JPS5934230B2 - Metal surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for improving the corrosion resistance and heat resistance of metals.

Traditionally, one of the surface treatment methods for improving the corrosion resistance and heat resistance of metals is the thermal spray plating method.
Zn, At, etc. are used for corrosion resistance for parts such as steel towers and bridges used in corrosive environments, and heat-resistant materials are used for parts used in high-temperature environments such as gas turbines, boilers, heating furnaces, and incinerators. At, Ni--At alloy, Ni--Cr alloy, etc. are used for the purpose of improving properties. However,
This kind of thermal spray plating film is porous and usually has a thickness of 5 to 20%.
Because it has a moderate porosity, it has poor airtightness, and because the film and base material do not form a sufficient diffusion layer, it has poor adhesion.

For this reason, the thermal spray plating film has the disadvantage that it is easily penetrated by liquids and gases such as water and air, and is also easily peeled off due to vibration, thermal expansion, bending stress, etc. Currently, to address the defects in airtightness, methods are being used to fill the voids by applying various paints or solvents on the film, and to address the defects in adhesion, methods are used to fill in the voids after the film is formed. A method has been used in which the film is heated and melted to form a diffusion layer between it and the base material, but the former has the disadvantage that it cannot be applied to parts that are heated, and the latter has the disadvantage that the sprayed metal has a high melting point. The disadvantage is that metals cannot be used.

The present invention was made in order to eliminate the drawbacks of the conventional methods as described above, and compared to the conventional methods, the film has better airtightness and adhesion, and can be applied to a wider range of parts. ,
At the same time, the present invention provides a metal surface treatment method that significantly improves the corrosion resistance and heat resistance of the base material.

That is, the present invention improves the airtightness and adhesion of the plated layer by applying chemical vapor phase plating of the metal to the plated layer that has been thermally spray plated to improve the heat resistance and corrosion resistance of the base material. This is a metal surface treatment method characterized by the following.

Hereinafter, the present invention will be specifically explained with reference to Examples.

(Example 1) Commercially available Ni-based alloy (Ni-balance-Cr: 1
5% - Ti: 2.5%) with a diameter of 20 mm and a length of 50 mm.
After processing into a cylindrical shape and shot blasting the entire surface, Ni and Ni: 60%-
Cr: 40% alloy, Ni: 95%-A ■ 5% alloy 0
．． The material to be treated was thermally spray plated to a thickness of 5 mm.

Next, Cr
, At was chemical vapor plated. Chemical vapor phase plating of Cr particles: 60%, At203: 39%, NH4Ct
The treatment was carried out using a treatment agent of :1% by the method shown in FIG. 1, by treating at 1050° C. for 5 hours while passing H2 gas. In addition, At chemical vapor plating is performed using At powder: 10%-A403■88%-NH4Cι2
% of the treatment agent and the same method as shown in FIG. 1, the treatment was carried out at 1000° C. for 3 hours while passing H2 gas. Next, the airtightness, adhesion, heat resistance, and corrosion resistance of the film subjected to the surface treatment of the present invention were tested, and the results shown in Tables 1 to 5 were obtained.

According to this result, the film subjected to the surface treatment of the present invention has
It can be confirmed that airtightness, adhesion, heat resistance, and corrosion resistance are significantly improved compared to a film that is not subjected to the surface treatment of the present invention (a film that is only coated with back-ply plating). In addition, each characteristic test of the film was conducted as follows. In other words, the airtightness test is performed by measuring the porosity of the cross section of the film using an optical microscope, and the adhesion test is performed by repeatedly subjecting the film to rapid heating (10
000C) and rapid cooling (20℃) and measuring the number of times until the film peels off.
The corrosion resistance test was conducted by continuously heating the film for 300 hours in an electric furnace at 00°C and measuring the weight change before and after.
50℃ high-melt salt (V2O5:80%-Na2sO4:2
0%) and molten salt at 900℃ (Na2SO4:90%-
This was done by heating each sample continuously for 100 hours in Nact: 10%) and measuring the change in weight before and after that. By the way, the characteristics of the film subjected to the surface treatment of the present invention are improved as described above because of the treatment agent Cr (or At) and N.
H4Ct reacts with H2 gas to form Crct2 (or A
tCt3) vapor is generated and invades the voids of the blast plating film of the treated material, where it is reduced by H2 gas and precipitated as Cr (or At).
This is thought to be because the voids in the irradiated plating film are filled with Cr (or At).

