JP3134768B2 - Boride cermet spraying powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a thermal spray coating layer of tungsten carbide cobalt (WC-Co), which is a typical thermal spraying cermet material, and a chromium carbide nickel chromium (WC) alloy. Cr ₃ C
_2- NiCr) -based thermal spray coating layer having heat resistance and oxidation resistance superior to those of the WC-Co-based and Cr ₃ -based thermal spray coating layers.
The present invention relates to a thermal spray powder for producing a cermet thermal spray coating having high thermal shock resistance and toughness not found in a C ₂ -NiCr spray coating.

[0002]

2. Description of the Related Art In recent years, with the advancement of industrial machinery, etc., with the advancement of high performance, high precision, diversification, and low energy cost, the use of materials containing metals and ceramics as components for thermal spraying has been increasing. The required performance of a cermet sprayed coating layer which forms a cermet coating by using the cermet coating has become more and more strict, and a higher performance is required than ever before. Conventionally, a typical cermet spray coating layer (hereinafter, also simply referred to as a coating layer or a spray coating) varies depending on the use temperature and ranges from room temperature to 50.
In the temperature range up to about 0 ° C, WC-Co and WC-N
In the high temperature range up to 900 ° C., which is higher than this, there are Cr ₃ C ₂ —NiCr type and Cr ₃ C ₂ —Ni type, and these coating layers have the hardness according to the purpose, It has heat resistance, abrasion resistance, oxidation resistance and the like.

However, as described above, as the use environment of cermets becomes more diversified with the recent industrial development, it is desired to further improve these characteristics. The development of a coating material having both properties and toughness is desired. For example, it is immersed in a high-temperature hot-dip galvanizing bath (450 to 500 ° C.) or molten aluminum (700 to 800 ° C.) for manufacturing a surface-treated steel sheet for an automobile or the like, and continuously passed. A sink roll used to support and guide the steel sheet and apply a uniform galvanization to the surface of the steel sheet,
A coating layer for covering a support roll or the like is required to have not only high hardness, simple heat resistance and abrasion resistance but also corrosion resistance to molten metal, thermal shock resistance and excellent toughness.

[0004] Among the conventional cermet coatings described above,
In a dry atmosphere up to 500 ° C., the WC-Co type has excellent hardness and abrasion resistance, but has low corrosion resistance and heat resistance. In particular, there is a problem in heat resistance and corrosion resistance in an oxidizing atmosphere at 500 ° C. or higher. is there. Also, Cr ₃ C ₂ —NiCr
In the system, corrosion resistance, heat resistance, and oxidation resistance are maintained up to a high temperature range of 900 ° C., but hardness and wear resistance are inferior. Further, these coatings generally have low thermal shock resistance and poor toughness, so that the coating layer is easily peeled off, and the range of application is limited.

[0005] As described above, conventionally used coatings are:
Even if it is high hardness and excellent wear resistance, corrosion resistance and heat resistance are inferior, even if heat resistance and corrosion resistance are excellent, wear resistance and hardness are insufficient, and in addition, all have thermal shock resistance At present, a cermet sprayed coating that is low and has poor toughness and can simultaneously satisfy all of these required properties has not been obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional cermet sprayed coating, and has high hardness, excellent wear resistance, corrosion resistance, heat resistance, and thermal shock resistance. It is an object of the present invention to provide a thermal spraying powder for forming a cermet sprayed coating having both properties and toughness.

[0007]

Means for Solving the Problems According to the present invention, as a result of intensive studies to solve the above-mentioned problems, the W-Co-based double boride represented by W ₂ CoB ₂ has high hardness and wear resistance. In addition to exhibiting excellent thermal shock resistance and toughness, a cermet is formed by combining the double boride with a Co-Cr-Mo alloy phase having excellent heat resistance as a metal binding phase. Thus, it has been found that a cermet sprayed coating having high hardness and abrasion resistance and having both heat resistance, oxidation resistance and thermal shock resistance can be obtained. In addition, in order to form an appropriate amount of the double boride phase in the cermet film in a dense and uniform dispersion, there is an optimum addition range for B to be contained, and Co, Cr and Mo serving as the metal binding phases are It has been found that it is appropriate to add each as a simple metal, not in the state of an alloy.

