JP3093474B2 - Corrosion and wear resistant parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new corrosion-resistant and abrasion-resistant part, for example, a high-carbon steel, a high-carbon alloy steel, a cast iron, a cast steel, and other iron materials. It relates to parts with excellent corrosion resistance, abrasion resistance, and peel resistance, in which titanium is diffused and infiltrated into the surface of moving parts, bearing parts, pump impeller parts, piping parts, etc., and a coating layer made of titanium carbide is formed on the surface. is there.

[0002]

2. Description of the Related Art Conventionally, in order to improve the wear resistance of a metal material, its surface has been subjected to a carburizing treatment or a nitriding treatment. In particular, components requiring corrosion resistance and abrasion resistance are subjected to hard chrome plating, thermal spraying of WC-Co or the like, chromizing treatment, and the like.

[0003]

In the case of hard chromium plating, plating with a uniform thickness cannot be obtained when the shape of the component is complicated. For example, FIGS. 1 (a) and 1 (b) show a pump impeller 1 in a submersible sand pump used to wind up and suck up soil at the bottom of the water and discharge muddy water containing the earth and sand. Is the cross-sectional view,
(B) is a plan view thereof. The pump impeller 1 has a small opening 3 of the boss 2 and a large lower opening 4. The small opening 3 and the large lower opening 4 allow a drive shaft (not shown) to pass therethrough. Has become. Around the periphery, following the boss 2, the upper surface has a flat portion 5 and the lower surface has a tapered portion 6. Inside the cavity portion 7, a cavity portion 7 is formed. Are separated. At the time of use, when the driving shaft of the stirring blade (not shown) is driven,
Is discharged from the periphery of the shaft through the cavity 7 as shown by an arrow. Since the pump impeller 1 is used in muddy water, corrosion resistance and abrasion resistance are required as a whole. Particularly, since the muddy water passes through the cavity portion 7 at a rapid speed, particularly high corrosion resistance, Abrasion resistance is required.

When hard chrome plating is applied to such a pump impeller 1, the plating thickness in the cavity 7 becomes thin, and if the inside of the cavity 7 is to be adhered to a specified thickness, a remarkably large number of treatments are required. Time is spent. On the other hand, the plating thickness on the outer surface, for example, the outer surfaces of the flat portion 5 and the tapered portion 6 becomes extremely large. In the first place, hard chromium plating has the greatest drawback that it is easily peeled off at the interface due to the structure of physical bonding with the base material. In addition, the surface hardness of hard chrome plating is micro Vickers hardness mHV77.
Therefore, there is a problem that parts used in muddy water such as a pump impeller have insufficient wear resistance.

The WC-Co sprayed material has a surface hardness of m
Although the hardness is high at about HV1,000 and the formed film is hard to peel off and has relatively high peeling resistance, it is difficult to apply a uniform film thickness, and as shown in FIG. Such coating inside the cavity 7 becomes even more difficult, and it is impossible to adapt to a complicated minute component that cannot enter the spray nozzle.

As a means for solving these problems relating to the shape of parts, a chromized material having improved corrosion resistance, abrasion resistance and peeling resistance has been developed. mHV is about 1,000 to 1,800,
It could not withstand use in an atmosphere with strong grinding power and severe wear such as silica sand transport piping and muddy water pump impellers.

In addition, as a method of hardening a surface of a metal, there is known a method in which a step of diffusing and infiltrating a metal such as titanium or zirconium on the surface of a metal material and a step of carburizing are performed in an arbitrary order (Japanese Patent Application Laid-Open No. HEI 1-1990). -177355). According to this method, a carbide layer having a high hardness is formed on the metal surface, and it is said that the wear resistance of the metal surface can be considerably improved. However, there are the following problems. That is, when titanium is first diffused and infiltrated according to this method, and then carburized, the surface of the metal material is oxidized by the carburizing gas, and it is difficult to obtain an effective titanium carbide layer, and it is easy to peel off when an oxide layer is formed on the surface. , Not high hardness. On the other hand, according to this method, when carburizing treatment is performed first, and then titanium is diffused and infiltrated, the surface of the metal material is oxidized, and it is difficult to obtain a uniform titanium layer. Inhibit.

[0008] As described above, there are occasional cases where titanium is diffused and infiltrated into the surface of a metal material, and there is a case where the thickness and hardness of a titanium carbide layer is mentioned as an experimental example. Actually, at present, those applied to corrosion-resistant and wear-resistant parts have not been put to practical use yet. The harder the titanium diffusion layer is, the greater the difference in hardness between the material to be treated and the easier it is to peel off, and simply forming the titanium carbide layer cannot withstand practical use. . An object of the present invention is to provide an iron part further improved in abrasion resistance, corrosion resistance, and peeling resistance even in parts including a part having a complicated shape in view of the current situation.

