JPS59211567A - Metallic member provided with sprayed alloy layer - Google Patents

Abstract

PURPOSE:To improve the resistance to high temp. particle erosion of a boiler tube, etc. by forming a sprayed alloy layer contg. a specific metallic carbide on the surface of the boiler tube, etc. CONSTITUTION:A boiler tube of a boiler using coal as fuel is subjected to the high temp. erosion damage by clinker of coal ash or a solid matter such as flyash or the like. An Ni base alloy or Co base alloy contg. 15-50% by volume % hard metallic carbide such as Cr3C2 or WC is sprayed thereon to 0.1-0.5mm. thickness in order to prevent such damage. A hard carbide such as Mo, Si, B, V or the like may be otherwise used in combination as desired. The sprayed layer having high resistance to the high temp. particle erosion is formed and the life of the boiler tube is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal component with a sprayed alloy layer, and in particular to a metal component with a thermal sprayed alloy layer that exhibits excellent resistance to hot particle erosion such as that found in coal-fired boilers.

High-temperature energy devices, such as fuel-fired boilers, fluidized bed reactors, coal gasification and liquefaction equipment, have traditionally relied primarily on petroleum, but today the need to use alternative energy has been recognized. As a result, coal use is on the rise.

However, the equipment design is based on the design concept when using oil, and the problems when using coal have not yet been fully resolved. For example, coal-fired boilers are manufactured using the same material composition as conventional oil-fired boilers. However, in coal-fired boilers, unlike oil-fired boilers, the solid ash inside the boiler becomes clinker and is suspended as i-fly ash, so the boiler tubes that make up the coal-fired boiler are Significant erosion damage occurs at high temperatures. Although these problems are recognized by those skilled in the art, the erosion behavior caused by high-temperature particles is not yet clear, and there are few material countermeasures. However, even with these design measures, when restricting the flow velocity etc., it is possible to create uneven flow areas where the specific flow velocity is higher than expected, or the need to install a protector. There have been reports of cases where the protector itself is damaged quickly and is rendered useless.

Incidentally, in the past, thermal spraying of nickel-based alloys or cobalt-based alloys has been practically used for wear resistance such as rubbing wear or corrosion resistance, but the above-mentioned □
There are no examples of it being used for high temperature particle erosion resistance. Note that rubbing wear usually occurs when objects make reciprocating or rotating contact, while erosion occurs when a solid collides with an object at high speed, causing thinning, and both mechanisms are Essentially different. Therefore, there is no phenomenological commonality or relationship between rubbing wear resistance and high-temperature particle erosion resistance (and there is no knowledge of high-temperature particle erosion resistance in the prior art).

As already mentioned, there are currently almost no material measures to prevent erosion damage caused by high-temperature particles, but if there were cost-effective measures, it would be possible to create leeway in the design of coal-fired boilers, such as those mentioned above. This has great effects, such as making it possible to determine the appropriate protector material.
If such material measures are taken, it will be possible to increase the average flow velocity, and the benefits of miniaturization of the device and improvement of thermal efficiency can also be expected.

It is therefore an object of the present invention to provide metal parts that do not exhibit superior resistance to erosion by hot particles as found in coal-fired boilers.

In addition, the erosion ffi damage in general high-temperature energy equipment mentioned above often occurs in areas where the flow velocity is locally high, such as in drifting areas, and local countermeasures are often required.
Accordingly, another object of the present invention is to provide a metal member that exhibits localized resistance to erosion by high temperature resistant particles from such a point of view.

Thus, the gist of the present invention is that Cr and/or
Or total carbide including W carbide in volume ratio of 15 to 50
A metal component with exceptional resistance to hot particle erosion with a thermally sprayed alloy layer containing %.

Here, by using metal members such as steel plates and steel pipes provided with the sprayed alloy layer according to the present invention, it is possible to prevent high-temperature erosion damage to such members. Traditionally, thermal spray alloys have not been used for such applications. Although the thermal spray alloy itself in the present invention is not particularly limited, in many cases heat resistance and corrosion resistance are also required, so generally a cobalt-based alloy or a nickel-based alloy will be used. The method is not particularly limited either, and thermal spraying in the atmosphere may be used, but a better coating can be obtained by low-pressure thermal spraying. Further, depending on the type of alloy, combustion flame may be used, but a better film can be obtained by plasma flame. A carbide powder may be used as a raw material and mixed with an alloy powder for thermal spraying, or an alloy powder containing carbide may be used as a raw material. When using carbide powder, the particle size is preferably finer, preferably about 200 mesosh or less.