[0008] That is, the present invention relates to B2.5
~ 4.0%, Co 15.0 ~ 30.0%, Cr 5.0 ~
It is a boride-based cermet thermal spray powder comprising a composite powder composition containing 10.0%, Mo 3.0 to 6.0%, and the balance W and unavoidable impurities.

The preferred particle size of the powder constituting the thermal spraying powder varies depending on the thermal spraying method. However, when air or reduced pressure plasma thermal spraying is employed, the particle size is preferably 15 to 53 μm.
Is appropriate, and in the case of high-speed gas flame spraying, it is preferably in the range of 5 to 45 μm or 15 to 53 μm. In the composite powder composition, the total of W and B is 52.5 to 70.0% by weight, and Co and Cr
And Mo are preferably in the range of 25.0 to 45.0%.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The components of the cermet spraying powder for obtaining the boride-based cermet spray coating according to the present invention are as described above, and the reasons for limiting the respective components will be described below.

B is an element necessary for forming a double boride phase by combining with W and Co. If the content of B in the cermet spraying powder is less than 2.5% by weight, thermal spray coating is required. The amount of B in the thermal spray coating layer is 1.5
Since the content of the thermal spray coating layer is reduced to less than 10% by weight, sufficient hardness and abrasion resistance cannot be obtained in the obtained thermal spray coating layer. On the other hand, if it exceeds 4.0% by weight, the hardness is increased but the strength (toughness and thermal shock resistance) of the thermal spray coating layer is significantly reduced. Therefore, the B content in the thermal spraying powder is suitably in the range of 2.5 to 4.0%.

W is an element necessary for forming a double boride phase like B, and the double boride phase is W ₂ CoB ₂
Where the content of W in the cermet sprayed powder is 5
If the amount is less than 0.0% by weight, the formation of the double boride phase becomes insufficient, and the sprayed coating layer cannot obtain desired hardness and wear resistance. On the other hand, if it exceeds 70.0% by weight, hardness, abrasion resistance and corrosion resistance to molten zinc and molten aluminum are improved, but toughness, thermal shock resistance and thermal spray adhesion efficiency of powder (yield during thermal spraying) are significantly reduced. . Therefore, the content of W in the thermal spraying powder is appropriately in the range of 50.0 to 70.0%.

[0013] Co is an element that is the main component of the formation of the metal bonding phase, but is also an element that is indispensable for the formation of the double boride phase. The obtained thermal spray coating layer has high temperature strength and oxidation resistance. It has the effect of giving. If the content of Co is less than 15.0% by weight, the amount of mutual solid solution between the formed metal binding phase and the double boride phase is reduced, so that the bonding strength is reduced and defects such as pores are easily generated. Become. On the other hand, 30.0% by weight
If it exceeds, the corrosion resistance of the metal bonding phase is reduced, and fragile borides such as CoB are formed in large amounts in the double borides, so that the toughness of the thermal spray coating layer is reduced. Therefore, the Co content in the thermal spray powder is 1
A range of 5.0 to 30.0% by weight is appropriate.

Cr is an element that contributes to corrosion resistance, heat resistance, and oxidation resistance, and has an effect of forming a metal bonding phase by combining with Co to improve toughness. Cr content is 5.
If the amount is less than 0% by weight, the above effects cannot be sufficiently obtained. If the amount exceeds 10.0% by weight, the corrosion resistance, heat resistance and oxidation resistance of the obtained sprayed coating layer are further improved but the toughness is lowered. Is not preferred. Therefore,
Cr content in the thermal spraying powder is 5.0 to 10.0% by weight.
Is appropriate.

Mo is composed of Co and Cr forming a metal binding phase.
Is an element necessary for further increasing the corrosion resistance and strength of the metal binding phase and forming a double boride represented by Mo ₂ CoB ₂ . If the Mo content is less than 3.0% by weight, the above-mentioned effects cannot be obtained. If the Mo content exceeds 6.0% by weight, the strength of the metal binding phase is rather reduced. Therefore, the W content in the thermal spray powder is:
A range of 3.0 to 6.0% by weight is appropriate.

In the thermal spraying powder composition of the present invention, the total amount of W and B is set to 52.5 to 70.0% by weight, and the total amount of Co, Cr and Mo is set to 25.0 to 25.0% by weight. 4
By regulating the content to 5.0% by weight, embrittlement and peeling phenomena of the obtained thermal spray coating layer can be suppressed. When producing the thermal spraying powder of the present invention, Co, C
It is important to use r and Mo respectively as a single metal powder. This is because when these elements are used in the form of an alloy powder, for example, in the form of a stellite alloy powder or the like, Co in the alloy powder is unlikely to combine with borides such as WB,
This is because W ₂ CoB ₂ double boride is not easily formed.