[0009]

Means for Solving the Problems The present inventors have studied the hardness mHV.
Titanium carbide, which is a super hard compound called 3,300 to 4,000, is hardened with a material hardness of about mHV 250 to 650.
Focusing on the fact that the peel resistance decreases when simply joined to the surface of the part, maintaining the highest hardness part on the outermost surface at a certain thickness, then giving a gentle hardness gradient and titanium concentration gradient,
Pay attention to the fact that titanium carbide is dispersed in the matrix and gradually becomes low in concentration, so that there is no sharp difference in hardness at the boundary with the material to improve the peeling resistance and thus the life of the component body As a result of conducting various experiments, a corrosion-resistant and abrasion-resistant part of the present invention was obtained.

That is, the corrosion-resistant and wear-resistant parts of the present invention are:
A titanium concentration of 45 to 80% by weight and a micro-Vickers hardness m are obtained by subjecting the surface of a component made of an iron material containing at least 0.7% by weight of carbon to diffusion and infiltration of titanium.
Titanium carbide coating layer comprising a hardened portion layer of HV 2,000 to 3,700 and a gradient portion layer having a titanium concentration gradient and a hardness gradient continuously to the boundary with the iron material. And the thickness of the titanium carbide coating layer is set to 10 to 60 μm, and the thickness of the gradient portion layer is set to 30 to 50% of the thickness of the titanium carbide coating layer. .

[0011]

DETAILED DESCRIPTION OF THE INVENTION [I] Raw material (1) Base material In the corrosion-resistant and wear-resistant parts of the present invention, it is important to use as a base material an iron material containing at least 0.7% by weight of carbon as a base material component. It is. Examples of the iron material used as the base material component include high-carbon steel, high-carbon alloy steel, cast iron, cast steel, and the like. Here, the reason why the carbon content in the base material is limited to 0.7% by weight or more is that the carbon component in the titanium carbide coating layer is subjected to carburizing treatment as disclosed in the above-mentioned JP-A-1-177355. Therefore, instead of taking in the coating layer from the outside, the carbon contained in the base material is directly taken in, thereby reducing the processing cost, and the hardened surface hardened layer and the titanium concentration gradient and hardness of the desired thickness are obtained. This is for obtaining a titanium carbide coating layer composed of a gradient portion layer having a gradient portion. That is, in the present invention, the hardened portion layer of the titanium carbide coating layer formed on the surface is formed by bonding titanium diffused from the surface and carbon contained in the base material, and is intended to obtain a desired high hardness coating layer. Requires that the carbon content of the coating layer be 15 to 20% by weight, which is very high, which is tens of times the carbon content contained in the base material. If the carbon content is less than a certain value, the amount of carbon supplied from the base material is insufficient and a desired hard coating layer cannot be obtained.

(2) Titanium carbide coating layer In the present invention, a titanium carbide coating layer is provided on the surface of such an iron material. The titanium carbide coating layer comprises a hardened portion layer on the outermost surface, And a gradient portion layer having a titanium concentration gradient and a hardness gradient portion with a raw material (base material). The gradient layer having the concentration gradient and the hardness gradient can also be referred to as a gradient layer.

(A) Hardened part layer The effective titanium concentration of the hardened part layer having high hardness is 4
If it is less than the above range, the amount of titanium carbide dispersed in the matrix is insufficient to secure the hardness, and if it exceeds the above range, the titanium concentration may be further increased. This is because no change in hardness occurred. The titanium concentration can be measured by analysis using an X-ray microanalyzer.

(B) Gradient section layer Accordingly, in the present invention, the hardness of the titanium carbide coating layer on the surface of the iron material gradually starts to increase from the material boundary, and from the viewpoint of the material (base material), the titanium carbide coating layer It is formed by forming a so-called inclined coating having the highest hardness from about half (30-50%) of the thickness to the outermost surface. According to the experiments by the inventors, this inclined layer has the least peeling when the thickness is 30 to 50% of the thickness of the titanium carbide coating layer, shows a gentle hardness gradient between the material hardness and the highest hardness part, and Since the highest hardness part having a hardness of mHV 2,000 to 3,700 with high wear resistance can be secured, the best result was obtained.

