JPH1112758A - Metallic parts coated with cermet sintered compact, and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating layer minimal in the occurrence of falling as well as cracking due to external force by forming a cermet sintered compact layer on the surface of a base material composed of ferrous metal and also forming an intermetallic layer where Fe is allowed to diffuse so that it has a concentration gradient toward the cermet sintered compact layer side. SOLUTION: A cermet sintered compact layer 1, which consists of a ceramic phase composed essentially of a compound boride of Ni and Mo and/or W and a metallic binding phase composed essentially of Ni and containing Mo, is formed via an intermetallic layer 3 on the surface of a base material 2 composed of ferrous metal. The intermetallic layer 3 is composed essentially of Ni, Fe and Mo, where Mo is allowed to diffuse from the cermet sintered compact layer 1 toward the ferrous metallic base material side and further Fe is allowed to diffuse, having a concentration gradient, from the ferrous metallic base material toward the cermet sintered compact layer side. The ceramic phase is contained by 30 to 70 wt.% in the cermet sintered compact layer, and >=85 wt.% of the ceramic phase is composed of a compound boride of Ni and Mo and/or W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cermet-coated metal part coated with a cermet sintered body, having heat resistance, abrasion resistance, corrosion resistance and impact resistance and having good workability, and a method for producing the same. .

[0002]

2. Description of the Related Art Various attempts have been made to coat a metal or a steel base material with various alloys or ceramics to impart heat resistance, wear resistance and corrosion resistance. The so-called nitriding treatment is a typical method of forming a film by reacting the surface of a heated metal with a gas, a metal salt, or the like, and has been used for a long time. However, the types of films that can be coated by such a method are limited, and it is difficult to obtain denseness of the film, so that the effect is limited.

For this reason, a physical or chemical vapor deposition method (PVD method or CVD method) has been proposed as a means for forming a relatively wide variety of films and obtaining a dense film.
In recent years, metal surface modification by these methods has been widely performed. However, the thickness of a film that can be formed by PVD or CVD is only a few μm at the maximum, and the adhesion of the film is low because there is no metallurgical reaction between the film and the metal base material. Therefore, the effect cannot be expected to be maintained under severe use conditions, that is, when an excessive load or mechanical or thermal shock is applied to the coated surface.

[0004] There is a thermal spraying method as a method for forming a wide variety of films from various alloys to ceramics having an extremely high melting point. The thermal spraying method is a method in which mainly powders of metals and ceramics are supplied and melted in a high-temperature flame, and at the same time, the molten material is beaten to a base material by a high-pressure gas to form a film. There are many types depending on the type. According to some types, a film having a thickness of several mm can be obtained. However, in general, to increase the effect of the coating, it is necessary to spray a material that has properties greatly different from the base metal, and it is extremely difficult to increase the thickness of the coating when spraying this type of coating. It is.

One of the metal surface coating methods that has been practiced for a long time is a cladding method. This build-up method is a method in which the raw material to be formed into a film is melted on the surface of the base material and integrated with the base material. According to this method, it is relatively easy to make the film thicker and the adhesion of the film is also improved. High enough. However, the range of materials that can be overlaid is limited, and only a few alloys are industrially established.

[0006]

In order to dramatically improve heat resistance, wear resistance and corrosion resistance while forming a film on the metal surface and maintaining the mechanical and thermal shock resistance of the metal, ,
A coating containing a large amount of ceramics, whose heat resistance and hardness are much higher than that of metal, must be sufficiently thick and firmly adhered to the metal surface. However, nitriding, P
VD, CVD, thermal spraying and overlaying are basically not methods that can form a film satisfying this condition. Therefore, one of the methods that may satisfy this requirement is capsule H
A film forming method by IP (hot isostatic pressing) processing has been proposed.

[0007] The film formation by the capsule HIP process can be performed as follows. First, a space for filling the raw material powder on the surface of the base material on which the film is formed is prepared, and after the raw material is filled, degassing is performed. Thereafter, the whole is loaded into a HIP device, and the powder is sintered by applying a high temperature and a high pressure, and at the same time, is brought into close contact with the surface of the base material. The type of the raw material and the thickness of the space filled with the raw material can be freely changed, and it can be expected that the sintered body of the film and the base material are firmly adhered by the action of high temperature and high pressure. In order to make use of the superiority of this method, attempts have been made to form a film by a capsule HIP treatment of various ceramics or a composite material (cermet) with a metal mainly composed of ceramics.