As a method for cermet spray coating on a substrate using the thermal spray powder of the present invention, a conventional method, that is, an atmospheric or reduced pressure plasma spray method using a spray gun or a high-speed gas flame spray method is applied. Usually, a spraying powder having a particle size of 15 to 53 μm is used for the plasma spraying method, and a spraying powder having a particle size of 5 to 45 μm or 15 to 53 μm is used for the high-speed gas flame spraying method. When these powders are coarser than the above-mentioned particle size range, it is difficult to form a dense thermal spray coating, and therefore, only a thermal spray coating having a low hardness can be obtained. In addition, when the particle size is finer than the above range, the fluidity of the powder is reduced, and the fine powder having high heat receiving efficiency is melted and deposited on the inner surface of the nozzle of the spray gun. Be impaired.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in comparison with a conventional example. The present invention is not limited to the following embodiments.

Example 1: WB containing 5.6% by weight of B
Powder, Co powder, Cr powder and Mo powder
0%, 18%, 8% and 4% by weight were collected and placed in a stainless steel container and placed in a vibrating ball mill for 2 hours.
The mixture was pulverized and mixed by a wet method for 4 hours. After the slurry taken out of the container is spray-dried in a non-oxidizing atmosphere and granulated, the powder obtained by sintering in vacuum is collected and sized into a powder of 5 to 45 μm by an air classifier. Thus, a powder for thermal spraying was prepared.

Table 1 shows the chemical composition of the obtained thermal spraying powder. Next, using this powder, high-speed gas flame spraying (fuel:
Hydrogen-oxygen), 0.4mm on SS400 substrate
A thick thermal spray coating layer was formed. Thereafter, the surface of the coating layer was removed by machining and surface polishing to obtain a test piece having a smoothness Δ.

As a result of identifying the thermal spray coating layer formed on the substrate surface by the Cu-κα X-ray diffraction method,
A ternary double boride phase of ₂ CoB ₂ was observed. Also EP
Table 2 shows the results of composition analysis of the coating layer by MA quantitative analysis. Vickers hardness (load:
0.3 kgf) is 1,230, using a reciprocating abrasion tester, according to the test method specified in JIS H8503, paragraph 9, using SiC polished paper No. 320 as the mating material, and setting the test load to 3. 0kgf, reciprocating load frequency 1,6
As a result of performing a wear resistance test on the test piece as 00 times, the weight loss on wear was 0.55 mg / cm ² .

On the other hand, the test piece was placed in an electric furnace at 600 ° C. for 30 minutes.
After holding for 1 minute, the heat cycle of quenching in water was repeated 20 times, and each time, the presence or absence of cracks or peeling occurring in the coating layer was visually observed and color checked to evaluate the thermal shock resistance. No abnormality was observed during the heat cycle, and it was found to have high thermal shock resistance. next,
When the test piece was kept in an electric furnace at 900 ° C. for 2 hours to measure the oxidation weight increase of the coating layer, the value was 3.5 mg /
cm ² , which was confirmed to have high oxidation resistance. Table 3 summarizes the results of the various characteristic tests described above. From the above results, the cermet sprayed coating according to the present invention, hardness,
It has excellent properties such as abrasion resistance, high-temperature oxidation resistance, thermal shock resistance and high-temperature hardness (heat resistance), and it can be said that the effectiveness of the present invention has been sufficiently proved.

Examples 2-4 and Conventional Examples 1-3: Example 1 except that the amount of powder to be mixed and the range of the classified particle size were changed.
Using the same raw material powder as above, a predetermined amount thereof was pulverized and mixed, granulated, and then sintered to obtain thermal spraying powders of Examples 2 to 4. Also,
W powder, Co powder and C powder and Cr powder, Ni
Using a predetermined amount of powder and C powder, WC-Co cermet thermal sprayed coating formed powder by the respective conventional method (conventional example 1-2) and _Cr 3 _C 2 -NiCr cermet sprayed coating forming powder (Conventional Example 3 )created. Table 1 also shows the chemical compositions of these powder compositions.

