JPS5814504B2 - Kinzoku Hiyou Menshiyorihou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method suitable for improving mechanical strength such as heat resistance, corrosion resistance and abrasion resistance of metal surfaces.

In recent years, the environmental conditions for metal materials used in various plants have become harsher, causing corrosion, oxidation,
Alternatively, there has been a demand for materials that are stable against wear, and a manufacturing method for metal materials that strengthens only the surface has become necessary.

Plating or post-plating heat treatment is applied to the surface of the metal material,
Although it is well known that it is used as a surface reinforcement material,
In this case, the adhesion between the plated layer and the base material is poor and the plated layer peels off, or the plated layer develops into columnar crystals that reduce ductility and cause cracks in the plated layer.Also, if the plated layer is not heat-treated after plating, it may become coarse. There were drawbacks such as a decrease in mechanical strength due to the development of crystals.

The present invention was proposed for the purpose of eliminating the above-mentioned drawbacks, and after subjecting the surface of stainless steel to shot brightening, the surface is plated with Ni or Cr, and after the plating, the plating is further applied. The layer is shot blasted, and then the plated layer is heated to 850 to 950°C, so that the plated metal is deeply diffused into the base metal by the recrystallization recovery energy of the plastically deformed portion of the base metal and the plated layer. Provides a surface treatment method for

In the present invention, shot blasting is applied to the stainless steel surface before plating, and shot blasting is further applied to the plated surface after the plating is suppressed, so that plastic deformation occurs in the subsequent heat treatment process. The crystal lattice is rearranged (polygon
As the crystal distortion caused by plastic deformation is released, adjacent crystals crush each other and grow, so the boundary between the plated layer and the base metal disappears, and the plated metal is deep inside the base metal. Spread.

This phenomenon is unlikely to occur unless shot blasting is applied to the base material surface layer and the plating layer.

In addition, the higher the temperature, the faster the diffusion due to heat treatment, but on the other hand, if the temperature is too high, the crystal grains will become coarse and the mechanical properties will deteriorate, so the heating temperature should be 850 to 950, considering the balance between the diffusion rate and the crystal grain size. °C is appropriate.

Next, embodiments of the present invention will be described based on the drawings.

Figures 1 and 2 are diagrams showing the present invention in the order of steps. Figure 1 shows 1.
After applying shot blasting using shot 1 to the surface of the 8Cr-8Ni stainless steel material, Ni plating 4 was applied by ion plating, and then shot blasting was applied again on the Ni plating layer 4, as shown in Fig. 2. After that 90
The case where heat treatment was performed at 0° C. for 60 minutes is shown.

The Ni plating layer 4 in FIG. 1 has been distorted due to the shot blasting process performed again with shot 1.

2 shows the surface layer of the 18Cr-8Ni stainless steel which was significantly strained by the initial shot blasting treatment, and 3 shows the part that was not strained.

In addition, 5 in Figure 2 shows a diffusion layer in which the plated metal is deeply diffused into the base material by heat treatment, and the lattice rearrangement progresses due to the recovery energy of the crystal that has strain energy generated by plastic deformation, and due to plastic deformation, the lattice rearrangement progresses. As the strain in the crystals is released, adjacent crystals grow by crushing each other, so the boundary between the plating layer and the base material disappears, and the plated metal is deeply diffused into the base material.

Furthermore, since plastic deformation is applied to the plated layer through shot blasting, the crystal grains do not become coarse.

In this example, by subjecting the base material surface layer and the plating layer to shot blasting, the Ni plating material diffuses deeply into the base material, resulting in good adhesion of the plating layer and fine grain size. , and a deep diffusion layer was obtained.

Furthermore, since the plating material is Ni, it has good corrosion resistance and wear resistance, and since shot blasting is used for plastic deformation, it can be applied to complex parts.

The plating metals used include Ni and Cr.
Objects suitable for applying the present invention include turbine blades, boiler tubes, gears, and the like.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing the steps of applying an embodiment of the present invention to 18Cr-8Ni stainless steel. 1... Shot, 2... Surface layer subjected to strain, 3... Portion not subjected to strain, 4... Plating layer, 5... Diffusion layer.

Claims (1)

[Claims] 1 After performing shot blasting on the surface of stainless steel, plating the surface with Ni or Cr, further performing shot blasting on the plated surface, and then heat treating the plated layer at 850 to 950 ° C. A surface treatment method characterized by: