KR20030064121A - A method for simultaneous aluminizing and chromizing treatment - Google Patents

Abstract

PURPOSE: A simultaneous aluminizing and chromizing treatment method capable of simultaneously diffusing aluminum and chromium by vacuum heat treating or atmospheric heat treating the slurry coated substrate or related product after coating a slurry comprising metal powders, solvent and binder on an iron based substrate and related product. CONSTITUTION: The method comprises a step (a) of preparing a liquid mixed slurry by mixing the mixture with organic solvent and binder after mixing aluminum powder and chromium powder as elements to be diffused with third metal powder as diffusion controlling element in a certain mixing ratio; a step (b) of removing the organic solvent and binder by drying the slurry coated material inside constant temperature dryer after coating the liquid slurry on the surface of a material to be treated by spraying the mixed slurry injected into a sprayer onto the surface of the material to be treated or dipping the material to be treated into the mixed slurry; and a step (c) of forming a diffusion coating layer in which aluminum and chromium elements are simultaneously diffused by heat treating the solvent and binder removed material to be treated at a target temperature for a certain period of time under the vacuum condition or at an atmosphere of inert gas such as argon after charging the solvent and binder removed material to be treated into reaction tube fabricated to enable atmosphere to be controlled during heat treatment.

Description

A method for simultaneous aluminizing and chromizing treatment

In the case of alloying by adding aluminum (Al) or chromium (Cr) component to the iron-based substrate and related products, aluminum or chromium having a high affinity for oxygen is selectively oxidized to form a protective film on the surface of the substrate. In addition to improving the oxidation resistance, the mechanical properties of the substrate are also known to be improved. However, since alloys containing such aluminum or chromium components are fragile and have poor machinability, the surface treatment technology changes only those surfaces appropriately for use characteristics after processing using a substrate having a composition that is easy to process. For example, an aluminizing treatment for diffusing coating with aluminum or a chromizing treatment for diffusing coating with chromium is mainly used. In recent years, as a method for simultaneously improving mechanical properties such as hardness and abrasion resistance, and corrosion and oxidation resistance of the diffusion coating layer, A method of diffusing branch elements has been attempted, and a two-step aluminizing and chromizing process has now been developed for diffusing and coating chromium and aluminum one by one.

However, the above treatment method is not only complicated and cumbersome in the diffusion treatment process, but also difficult to control the concentration and thickness of the diffusion coating layer, and also deteriorates the corrosion resistance and mechanical properties due to the irregular concentration distribution of the penetrating element in the diffusion coating layer. It is implicated.

The present invention has been devised to solve the problems of the conventional aluminizing and chromizing treatment methods. The present invention is applicable to a complex shape, which is a feature of the present invention, and has advantages of being able to control the concentration and thickness of aluminum in the diffusion coating layer. It is possible to simultaneously diffuse and coat aluminum and chromium while keeping it as it is, so that the mechanical properties such as hardness and abrasion resistance of the parent material, which are disadvantages of the method of diffusing only a single element, and the improvement of corrosion resistance and oxidation resistance, can be achieved at the same time. It provides an excellent simultaneous aluminizing and chromizing treatment method, and complements the problem of liquid slurry such as flowing down when the liquid slurry is sprayed or deposited on at least part or the entire surface of the material to be processed to improve the completion of the treatment process. The purpose is to increase.

1 is an optical microscope of a cross section of a workpiece subjected to simultaneous aluminizing and chromizing treatment using a slurry of Al-Ti-5% Cr weight composition ratio in a rod-shaped (Φ50mm) S45C carbon steel as an embodiment of the present invention. Picture.

2 is a cross-sectional view of a workpiece (Φ50mm) subjected to simultaneous aluminizing and chromizing treatment using a slurry of Al-Ti-5% Cr weight composition ratio in a rod-shaped (Φ50mm) SKD61 tool steel according to an embodiment of the present invention. Observed optical micrograph.

3 is an embodiment of the present invention changes the aluminum, titanium and chromium concentration of the diffusion coating layer 20 formed in S45C carbon steel according to the weight composition ratio (Al: Ti) of Al and Ti in Al-Ti-5% Cr slurry Figure showing the thickness change of the diffusion coating layer (20).

4 is a diffusion coating layer 20 in S45C carbon steel subjected to simultaneous aluminizing and chromizing treatment using a slurry of Al-Ti-5% Cr weight composition ratio (Al: Ti = 7: 3) according to an embodiment of the present invention. Figure showing the change in hardness.

<Explanation of symbols for the main parts of the drawings>

10: base material 20: diffusion coating layer 30: enlarged photograph

The present invention is to improve the aluminizing treatment method and apparatus (Patent No. 0312838) of the present invention to achieve the above object, the application of or complementary to the iron-based base material and related surface treatment method In more detail, the method of simultaneous aluminizing and chromizing to improve the heat, wear and oxidation resistance by simultaneously diffusing aluminum and chromium on the surface of the substrate in a one-step process (one-step process) It is about.

In the present invention, the simultaneous aluminizing and chromizing treatment method is to mix the aluminum powder, chromium powder, and the third metal powder (X), which is an element to be diffused, in a predetermined weight composition ratio (Al: Cr: X), It is characterized by using a liquid mixed slurry prepared by mixing in a solvent and a binder.

Simultaneous aluminizing and chromizing treatment method according to the present invention is:

(a) mixing the aluminum powder, the chromium powder, and the third metal powder (X) in a predetermined weight composition ratio (Al: Cr: X), and then mixing them with an organic solvent and a binder to prepare a liquid slurry. ,

(b) injecting the mixed slurry into the injector and spraying or depositing the slurry on the surface of the workpiece to deposit the liquid slurry on the surface of the workpiece, and then removing the organic solvent and the binder in the thermostat. ,

(c) the treated material treated by the above method is charged to a reaction tube made to control the atmosphere during heat treatment, and then subjected to vacuum heat treatment or atmosphere heat treatment for a predetermined time at a desired temperature, and then the process shown in FIGS. It characterized in that it comprises a step of producing a composition in which the diffusion coating layer 20 in which aluminum and chromium elements are simultaneously diffused.

Hereinafter, each component and process steps of the present invention will be described in more detail.

First, in the present invention, the aluminum powder and the chromium powder are the main components constituting the diffusion coating layer 20. On the basis of the weight, the aluminum powder is most preferably adjusted to a composition ratio of twice or more of the chromium powder. Particle selection is important because it greatly affects the properties and diffusion behavior of the mixed slurry, in the present invention it is possible to use the size of -50 ~ -400 mesh, it is preferable to use a powder of -100 mesh or less.

In addition, the third metal powder refers to a component used as an element for controlling diffusion of aluminum and chromium elements during a simultaneous aluminizing and chromizing process, and the composition ratio of the third metal powder is added to the mixed powder of aluminum and chromium. It is characterized in that the concentration and thickness of the diffusion coating layer 20 can be controlled by varying the ratio of 1: 9 to 9: 1 based on the weight.

As the third metal powder, titanium (Ti), magnesium (Mg), molybdenum (Mo), or the like may be used. Particularly, it is preferable to use titanium powder, and the powder particle size is -50 to -400 mesh. These are usable and it is preferable to use powders of -100 mesh or less.

In addition, in the present invention, the solvent, which is a main component for preparing a liquid slurry, may be mixed with a metal powder and the like, so that the solvent may be prepared as a liquid mixed slurry, and the mixing ratio of the mixed powder and the organic solvent may be It is used in an amount of 1.0 to 100 ml per 10 g of mixed powder, preferably 5.0 to 60 ml per 10 g.

In the simultaneous aluminizing and chromizing treatment process, the solvent should be easily removed in the step of removing the solvent so as not to affect the properties of the substrate 10 and the diffusion coating layer 20, such as alcohol, acetone, isopropyl alcohol, It is preferable to use organic solvents such as ethylene glycol, propylene glycol and glycerin.

In addition, in the present invention, the binder is an auxiliary additive added to compensate for the problem of using a liquid slurry, such as flowing down when the liquid slurry is sprayed or deposited on the surface of the substrate. And organic binders such as polyvinyl alcohol (PVA), polyvinyl butynal (PVB), wax, starch, etc., because they must be easily removed in the step of removing the solvent and binder so as not to affect the properties of the diffusion coating layer 20). It is preferable to use, the mixing ratio with the organic solvent is used in an amount of 0.01 to 30g per 25ml, preferably 0.02 to 20g per 25ml.

In addition to the binders exemplified above, any auxiliary material capable of improving the properties of the mixed slurry according to the present invention, for example, controlling the fluidity of the slurry and wettability with the material to be treated can be used.

After adding the above components at a constant composition ratio, in order to perform the simultaneous aluminizing and chromizing treatment of the present invention, it is necessary to prepare the components in the form of a mixed slurry in which each component is uniformly dispersed. The process of uniformly mixing the organic solvent and the binder component should be carried out.

The mixing process is performed by stirring for 1 to 20 minutes with a general stirrer using a magnetic bar rotating at a rotational speed of 100 to 2,000 rpm, it is possible to obtain a liquid slurry in a gel or paste state.

The slurry of the liquid mixture dispersed and mixed by the above process is deposited or deposited on at least a part or the entire surface of the iron-based substrate and related products by using a spraying device, and then vacuum or argon (Ar) for a predetermined time at a desired temperature. Simultaneous aluminizing and chromizing treatments are performed to diffuse aluminum and chromium at the same time by performing heat treatment in the atmosphere in which inert gas is injected.

Hereinafter, the present invention will be described in more detail with reference to the physical properties of the simultaneous aluminizing and chromizing treatment method and embodiment according to the present invention.

The following examples are provided to illustrate and explain the present invention in more detail, and the scope of the present invention should not be understood as being limited only to the following examples.

<Example 1>

This embodiment uses titanium powder (-200 mesh) as the diffusion control element in aluminum powder (-200 mesh) and chromium powder (-200 mesh), which are the target elements for diffusion, and the weight of chromium based on the total weight of the powder. The composition ratio was kept constant at 5%, the remaining 95% of aluminum and titanium were quantified at a weight ratio of 7: 3, and then the mixed powder of the weight composition ratio was mixed with polyvinyl alcohol (PVA) as isopropyl alcohol as an organic solvent. The liquid slurry was prepared by mixing the dissolved liquid phase. At this time, the composition ratio of the organic solvent was added to 5ml per 10g mixed powder using a binder dissolved in 1.0g per 25ml of organic solvent, and also 300 rpm of a general stirrer using a magnetic bar for uniform mixing of metal powder and organic solvent. Stirring was carried out for 10 minutes at speed. The liquid slurry prepared as described above was injected into the injector and sprayed to attach the slurry to the surface of the rod-shaped (Φ50mm) S45C carbon steel, and then held in a constant temperature dryer maintained at 200 ° C. for 30 minutes to be included in the slurry. Organic solvent and binder were removed.

The treated material prepared by the above method was charged to a reaction tube for diffusion heat treatment, and the simultaneous aluminizing and chromizing treatments were performed. At this time, in order to prevent oxidation of metal powders during the heat treatment, the inside of the reaction tube was maintained in a vacuum atmosphere of 5 × 10 ^-6 Torr using an exhaust system composed of a rotary pump (RP) and a diffusion exhaust pump (DP). The temperature of the reaction tube was 950 ° C., and the reaction time was 1 hour.

FIG. 1 is a photograph of a cross section of a rod-shaped S45C carbon steel subjected to simultaneous aluminizing and chromizing treatment according to the composition of Example 1, and diffused near the surface of the substrate 10 by diffusion heat treatment at 950 ° C. for 1 hour. It can be confirmed that the coating layer 20 is formed, and as can also be seen in the enlarged photograph 30 of FIG. 1, the diffusion coating layer 20 having a very uniform surface smoothness can be confirmed.

<Example 2>

This embodiment is an example in which the applicability of simultaneous aluminizing and chromizing treatments according to the treated materials is examined by using the tool steel of SKD61 having a different alloy composition from the S45C carbon steel of Example 1 as the treated material. The same treatment process as the mixed slurry of the same composition was performed.

Figure 2 is a photograph of the cross section of the SKD61 tool steel carried out from the present embodiment, it can be seen that the uniform diffusion coating layer 20 is formed in the uniform surface smoothness and the surface vicinity of the treatment agent as in FIG.

Therefore, as shown in Figs. 1 and 2, the simultaneous aluminizing and chromizing treatment of the present invention can be widely used for iron-based substrates containing iron as a main component and all related products. It can be applied to complex shapes as well as rods by spraying or depositing on the surface.

<Example 3>

In this embodiment, the S45C carbon steel having a rod shape (diameter of 50 mm Φ) is used as a material to be treated, and the weight composition ratio of chromium, which is a diffusion target element, is fixed at 5%, and the remaining 95% aluminum and titanium are composed of weight composition ratio (Al: Ti ) And the mixed powder of 10: 0 to 1: 9 was subjected to the same process as the liquid slurry manufacturing process of Example 1, and aluminum and chromium in the diffusion coating layer 20 according to the Al: Ti mixing ratio of the liquid slurry. The change of the concentration and thickness of was investigated, and the hardness change with the depth of the diffusion coating layer 20 was investigated to examine the mechanical properties of the diffusion coating layer 20.

3 is a view showing the concentration change and the thickness change of the aluminum and chromium, which is the element to be diffused in the diffusion coating layer 20 according to the Al: Ti mixing ratio of the liquid slurry, the diffusion heat treatment was the same at 950 ℃, 1 hour Elemental analysis of, aluminum and chromium was evaluated in the same manner on the basis of the point 10㎛ from the surface of the diffusion coating layer (20). As shown in FIG. 3, the aluminum concentration of the diffusion coating layer 20 decreased almost linearly as the composition ratio of titanium, the diffusion control element, increased, and the thickness of the diffusion coating layer 20 gradually decreased, but the chromium concentration in the diffusion coating layer 20 was decreased. Was found to be approximately 3-4 at.% Regardless of the Al: Ti mixing ratio.