Next, using these thermal spray powders, in the same manner as in Example 1, test pieces having a thermal spray coating layer formed on a SS substrate by a high-speed gas flame spraying method were obtained. In the same manner, the composition analysis and the property test of the thermal spray coating layer were performed, and the results are shown in Tables 2 and 3, respectively.

[0025]

[Table 1] Chemical Chemistry Composition Grain Size Number WBCoCrMoCNi Range ─────────────────────────── ─────── Example 1 65.7 3.7 17.7 7.6 3.8 − − 5 to 45 Example 2 51.6 2.9 29.8 9.4 5.0 − − 15 to 53 Example 3 56.2 3.1 25.7 8.3 4.6 − − 15 to 53 Example 4 61.4 3.4 21.8 5.5 5.9 − − 5 to 45 Conventional example 1 bal − 12.0 − − 5.3 − 5 to 45 Conventional example 2 bal − 18.9 − − 5.0 − 15 to 53 Conventional example 3 − − − 68.2 − 10.4 20.8 5 to 45 ── ────────────────────────────────

[0026]

[Table 2] Implementation Chemistry Composition Number WBCoCrMoCNi Example 1 65.8 2.0 17.1 7.6 3.9--Example 2 51.4 1.5 29.7 9.5 5.0--Example 3 56.3 1.6 25.7 8.2 4.5--Example 4 61.4 1.9 21.8 5.5 6.0--Conventional example 1 81.9-9.2--4.9-Conventional Example 2 77.7-14.8--4.5-Conventional example 3---62.5-9.8 18.4 ───────────────────────────────

[0027]

[Table 3] Application Compound hardness Hv Abrasion resistance Thermal shock resistance High-temperature oxidation High-temperature hardness Number Physical phase (0.3 kg) mg / cm ² Number of repetitions mg / cm ² Hv (900 ° C) ────────────────────────────────── Example 1 W2CoB2 1230 0.55> 20 3.5 620 Example 2 W2CoB2 1115 0.66> 20 2.6 575 Example 3 W2CoB2 1165 0.65> 20 3.0 605 Example 4 W2CoB2 1190 0.59> 20 3.4 610 Conventional example 1 WC 1150 0.75 6 90 290 Conventional example 2 WC 1100 0.89 10 72 245 Conventional example 3 Cr3C2 850 1.28 11 3.1 380 ───────────────────────────────────

According to the above results, the boride-based cermet sprayed coating obtained by using the thermal spray powder according to the present invention has hardness and abrasion resistance comparable to the conventionally used WC-Co cermet sprayed coating. Cr ₃ C ₂ −
It can be seen that they have oxidation resistance and heat resistance that surpass those of the NiCr-based cermet sprayed coating, and have significantly higher thermal shock resistance than these conventional cermet sprayed coatings. Zn-0.15% Al molten at 470 ° C
A immersion test for 120 hours (5 days) was performed, and as a result, the weight loss of corrosion of Example 1 was 97 mg / cm ² , and the film residual ratio was 85.1%. Similarly, the weight loss of corrosion of Conventional Example 1 was 282 mg / cm ² , and the residual ratio of the coating was 33.9%. According to the results of the immersion test in the molten zinc and the molten aluminum, the cermet sprayed coating of the present invention showed It was confirmed that the corrosion resistance to the molten metal was much better than the conventional cermet sprayed coating.

[0029]

As described above, the sprayed boride-based cermet coating obtained by using the thermal spray powder of the present invention is excellent in hardness, wear resistance, corrosion resistance, heat resistance, and thermal shock resistance. Since it also has toughness, it can be used for a wide range of applications and can be said to be an industrially extremely useful invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 4/00-4/18 C04B 35/58 105 C22C 29/14 B22F 9 / 02,9 / 04

Claims (4)

(57) [Claims] 1. B2.5-4.0% by weight ratio, Co1
5.0 to 30.0%, Cr 5.0 to 10.0%, Mo
A boride-based cermet thermal spraying powder containing 3.0 to 6.0%, a composite powder composition comprising the balance W and unavoidable impurities. 2. The boride-based cermet thermal spray powder according to claim 1, wherein the particle size is 5 to 45 μm. 3. The boride-based cermet thermal spray powder according to claim 1, wherein the particle size is 15 to 53 μm. 4. The total amount of W and B is 52.5 to 70.0.
%, The total amount of Co, Cr and W is 25.0 to 45.0%
The boride-based cermet thermal spray powder according to any one of claims 1 to 3, wherein