However, since the thermal and mechanical properties of ceramics and cermets are significantly different from those of the base metal, a firmly adhered film is easily cracked by a change in temperature or a load of mechanical stress. Or peel off. In order to prevent such cracking and peeling, it is effective to interpose a soft metal layer having a sufficient thickness between the ceramic or cermet film and the base material. However, since a thick and soft layer is easily deformed when subjected to a large external load, this means of improvement cannot be adopted in a mold or the like that needs to maintain a precise shape.

As a result, it is possible to dramatically improve heat resistance, abrasion resistance, and corrosion resistance while maintaining the mechanical and thermal shock resistance of the metal. There are many difficulties in obtaining a coated metal part in which a coating containing a large amount is firmly adhered by capsule HIP processing.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made to solve these problems, and a composite boride of Ni, Mo and / or W (namely, Ni And Mo double borides, Ni and W double borides and Ni
A cermet sintered body layer composed of a ceramic phase mainly composed of at least one selected from double borides of Mo and W) and a metal bonded phase mainly composed of Ni containing Mo; An intermediate layer mainly composed of Ni, Fe, and Mo in which Mo is diffused into the Fe-based metal base material and Fe is diffused from the Fe-based metal base material to the cermet sintered body layer side with a concentration gradient; The present invention provides a metal part coated with a cermet sintered body, wherein a metal part is formed.

A ceramic powder mainly composed of a composite boride of Ni, Mo and / or W or a composite powder composed of a powder having a composition capable of producing the ceramic and a metal powder mainly composed of Ni and Mo is coated. A space provided on the surface of an Fe-based metal base material to be filled, the inside of the space being evacuated, and then subjected to hot isostatic pressing (HIP) treatment. Provided is a method for manufacturing a part.

Cermet sintered bodies (hereinafter also simply referred to as cermets) composed of a ceramic phase mainly composed of a composite boride of Ni, Mo and / or W and a metal binding phase mainly composed of Ni are used in various fields of application. Is a material that can be used in place of cemented carbide, and is excellent in heat resistance, abrasion resistance, corrosion resistance and impact resistance.

The hardness and strength of this cermet at a high temperature are sufficiently higher than those of surface coating alloys such as Ni-based self-fluxing alloys and Co-based superalloys, and its thermal expansion coefficient is higher than that of ceramics and cemented carbides. Close to metal. For this reason, if a film made of the cermet is formed on a metal material such as a steel material, it is expected that a hard metal component having excellent heat resistance and corrosion resistance can be formed. However, if the coating layer of the cermet is formed directly on a metal material such as a steel material as a base material, cracks are likely to occur at the interface between the cermet layer and the base material when an impact force is applied. Easily peels off.

In the present invention, as schematically shown in FIG. 1, the intermediate layer 3 formed by reacting the component of the cermet layer 1 with the Fe-based metal layer 2 serving as the base material is used to form the intermediate layer 3 between the cermet layer and the metal base material. Since the intermediate layer is formed between the two layers, the intermediate layer functions as a buffer layer for gradually adjusting the matching and the characteristic difference between the crystal lattices of the two materials, thereby preventing the cermet layer from peeling off. However, in order for the intermediate layer 3 to sufficiently exhibit the effect as a buffer layer, it is important that the intermediate layer itself has a gradient composition.

That is, in the intermediate layer 3 in the coated metal part according to the present invention, as shown in FIGS. 1 and 2, the content of Fe decreases proportionally from the base metal layer 2 side to the cermet layer 1 side. It is desirable to have a concentration gradient that is
Also, as shown in FIG. 2A, it is preferable that the Mo content is gradually increased in the cermet layer side.
As in the case of the Ni content shown in (b), there is no need to have a concentration gradient especially in the entire intermediate layer, and there is no problem even if the concentration changes abruptly as compared with Fe. Such a cermet-coated metal part having a cermet layer and an intermediate layer can be formed by a surface coating method using a capsule HIP process in which heating conditions are accurately controlled, and when the size and shape of the base material change. Cannot be realized by the thermal spraying method or the overlay method in which it is difficult to strictly control the heat input.

In the present invention, any Fe-based metal base material may be used as long as it contains Fe as a main component, and various stainless steels, carbon steels, alloy steels and the like can be used in general. Note that materials such as alloy tool steel and high-speed steel that are easily cracked by heat treatment are not preferable.

In the present invention, 85% by weight or more of the ceramic phase constituting the cermet layer is preferably a composite boride of Ni, Mo and / or W. If the amount is less than 85% by weight, the heat resistance of the cermet layer is reduced, and the cermet layer is likely to be deformed or dropped off when exposed to a high temperature.