Although the present invention is limited to carbides of tungsten and chromium, it is also effective to add other carbides (for example, carbides of molybdenum, silicon, boron, vanadium, etc.) if desired.

l In order to improve the adhesion between the sprayed skin model 1 and the base material of the part, the base treatment is generally silithoblasted, but if necessary, an appropriate alloy (for example, nickel-aluminide) may be thermally sprayed in advance. It is also good to leave it there. Further, the adhesion can be changed to several colors by performing a post-heat treatment if necessary.

The thickness of the sprayed alloy layer according to the present invention can be appropriately set as required, but generally 0.1 to 0.5+u is sufficient.

The material of the metal member is not particularly limited, and generally includes Ril pipes and steel plates, such as boiler tubes of coal-fired boilers.

As already mentioned, the sprayed alloy layer in the present invention includes:
Tungsten and/or chromium carbide is contained in a volume percentage of 15 to 50%, but if the carbide content is less than 15% by volume, sufficient high temperature particle erosion resistance cannot be obtained, whereas if it exceeds 50% by volume This decreases the toughness of the thermally sprayed coating and, on the contrary, decreases the erosion resistance. Therefore, in the present invention, the amount of carbides contained in the sprayed alloy layer is limited to 15 to 50% by volume.

In the present invention, as described above, at least one of molybdenum, silicon, boron, and vanadium carbides may be added, if desired. Limit the amount of carbide to 15-50% by volume. There is no noticeable difference when the sprayed alloy is a cobalt-based alloy or a nickel-based alloy, but the same difference is observed even if the volume fraction of total carbides is slightly lower in the cobalt-based alloy than in the nickel-based alloy. You can also iM the effect.

Next, the present invention will be further explained with reference to Examples, but these are shown as illustrations of the present invention and are not intended to limit the present invention in any way. In this specification, "%" means "% by weight" unless otherwise specified.

A thermal spray coating with a thickness of 0°5 was formed on a JIS 5t1S304 stainless steel base material by plasma spraying using powder of an alloy having the composition shown in Table 1. A high-temperature particle erosion test piece (three dragons thickness x 2Q + am width x 30 mm length) with the above-mentioned thermal spray coating left on one side was prepared from the blank plate, and a high-temperature particle erosion test was conducted as described below. The material of alloy number 10 in Table 1 is used for comparison and is JIS SUS 304 stainless steel bare material.

The above high temperature particle erosion test is performed using the Plast method 11''-
The tests were carried out using John's test equipment. That is, solid particles (
In this example, coal combustion ash with an average particle size of 15 μm was used) and A
r gas and heated separately to 650℃, mixed them at the inlet of a tuna nozzle with an inner diameter of 4, and after accelerating in the nozzle, 650℃.
It was made to collide with a test piece kept at 50°C. The gas flow velocity when colliding with the test piece was 50 m/s and 100 m/s,
In each case) 600 g of solid particles were bombarded with the test surface over a period of 1 hour.

After the test, the thinned area formed at the center of each test piece was measured using a surface roughness meter to determine the maximum amount of thinned metal, and the resistance of each sample material to high-temperature particle erosion was evaluated. The results are also summarized in Table 1.

As is clear from the results shown in Table 1, when the total carbide content is as low as 11% or less, as in the comparative example, even though the thermal spraying method was adopted, the control JIS
No significant improvement was observed compared to 5US304 bare material.

However, in contrast, in the case of a metal member provided with the thermal sprayed alloy layer according to the present invention, a remarkable improvement in high-temperature particle erosion resistance is observed.

Thus, according to the present invention, a metal member having excellent resistance to high-temperature particle erosion can be obtained, and the present invention greatly contributes to the practical application and spread of high-temperature energy devices, which have been attracting attention in recent years.

Applicant: Sumitomo Metal Industries, Ltd. Agent: Patent Attorney Akira Hirose -

Claims (1)

[Claims] A metal component having excellent resistance to hot particle erosion, comprising a thermally sprayed alloy layer containing 15 to 50% by volume of total carbides, including carbides of chromium and/or tungsten.