of hydrogen absorption.・10 to 10 of MO or W by chemical methods such as vapor deposition
It is sufficient to deposit a thickness of 0μ.

The embodiments of the present invention can be summarized as follows.

The surface of a high-temperature structure or high-temperature heating element made of Ta, Nb or an alloy of these metals is coated using a chemical coating method such as ion brazing or sputtering, or a chemical coating method such as chemical or vapor deposition. A method of coating with an alloy film containing MO, W, Re, or an alloy thereof as a main component.

[Brief explanation of drawings]

FIG. 1 shows the oxygen partial pressure, the amount of oxygen absorbed into Ta, and the oxygen absorption rate when Ta is heated at a high temperature.

Claims (1)

[Claims] 1. A hydrogen absorption prevention film (or layer) coated with W, Mo, Re, or an alloy containing these metals as main components is applied to the surface of a high-temperature structure and a high-temperature heating element made of Ta, Nb, and alloys of these metals. A high-temperature structure and a high-temperature heating element for use in vacuum or inert gas, which are made of Ta, Nb, and alloys of these metals.