In the cermet layer component of the coated metal part of the present invention, the ceramic phase preferably accounts for 30 to 70% by weight, particularly 40 to 60% by weight. If the amount of the ceramic phase is less than 30% by weight, the excellent properties of the composite boride cannot be imparted to the cermet layer, and the hardness and high-temperature strength may decrease. If the amount of the ceramic phase exceeds 70% by weight, the impact resistance of the cermet layer is reduced, and cracks are easily generated in the cermet layer.

Further, 60% by weight or more, particularly 65% by weight or more of the components of the metal binder phase constituting the cermet layer,
Is preferably Ni. 6 Ni in the metal binding phase
When the content is 0% by weight or more, the formation of the third phase imparting undesired properties can be suppressed, and when the content is 65% by weight or more, a build-up layer stably exhibiting excellent properties can be obtained.

It is necessary that Mo is contained in the metal binding phase of the cermet layer.
It is preferably at least 15% by weight, especially at least 15% by weight. When Mo is dissolved in the metal binding phase by 12% by weight or more, diffusion at the interface between the cermet coating and the base metal is promoted, and the formation of a preferable intermediate layer is controlled. On the other hand, the upper limit of the amount of Mo dissolved in the metal binding phase is determined by the maximum metallurgical solid solution of Mo in the entire metal phase.

The preferred material of the cermet layer of the coated metal component of the present invention, more than 70 wt% of the ceramic phase is Mo _X Ni _Y B ₂ or _{(Mo, W) X Ni Y} B 2
(Where X is 1.8 to 2.2 and Y is 0.9 to 1.1), and 60% by weight or more of the metal binding phase is Ni. When the composition of the cermet layer is within the range represented by X and Y, the X-ray diffraction pattern of the cermet layer hardly changes. Mo _X Ni _Y B ₂ and (Mo, W) _X N
i _Y B ₂ is a very high ceramic bond strength between the Ni-based metal phase, these phases of ceramic 70 wt% or more, the strength of the cermet sintered body by more preferably contains more than 75 wt% Stable and high.

[0022] In the coated metal part of the present invention, the thickness of the cermet layer is preferably 1.0 to 5.0 mm. By setting the thickness of the cermet layer to 1.0 mm or more, preferable characteristics of the cermet are imparted to the build-up layer. However, increasing the thickness beyond 5.0 mm is difficult in terms of capsule design and cost, which is not preferable in terms of cost. Further, the thickness of the intermediate layer is preferably from 0.01 to 0.2 mm. The thickness of the intermediate layer is 0.01 to 0.2 mm
By doing so, excellent adhesion can be obtained. More preferably, the thickness of the cermet layer is 1.5 to 4.0 mm,
A more preferred thickness of the intermediate layer is 0.02 to 0.1 mm.

In the present invention, the intermediate layer is an alloy layer composed of Fe, Mo, and Ni diffused from the Fe-based metal base material and the cermet layer. In many cases, it is in a state of having been done.

The cermet-coated metal part of the present invention can be obtained as follows. Slurry obtained by weighing boride powders such as MoB and WB and metal powders such as Mo and Ni and mixing and pulverizing them in an organic solvent such as ethanol using a rotary ball mill or an attrition mill. Dry under reduced pressure and use this as a raw material for capsule HIP.

The raw material powder used here does not need to be a combination of a boride powder and a metal powder as described above. For example, a combination of a Ni—B alloy with Mo powder and W powder, or an atomizing method or another method A combination of a composite boride powder synthesized with the above and a metal powder, or a combination of a single metal powder such as Ni, Mo, W or the like and a B powder may be used. Generally, these raw material powders are as pure as possible, and the finer the powder, the more advantageous it is in obtaining a coating layer having excellent properties. In particular, in order to ensure the uniformity of the coating layer to be formed, the average particle size of the boride powder is preferably set to 10 μm or less.

The raw material powder obtained by the above-described method is filled in a space provided on the surface side of the metal base material to be coated. The thickness of this space needs to be set based on the thickness of the coating layer to be obtained as a result, and the filling rate of the raw material powder is desirably as high as possible, and is usually 50% or more. Next, the inside of the layer filled with the raw material powder is evacuated and evacuated. In order to enhance the characteristics of the resulting coating layer, the ultimate degree of vacuum by this evacuation is preferably as high as possible, and the pressure is preferably 1 × 10 ⁻³ Torr or less. In addition, in the vacuuming step, it is effective to perform heating for removing adsorbed moisture and the like from the raw material powder packed bed. After sealing the evacuated raw material filling chamber, it is subjected to capsule HIP processing.