(C) Thickness of titanium carbide coating layer The thickness of the titanium carbide coating layer of the component of the present invention is 10 to 6
When the thickness is less than the above range, the maximum hardness part is extremely thin as about 5 μm, and the peeling resistance can be sufficiently ensured, but the life of the component is not extended satisfactorily. This is because it is difficult to obtain a desired decrease in outermost surface hardness.

[II] Production of Parts (Diffusion Penetration Treatment) In order to produce the parts having excellent corrosion resistance, abrasion resistance and peeling resistance of the present invention by permeation treatment of the above-mentioned parts, the parts usually have a particle size of 200. 60-85 parts by weight of an alloy powder of 70% by weight of titanium and 30% by weight of iron of the mesh were mixed with sinter-alumina powder 1
0 to 25 parts by weight, ammonium chloride powder 0.
After filling into a semi-closed container made of a steel sheet together with a sufficiently enriched mixed powder (hereinafter referred to as a permeating agent) consisting of 1 to 1 part by weight, 900 ppm while flowing an inert gas such as argon gas.
By performing the treatment at １，1,150 ° C. for 8 to 15 hours, the component of the present invention can be obtained. The component subjected to the diffusion and infiltration treatment is cooled after being heated together with the permeating agent in a semi-closed container made of a steel sheet as described above. The part has a gradually cooled structure, which is much lower than the hardness before the treatment, but it is still possible to obtain a part having a sufficient hardness gradient. Vacuum or else return quenching and sintered under an inert atmosphere, a special case, i.e., in the parts where large particles very large impact load such as collision at a high speed is placed under such environmental coating layer of the surface The material portion softened immediately below the coating layer before being completely worn out is deformed by the impact, so that the titanium carbide coating layer peels off and falls off, and the wear resistance of the titanium carbide coating layer may not be able to exhibit 100%. Sometimes. In view of the above, even in such an environment, it is intended to make the component capable of fully exhibiting the wear resistance of the coating layer. After forming the titanium carbide coating layer, the component is placed in a vacuum or in an inert atmosphere. By performing quenching and tempering in the inside, as shown in FIG. 2, the material softened portion immediately below the titanium carbide coating layer is eliminated, the hardness of the material is significantly increased, and the difference in hardness between the titanium carbide coating layer and the material portion is small, and Thus, it is possible to obtain the product of the present invention in which the hardness gradient in the titanium carbide coating layer is more gentle. Such a product can exhibit excellent corrosion resistance and abrasion resistance without peeling or falling off of the coating layer even in a use environment in which an impact load is particularly large.

[III] Corrosion- and wear-resistant parts The hardened part layer of the present invention thus obtained, and a gradient part layer having a titanium concentration gradient and a hardness gradient continuously up to the boundary with the iron material. The titanium carbide coating layer composed of and has excellent corrosion resistance, abrasion resistance, and peeling resistance. In normal cases, the titanium carbide coating layer can sufficiently withstand use.

[0018]

By providing the parts of the present invention, the coating layer maintains corrosion resistance and abrasion resistance for a long time even when used under severe corrosion and abrasion environments which could not withstand the conventional use, and as a part without peeling. Functions can be performed stably.

[0019]

[Example 1] Ten test pieces (containing 1.05% by weight of carbon) made of SUJ-2, a high carbon chromium bearing steel of 60φ × 10t, were prepared by using 70% Ti / 30% Fe with a particle size of 200 mesh. 70 parts by weight of titanium-iron alloy powder consisting of sinter-alumina powder 15
It was embedded together with a permeating agent consisting of 0.5 parts by weight of ammonium chloride powder and subjected to diffusion permeation treatment at 1100 ° C. for 12 hours while flowing argon gas. Five of them were subjected to oil quenching at 1,080 ° C. using a vacuum quenching / tempering device, and then tempered at 230 ° C. to obtain a titanium carbide coating layer having a thickness of 45 μm according to the present invention. Was.

A test piece which was not subjected to vacuum quenching and tempering and a test piece which had been subjected to cutting and polishing were cut and polished, and the hardness distribution of the cross section is shown in FIG. FIG. 3 shows the analysis result of the implemented piece cross section by an X-ray microanalyzer, and FIG. 4 shows the optical microscope structure. In FIG. 2, 1 indicates a test piece subjected to quenching / tempering processing, 2 indicates a test piece not subjected to such processing, and 11 in FIG.
Indicates a titanium carbide coating layer, and 12 indicates an iron material portion. As is apparent from FIGS. 2 and 3, the thickness of the surface hardened portion layer is 25.
The maximum hardness is 32 μm after quenching and tempering.
50 mHV, those not performed were 3120 mHV, and the thickness of the gradient layer was 20 μm. The hardness of the material part was mHV2 which had not been quenched and tempered.
20 compared to mHV755 and 3
More than doubled. Therefore, the hardness gradient from the hardened portion layer to the material is gentler, and it can be seen that the wear resistance and the peeling resistance are further improved.

