JPS62116784A - Method for restoring hardness of film formed of powder - Google Patents

Abstract

PURPOSE:To restore the hardness of a film formed of powder and to improve the adhesiveness to a base body by irradiating a laser to a steel base body on which powder is coated and the film thereof is formed while preheating said body to weld the film material to the base material then subjecting the base body to a heating treatment to a specific temp. CONSTITUTION:The film is formed on the surface of the steel base body by coating the powder thereon. While the above-mentioned base body is preheated to and held at >=350 deg.C, the laser is irradiated to the film to heat the film material to the temp. above the m.p. The base body and the film are thereby welded at the boundary part thereof. The base body is then heated to 200-700 deg.C and is cooled. The characteristics such as hardness intrinsically possessed by the above-mentioned film formed of the powder are thereby restored and the film- formed body which does not exfoliate and crack, is substantially strong and excels in wear resistance, etc., is thus formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating steel products having a powder-formed coating on the surface of a substrate.

[Prior art]

In order to impart corrosion resistance or wear resistance to recent steel products,
Instead of plating, there is a method of thermal spraying metals such as Cu+N++Co, Cr, T++Mo, alloys or oxides of these metals, which have corrosion resistance, wear resistance, and heat resistance. This method has excellent adhesion by melting it in liquid form and attaching it to the base material to form a film.Although the adhesion is slightly inferior, this method provides corrosion resistance and abrasion resistance very easily. One method is to apply the powder directly to the base material.

This is a method in which powders of the above-mentioned metals and their alloys or oxides are mixed with a liquid resin paint or a liquid such as alcohol, and the mixture is applied to a substrate using the wettability of the liquid to form a film. It is. However, since the film formed in this manner is simply a state in which powder particles are bonded by solidified liquid, pores are likely to exist and defects such as cranks are likely to occur. In order to eliminate these defects, one method is to at least partially melt and bond the powder by laser irradiation.

However, the cooling rate of such a powder-coated film melted by laser irradiation is extremely fast, approximately 1000°C/SeC, and there is a problem that the surface condition deteriorates as well as hardening due to martensitic transformation after heating the material. In order to reduce the influence, preheating is performed at a temperature of 350° C. or higher before radar irradiation.

[Problem that the invention seeks to solve]

Depending on the method of laser irradiation while performing this preheating, on the one hand it is possible to prevent cracking etc. during solidification of the powder coating, but the drawback is that the hardness of the coating itself decreases due to dilution with the material. There is.

In other words, the wear resistance of the formed film is reduced.

The present invention solves the above-mentioned problems caused by irradiating a coating formed using powder with a laser, thereby recovering the deterioration of the inherent characteristics of the base material and coating, and improving the properties of the coating itself. The purpose is to improve the characteristics.

[Means for Solving the Problems] The above object of the present invention can be achieved by heating the coating at a specific temperature after being melted by laser irradiation.

After the coating melted by laser irradiation solidifies, the formed coating and the steel surface in contact with it are allowed to penetrate each other with alloying elements, creating a supersaturated solid solution of elements other than those required for each other to exhibit their properties. It is in an unstable crystalline state.

Therefore, by heating the fused film by laser irradiation, intermetallic compounds and carbides containing elements from the base material as a solid solution can be precipitated between the grains, thereby restoring the hardness of the film.

Although the heating temperature after laser irradiation strictly depends on the material or base material of the powder-forming film, it is possible to sufficiently recover the hardness of the powder-forming film by heating to a temperature range of 400 to 700°C. It is possible.

In addition, the heating time for this purpose is sufficient as long as the powder-formed coating is heated uniformly; if the heating time is too long, the intermetallic compounds and carbides precipitated at the grain boundaries will be re-dissolved in the molten powder layer, causing a decrease in hardness again. It turns out.

Furthermore, the post-heating also restores the toughness of the heat-affected zone of the substrate that has deteriorated due to laser irradiation.

〔Example〕

After cleaning the surface of a steel plate with length 1000ss, medium 500-1, and thickness 1Olong by shot blasting, a powder alloy having the composition shown in Table 1 was added statically to the steel plate for 500mm.
It is impeded to a thickness of pm.

Table 1 This powder-coated steel plate was heated to 400° C., and while the temperature was maintained, a CO2 laser with an expansion power of 5 was irradiated at a speed of 0.1 s/11 inch in the atmosphere. After irradiation, 20
The temperature was maintained at 0°C, 400°C, 600°C, and 800°C for 30 minutes and 60 minutes, respectively.

Figure 1 shows the cross-sectional hardness of the powder-formed corrugated membrane after heating;
The figure shows changes in the heat-affected zone of the base body due to the above-mentioned heating.

As shown in Figure 1, the hardness of the cross section of the coating is 30 minutes and 6 minutes.
It can be seen that in both cases of 0 minute holding, the hardness recovered at 200°C, reached a peak at 600°C, and decreased again at 800°C. Furthermore, as shown in FIG. 2, it can be seen that the hardness of the heat-affected zone of the base body finally decreases, and the toughness is restored.

〔Effect of the invention〕

According to the present invention, it is possible to sufficiently achieve the inherent functions of laser irradiation, which are to improve the adhesion of the powder-formed film to the substrate and to improve the properties of the formed film, and to improve the peelability and crackability from the powder. It is possible to obtain a film-forming body having sufficient strength without any heat loss.

[Brief explanation of drawings]

The attached figure shows the state of recovery of the properties of the powder-formed coating and the heat-affected zone of the substrate by heating after laser irradiation.

Claims (1)

[Claims] 1. Apply powder to the surface of a steel substrate to form a film, and while maintaining the substrate at a temperature of 350° C. or higher, irradiate the coating with a laser to heat the coating material to a temperature above the melting point; A method for recovering the hardness of a powder-formed coating, which comprises fusing a steel substrate and the coating at an interface thereof, then heating to a temperature of 200 to 700°C and cooling.