JPH0357178B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-resistant thermal spraying alloy material, particularly to a thermal spraying alloy powder that is resistant to high-temperature corrosion. Oil prices have risen markedly in recent years, and low-quality oil with high sulfur and vanadium contents is on the rise. Under these circumstances, energy saving technology and technology to utilize low-quality oil have become extremely important. By the way, many of the parts used at high temperatures, such as combustion chambers of gas turbines that use heavy oil as fuel, heating furnaces for oil refineries, etc., are required to have corrosion resistance at high temperatures in addition to heat resistance. Particularly in situations where heavy oil with high sulfur and vanadium contents must be used, the conventionally used chrome steel and nickel chrome steel have insufficient corrosion resistance at high temperatures, which limits the range of use. be. In order to overcome this difficulty, thermal spray processing methods have shown remarkable progress, and techniques have been adopted to extend the service life of parts by thermally spraying them with high-temperature corrosion-resistant materials on the surfaces of parts used at high temperatures. A specific example is Ni
Ni-Cr-Al-Y based alloys have been proposed and have been effective in some applications. However, Ni-based Ni-Cr-Al-Y alloys have a high vanadium concentration, and when used in high-temperature environments, they do not necessarily have sufficient corrosion resistance and cannot maintain their function as a protective film. It's becoming a problem. The present invention provides an alloy powder material for thermal spraying that exhibits sufficient corrosion resistance even in a high-temperature corrosive environment with a high vanadium concentration. That is, the first feature of the present invention is that the main component is chromium, which is resistant to vanadium attack, to which aluminum and yttrium are added, and the remainder is nickel, and further improves the toughness and adhesion of the film at high temperatures. The second feature is that at least one of lanthanum and cerium is added to the alloy in order to achieve this. The content of each component of the present invention was determined as described above because it was determined as an effective range after considering the heat resistance, corrosion resistance, thermal shock resistance, toughness, and adhesion between the film and the base material of the film. . That is, chromium is necessary to impart heat resistance and corrosion resistance to the alloy of the present invention, and in particular, a chromium-based alloy is used to resist vanadium attack at high temperatures. If the chromium content is less than 50%, sufficient effect against corrosion by vanadium at high temperatures will not be obtained, and if it exceeds 70%, the film will become brittle and the adhesion to the base material will weaken, making it impractical. Aluminum forms an intermetallic compound with chromium and is effective against oxidation and corrosion by sulfur at high temperatures. If the amount added is less than 2%, the effect will be weak, while if it exceeds 15%, the sprayed coating will become brittle. When added at the same time as aluminum, yttrium has an effect on the corrosion and oxidation resistance of the sprayed coating. This is because if the amount added is less than 0.1%, the effect is insufficient, and if it exceeds 3.0%, no extension of the effect is observed and it is not economical. The reason why the remainder was made of nickel was to impart toughness to the thermal sprayed coating without impairing its heat resistance and corrosion resistance, and to improve its adhesion to the base material. Furthermore, the selective elements lanthanum and cerium are rare earth elements with similar properties to yttrium, but when added at the same time as yttrium, they improve the toughness of the film, and are particularly effective in preventing cracking and improving peeling resistance of the film. It turned out to be true. Addition amount is 0.1 of at least one of lanthanum and cerium.
% to 3.0% is appropriate. If it is less than 0.1%, the effect is weak, and if it exceeds 3%, no improvement in the effect is observed. Next, the present invention will be described in detail with reference to examples. EXAMPLE An alloy having the composition shown in Table 1 was made into a powder by a conventional melt-refining method, and then classified to adjust the particle size to a range of 10 to 44 μm to obtain a material for thermal spraying. 40mm square 2mm by plasma spraying using these alloy powder materials.
A 0.3 mm thick thermal spray coating was applied to both sides of a thick Hastelloy C test piece. The thermal spraying conditions were as follows. Arc gas: Ar: Hr = 3:1, 50/min Voltage: 34 V Current: 800 A Powder supply rate: 30 g/min Next, these specimens were subjected to vanadium attack tests, oxidation tests, and thermal shock tests at high temperatures. carried out. Vanadium attack test is 85%V ₂ O ₅ -15%
After applying the Na ₂ SO ₄ solution, it was kept at 1050°C for 3 hours in an electric furnace, then taken out, and the application and heating were repeated 3 times, followed by descaling treatment, and the degree of corrosion was examined by weight changes before and after the test. For the oxidation test, the test piece was held at 1100°C for 100 hours in a furnace in an atmospheric atmosphere, and the oxidation weight gain was measured over time. In the thermal shock test, the sample was kept in a furnace at 1050°C for 3 hours and then cooled with water repeatedly, and the number of repetitions until the thermal spray coating peeled off was determined. The results of the vanadium attack test and the thermal shock test are shown in Table 1, and the results of the oxidation test are shown in FIG. In addition, as a comparative example, the results of a similar test performed by thermal spray coating with conventionally used Ni-Cr-Al-Y alloy (No. 5) and Cr-Ni alloy (No. 6) are also shown.

[Table] From the results in Table 1, No. 1 ~ containing 50% or more chromium and simultaneously containing aluminum and yttrium
It can be seen that No. 4 and No. 7 have excellent vanadium attack resistance. However, No. 7, which has a high aluminum content, is not suitable because the film becomes brittle and easily peels off. Also added lanthanum and cerium.
In addition to vanadium attack resistance, No. 3 and No. 4 were found to have significantly improved thermal shock resistance. According to FIG. 1, in No. 6 and No. 8 to which yttrium was not added, a considerable increase in oxidation weight was observed. Furthermore, in No. 7, which had a high aluminum content, cracks occurred in the coating, which caused abnormal oxidation. As explained above, according to the present invention, a strong thermal sprayed coating with excellent vanadium corrosion resistance particularly at high temperatures can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the change over time in high-temperature oxidation weight gain of a specimen coated with the heat-resistant sprayed alloy according to the present invention.

Claims (1)

[Claims] 1. A heat-resistant thermal spray alloy material, characterized in that it consists of 50 to 70% chromium, 2 to 15% aluminum, 0.1 to 3.0% yttrium, and the balance nickel. 2. Contains at least one of 50-70% chromium, 2-15% aluminum, 0.1-3.0% yttrium, and 0.1-3.0% lanthanum or cerium by weight.
A heat-resistant alloy material for thermal spraying, characterized in that % and the remainder are made of nickel.