The HIP treatment for obtaining the cermet-coated metal part of the present invention is performed using an argon gas or the like as a pressurized medium. The maximum temperature during the treatment is preferably 1050 to
The temperature is 1250 ° C., more preferably 1100 to 1200 ° C., and the temperature is maintained for 1 to 5 hours. The pressure to be applied is preferably 800 to 1800 atm, more preferably 1200 to 1600 atm. If these temperatures and pressures are too low, sufficient mechanical properties of the cermet layer and strong adhesion between the coating layer and the base material cannot be obtained. Conversely, if the temperature and pressure are too high, fragile reactions occur at the interface between the coating layer and the base material. Layers come into being.

[0028]

EXAMPLES Examples of the present invention (Examples 1 to 8) and comparative examples (Examples 9 to 12) will be described below, but the present invention is not limited thereto.

(Example 1) MoB powder (purity: about 99.5% by weight, average particle size: 4 μm) 40% by weight, WB powder (purity: 9
9.6% by weight, average particle size 3 μm) 3% by weight, Mo powder (purity about 99.8% weight%, average particle size 7 μm) 9% by weight
And Ni powder (purity: about 99.6% by weight, average particle size: 10μ)
m) A raw material consisting of 48% by weight was subjected to mixing, pulverizing and drying steps to obtain an alloy powder for capsule HIP.

This alloy powder was converted to chromium molybdenum steel (S
CM440) After filling the space between the cylinder and the carbon steel outer cylinder arranged outside thereof and sealing it by vacuum, the maximum temperature is 1120 ° C.
HIP under the conditions of a holding time of 3 hours and a pressure of 1500 atm.
Processing was performed. After the HIP treatment, the inner and outer diameters and the like were processed to produce a cermet-coated sleeve for die casting shown in FIG. The thickness of the coating layer of this sleeve is about 3
mm.

The cermet-coated sleeve was cut at several points perpendicular to the longitudinal direction and the section was observed with a metallographic microscope. The thickness of the cermet layer was about 2.8 to 3.2 mm. The thickness of the intermediate layer formed between them was about 0.02-0.03 mm. When the compositions of the coated cermet layer and the intermediate layer were analyzed using a wet extraction method, qualitative X-ray analysis, and an X-ray microanalyzer, the results were as follows.

Cermet layer Ceramic phase ratio: 54% by weight, Ceramic phase state: Mo ₂ NiB ₂ and (Mo,
W) ₂ NiB ₂ , ratio of metal binding phase: 46% by weight, state of metal binding phase: Ni—Mo alloy phase (Ni: 80% by weight, Mo: 17% by weight).

-Intermediate layer The main component is an Fe-Ni alloy, and Mo is dissolved in a solid solution. As schematically shown in FIG. 2, these three components each show a concentration gradient in the layer. In particular, Fe has a concentration gradient that decreases almost linearly from the metal base material side to the cermet side. Quantifying these components at about the center of the middle layer,
Ni: about 37%, Fe: 52%, Mo: 8%.

This sleeve is made of Al having a melting temperature of 680 ° C.
When a test was performed using an aluminum die-casting injection sleeve for forming a die-casting alloy (ADC12 alloy), 460,000 moldings could be performed before a part of the coating layer was peeled off and became unusable. The molding test was 6.6 times that in the case of using an injection sleeve (nitrided product) made of alloy tool steel (SKD61).

(Examples 2 to 8) The same MoB as used in Example 1
Using WB, Mo and Ni powders and various additional raw materials (all having a purity of 99% or more and an average particle size of 8 μm or less),
A raw material for P was produced. Capsule HIP using this raw material
After performing the treatment, the same die casting injection sleeve as that manufactured in Example 1 was manufactured and subjected to a molding test performed under the same conditions as in Example 1. The results are shown in Tables 1 and 2.

(Examples 9 to 12) The same tests as those performed in Examples 1 to 8 were carried out using various composite die-casting sleeves (in which a high corrosion-resistant material was provided by surface treatment or shrink fitting on the inner surface into which an aluminum melt enters). Table 3 shows the results.

In the method of shrink-fitting a high corrosion resistant material layer material as in Examples 9 and 10, since there is no intermediate layer serving as a buffer layer, cracks are likely to occur due to uneven processing accuracy and uneven temperature during molding. On the other hand, in the case of Examples 11 and 12 in which a metal-based material is used as the high corrosion-resistant material,
It is easy to apply a manufacturing method capable of forming an intermediate buffer layer. However, the corrosion resistance of stellite and Ti-based composite materials to molten aluminum is inferior to that of the cermet coating layer provided by the present invention, and the number of moldable shapes does not significantly exceed that of alloy tool rigid sleeves.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