In addition, Cr (or At) reduced by H2 gas in areas other than the voids is also very fine, so it easily invades and fills the voids, and the Cr (or At) reduced by H2 gas Cr (or At
) has an extremely large activation force, so it is thought that the alloying reaction with the irradiated plating metal and the base material is active, promoting metallurgical bonding with these and improving adhesion.

Table 1: Airtightness test results (measured porosity) Table 2: Adhesion test results (measured number of repetitions) Table 3: Heat resistance test results (measured weight change*) Table 4: Corrosion resistance test results ( Measured value of weight change*) Table 5 Corrosion resistance test results (measured value of weight change*) (Example 2) Commercially available CO-based alloy (CO: remaining -Cr:25%-1!Ni
:10(f)) was subjected to radiation plating and chemical vapor plating in the same manner as in Example 1, and the airtightness, adhesion, heat resistance, and corrosion resistance of the film were tested. We obtained results almost similar to those in the table.

Further, chemical vapor plating can also be carried out by the methods shown in FIGS. 2 and 3, and can also be carried out by using an inert gas such as N2 gas or Ar gas. (Example 3) Commercially available stainless steel cast steel (Fe: balance - Cr: 18% - Ni
:10%-C:0.35%) was processed and shot blasted in the same manner as in Example 1, and the Cr:20%-Fe:80% alloy was processed using the acetylene gas method. 5
It was plated to a thickness of 7 nm.

''～Next, Cr is applied on the plated film using the method shown in Figure 3.
Chemical vapor phase plating was applied.

The adhesion, heat resistance, and corrosion resistance of the film subjected to the above surface treatment were tested in the same manner as in Example 1, and as shown in Table 6, it was confirmed that each property was significantly improved. Now, the surface treatment method of the present invention has the following characteristics.
(1) Compared to conventional radiation plating, the plating layer has better airtightness and adhesion.

Additionally, as a result, heat resistance and corrosion resistance are also improved. (2) The disadvantages of chemical vapor plating, such as the combination of chromium-plated metal and chemical vapor plating metal, are that the base material with high carbon content has poor diffusivity even when chemical vapor plating is applied with Cr. Since the drawbacks such as the inability to obtain a thick plating layer due to the formation of a Cr carbide layer are solved, the applications of AV1 can be expanded regardless of the composition of the base material.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are diagrams each showing an embodiment of the metal surface treatment method of the present invention. Figure 1 shows the material to be treated after surface plating being buried in the treatment agent in the processing container, and Figure 2 shows the material being treated using a perforated plate.
Fig. 3 shows a state in which the plating container is separated into a plating gas generation section and a plating section, and a state in which the plating processing container is separated into a plating gas generation chamber and a plating chamber by a connecting pipe. In Figures 1, 2, and 3, 1...: Processing container, 2...
...Gas introduction port, 3...Nozzle, 4...
-・Processing agent, 5...Material to be treated, 6''゜'゜゜Gas exhaust port・1・---Porous plate, 8...---Plating gas generation chamber, 9... ...Connection pipe, 10...
...Metsuki room.

Claims (1)

[Claims] 1. A metal chemical vapor phase plating is applied to the plated layer which has been thermally spray plated to improve the heat resistance and corrosion resistance of the base material, thereby improving the airtightness and adhesion of the solvent plated layer. A method for surface treatment of metals.