Therefore, the simultaneous aluminizing and chromizing treatment method of the present invention can not only control the aluminum concentration in the diffusion coating layer 20 and the thickness of the diffusion coating layer 20 by controlling only the weight composition ratio of titanium, which is an element for diffusion control, but especially aluminum. It was confirmed that addition of chromium powder to titanium powder and titanium powder can form a diffusion coating layer 20 in which aluminum and chromium are mixed.

4 is a slurry of S45C carbon steel to be treated using a slurry having a weight composition ratio (Al: Ti) of aluminum and titanium of 7: 3, and a slurry having the same Al-Ti-5% Cr weight composition ratio as in Example 1. : Ti = 7: 3) shows the change in hardness according to the depth of the diffusion coating layer 20 of the treated material subjected to the simultaneous aluminizing and chromizing treatment. The diffusion of chromium and chromium at the same time was confirmed to increase the hardness by almost two times.

Simultaneous aluminizing and chromizing treatment method of the present invention through various embodiments as described above can be widely used in iron-based substrates and all related products containing iron as a main component, and also spray a liquid slurry on the surface of the material to be treated It is possible to apply to complex shapes as well as rod-like by using or to deposit, and in particular, it is possible to improve the mechanical properties such as hardness and wear resistance of the diffusion coating layer (20).

The present invention relates to a method for surface treatment of iron-based substrates and related products to which the improved aluminizing treatment method and apparatus thereof (Patent No. 0312838) is applied or supplemented, and more specifically, a single treatment process. In the simultaneous aluminizing and chromizing treatment method for improving the heat resistance, abrasion resistance, and oxidation resistance by simultaneously diffusing and coating aluminum and chromium on the surface of the substrate, iron-based iron, which is a feature of the invention, It can be widely used for the substrate and all related products, and can be applied to complex shapes as well as rods by spraying or depositing a liquid slurry on the surface of the material to be treated, and also of the diffusion coating layer 20 Simple and reproducible while maintaining the advantages of aluminum concentration control and thickness control It is possible to improve mechanical properties such as hardness and abrasion resistance of the diffusion coating layer 20 by simultaneously diffusing aluminum and chromium, and also liquid phase such as flowing down when the slurry is sprayed or deposited on at least part or the entire surface of the material to be treated. The problem of using the slurry of polyvinyl alcohol (PVA), polyvinyl butynal (PVB), wax, starch, etc. by adding a binder of organic substances, such as supplement, by the simultaneous aluminizing and chromizing treatment method of the present invention It is characterized by increasing the completeness.

Claims (6)

In the improved aluminizing treatment method and apparatus (Patent No. 0312838), the iron-based substrate and the method for surface treatment of the related products, which has applied or supplemented the previously filed invention, (a) After mixing the aluminum (Al) powder and chromium (Cr) powder as the diffusion target element and the third metal powder (2) as the diffusion control element at a constant weight composition ratio (Al: Cr: X), it is an organic material system. Mixing a solvent and a binder to prepare a liquid mixed slurry; (b) injecting the mixed slurry into the injector and spraying or depositing the slurry on the surface of the workpiece to deposit the liquid slurry on the surface of the workpiece, and then removing the organic solvent and the binder in the thermostat. ; (c) charging the treated material treated by the above method into a reaction tube made to control the atmosphere during heat treatment, and then injecting an inert gas such as vacuum or argon (Ar) for a predetermined time at a desired temperature. And performing a heat treatment to form a composition in which a diffusion coating layer 20 in which aluminum and chromium elements are simultaneously diffused is formed. The method of claim 1, Simultaneous aluminizing and chromizing treatment method, characterized in that the diffusion target element contains chromium. The method of claim 1, The total composition ratio of the diffusion target element and the diffusion control element is 0.5 to 40% by weight of chromium, 5 to 90% by weight of aluminum, 5 to 90% by weight of the third metal powder (X) Simultaneous aluminizing and chromizing treatment method characterized in that it is carried out at the composition ratio. The method of claim 3, wherein And the composition ratio of the aluminum powder and the chromium powder, which are the diffusion target elements, based on the weight, to control the aluminum powder to a weight composition ratio of at least two times that of the chromium powder. The method of claim 1, The composition ratio of the binder is 0.01 to 30g per 25ml of organic solvent is added, the simultaneous aluminizing and chromizing treatment method. The method of claim 5, And the binder is one or a mixture of two or more selected from organic materials such as polyvinyl alcohol (PVA), polyvinyl butynal (PVB), wax, starch and the like.