The cermet-sintered metal part of the present invention comprises a ceramic phase mainly composed of a composite boride of Ni and Mo and / or W and a metal-bound phase mainly composed of Ni containing Mo. Mo diffuses from the body layer and the cermet sintered body layer to the Fe-based metal base material side,
The coating layer in which an intermediate layer mainly composed of Ni, Fe, and Mo in which Fe is diffused with a concentration gradient from the e-base metal base material to the cermet sintered body layer side is formed is an injection sleeve for die casting. It is denser and has a sufficient thickness compared to the nitrided layer of iron and steel materials that are frequently used for etc.It is widely used for Co-based alloys such as stellite which is often overlaid for the same application, mechanical seals and pump sleeves Compared to the build-up layer of a Ni-Cr-B self-fluxing alloy that has a low content of B and is not a cermet, it has significantly higher high-temperature strength and hardness, and is inferior in adhesion, corrosion resistance and thermal shock resistance. Absent.

Furthermore, the adhesion of the coating layer comprising the cermet layer and the intermediate layer formed by the reaction of the component of the cermet layer with the metal base material of the cermet-coated metal part of the present invention is such that only the cermet layer formed by the thermal spraying method is used. Remarkably greater than the adhesion of a film consisting of Further, as compared with a layer in which a ceramic sintered body is mechanically combined with a metal member, the coating layer provided by the present invention is extremely unlikely to be cracked or fall off due to an external force.

Therefore, the coating provided by the present invention can be applied to metal parts having various shapes and various sizes. For this reason, the cermet-coated metal parts according to the present invention are not only required to have corrosion resistance and strength as represented by an injection sleeve for aluminum die casting, but also used in applications where thermal and / or mechanical impact force is repeatedly applied. Shows excellent service life and greatly improves the cost performance of these devices. In addition, the cermet-coated metal part of the present invention has high wear resistance and excellent slidability, and is expected to bring about a great improvement effect by reducing product quality and cost in a wider range of applications.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically illustrating a metal part coated with a cermet sintered body according to the present invention.

FIG. 2 is an explanatory diagram showing a change in component composition of an intermediate layer formed between a cermet sintered body layer and a metal base material in the present invention.

FIG. 3 is a view for explaining an example and a comparative example of the present invention, and is a schematic view of an injection sleeve for die casting.

[Explanation of symbols]

 1: coated cermet layer 2: base metal 3: intermediate layer

Claims (8)

[Claims] 1. A ceramic phase mainly composed of a composite boride of Ni and Mo and / or W is formed on a surface of an Fe-based metal base material.
a cermet sintered body layer composed of a metal binding phase mainly composed of Ni containing o, Mo diffuses from the cermet sintered body layer to the Fe-based metal base material side, and further, the cermet sintered body is formed from the Fe-based metal base material. A metal part coated with a cermet sintered body, characterized in that an intermediate layer mainly composed of Ni, Fe and Mo in which Fe is diffused with a concentration gradient is formed on the layer side. 2. The metal part coated with a cermet sintered body according to claim 1, wherein the ceramic phase is contained in the cermet sintered body layer in an amount of 30 to 70% by weight. (3) at least 85% by weight of the ceramic phase is
The metal part coated with a cermet sintered body according to claim 1 or 2, which is a composite boride of Ni, Mo and / or W. 4. A ceramic phase comprising at least 70% by weight of M
o _X Ni _Y B ₂ or _{(Mo, W) X Ni Y} B 2 ( where X is 1.8 to 2.2, Y 0.9 to 1.1), and 60 wt% of said metal binder phase The cermet sintered body-coated metal part according to claim 1, wherein the metal part is Ni. 5. The metal part coated with a cermet sintered body according to claim 1, wherein at least 12% by weight of said metal binder phase is Mo. 6. The cermet sintered body layer has a thickness of 1.0 to 1.0.
5.0 mm, and the thickness of the intermediate layer is 0.01 to 0.5 mm.
The cermet sintered body-coated metal part according to claim 1, 2, 3, 4, or 5, which has a diameter of 2 mm. 7. A ceramic powder mainly composed of a composite boride of Ni, Mo and / or W or a composite powder composed of a metal powder mainly composed of Ni and Mo and a powder having a composition capable of producing said ceramic. 4. A hot isostatic press (HIP) process after filling a space provided on the surface of the Fe-based metal base material to be formed, evacuating the inside of the space, and performing a hot isostatic pressing (HIP) process. 7. The method for producing a metal part coated with a cermet sintered body according to 4, 5, 5 or 6. 8. The maximum temperature of the HIP processing is 1050 to 125.
The method for producing a metal part coated with a cermet sintered body according to claim 7, wherein the temperature is 0 ° C and the pressure of the HIP treatment is 800 to 1800 atm.