In order to compare the abrasion resistance, one of each of the remaining four sheets was used, the nozzle diameter was 9 mm, the projection material was 150 mesh conical silica sand, the projection pressure was 1 kg / cm ² , the projection speed was 36 m / sec, and the projection was performed. When a quartz sand blasting test was performed for 48 hours at an angle of 80 °, both of them showed a thickness reduction due to abrasion of about 8 to 10 μm, but there was no peeling and a sound layer remained.

At the same time, the same material was subjected to a test using a test piece having a thermal spray layer thickness of 450 to 500 μm formed by WC-Co thermal spraying. As a result, the coating layer was peeled and dropped over a wider area than the portion where the silica sand was projected. At the projected portion, the abrasion reached the inside of the material, and when the depth thereof was measured by a fine surface roughness meter, it reached 2.184 mm. Similarly, when a test was performed using an untreated test piece,
After a lapse of time, the wear depth reached about 4 mm, so the test was discontinued halfway.
Peeling resistance could be confirmed. Further, as a result of performing a salt spray test at 35 ° C. specified in JIS Z2371 for 168 hours using the test piece of the present invention, the weight loss due to corrosion was extremely low at 0.32 to 0.35 mg / cm ² , respectively.
It showed excellent corrosion resistance. Example 2 A pump impeller made of gray cast iron FC20 having a diameter of 250φ (containing 3.35% of carbon) was added to the mixed powder used in Example 1, and 0.5 part by weight of ammonium chloride powder was newly added. It was buried in a semi-hermetic container made of steel plate together with a permeating agent, and was subjected to diffusion permeation treatment at 900 ° C. for 10 hours while flowing argon gas to obtain a treated part of the present invention having a titanium carbide coating layer 45 μm. The thickness of the surface hardened portion layer was 27 μm, the titanium concentration was 76% by weight, the maximum hardness was mVH3025, and the thickness of the gradient portion layer was 18 μm.

When the pump impeller was attached to a 175 ° C. molten calcium chloride transport pump and used at 1,300 RPM for three months, rust was found in some parts, but no damage was found in other parts. I couldn't. The flow rate of the conventional untreated FC20 pump impeller, which was used in parallel, decreased after one month, so it was confirmed that the pump impeller was taken out. The thickness was 1 mm or less, and the corrosion resistance and wear resistance of the component of the present invention could be confirmed.

[0024]

According to the present invention, it is possible to provide a long-life component having high corrosion resistance, abrasion resistance, and peeling resistance even in a severe corrosive and abrasion environment, and it is not necessary to replace components and to increase the cost. By enabling stable operations, it has made it possible to improve productivity and reduce costs.

[Brief description of the drawings]

1A and 1B are diagrams showing an example of a pump impeller, in which FIG. 1A is a sectional view and FIG. 1B is a plan view.

FIG. 2 is a graph showing a hardness distribution of a cross section of the product obtained in Example 1.

FIG. 3 is a graph showing an analysis result of titanium of the product obtained in Example 1 by an X-ray microanalyzer.

FIG. 4 is a sketch diagram showing an optical microscope structure of the product obtained in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump impeller 3 Opening 4 Opening 7 Cavity

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Tsuji 376-10 Naganoura, Togitsuda-Kururigo, Nishisonogi-gun, Nagasaki Pref. No. 6-14 Maruo, Nagasaki Works, Mitsubishi Electric Corporation (56) References JP-A-52-46339 (JP, A) JP-A-2-254149 (JP, A) JP-A-4-293765 (JP, A )

Claims (2)

(57) [Claims] An iron material containing at least 0.7% by weight of carbon
The surface of the component made of, this for diffusing osmotic process titanium
And a titanium concentration of 45 to 80 wt%, lifting the hardened layer of the micro-Vickers hardness MHV2,000～3,700, therewith a gradient and hardness gradient of titanium continuously up to the boundary between the iron material Composed of two gradient sections
Subjecting titanium carbide coating layer is, the Chitanka
The thickness of the Baito coating layer is 10 to 60 [mu] m, the thickness of the gradient layer of the thickness of the titanium carbide coating layer 30-5
Corrosion-resistant and wear-resistant parts characterized by being 0%. 2. The corrosion-resistant and abrasion-resistant part according to claim 1, wherein the part is quenched and tempered in a vacuum or in an inert atmosphere after the diffusion and infiltration treatment.