KR20150105284A - Alloy compositions for improved adhesion and corrosion rate of the sprayed coating - Google Patents

Abstract

The present invention relates to an alloy composition for a thermal spray coating containing chromium, boron, silicon, nickel, niobium, molybdenum, manganese, an evaporation loss as main ingredients in order to improve attachment performance during spraying and improve corrosion resistance of an attached coating. According to the present invention, the alloy composition for a thermal spray coating composed of 13.2 wt% of Cr, 2.56 wt% of B, 3.71 wt% of Si, 5.59 wt% of Ni, 6.57 wt% of Nb, 0.33 wt% of Mo, 0.73 wt% of Mn, 0.07 wt% of Fe as evaporation conservation, and the balance of Fe.

Description

[0001] The present invention relates to an alloy composition for spray coating having improved adhesion rate and corrosion resistance,

The present invention relates to an alloy composition for thermal spray coating which contains chromium, boron, silicon, nickel, niobium, molybdenum, manganese, and evaporation loss as main components to improve the deposition rate during spraying and improve the corrosion resistance of the deposited coating.

In order to meet wear resistance requirements, a technique has been proposed in which a coating layer is formed using a modified alloy that is transformed into an amorphous material when it is subjected to conventional friction, thereby improving wear resistance using the friction transition curing and friction coefficient reduction effect of the coating layer . For example, in the form of a wire, U.S. Patent No. 4725512 discloses a Fe-Cr-B-based core wire. In the modified alloy, when the molten metal is sprayed during the process of spraying, part of the molten metal solidifies as amorphous during quenching while it is changed into amorphous structure by friction, so that it has a high temperature hardness, a low coefficient of friction and a high thermal shock resistance, Is widely used. However, such a Fe-Cr-B-based alloy has a disadvantage that it is easily worn out due to initial wear before friction.

In order to solve such shortcomings of wear and tear, for example, Korean Patent Registration No. 10-0499820 has proposed a cored wire having a boride-modified modified alloy system. However, in the case of the boron-modified modified alloy system, the abrasion resistance against the initial abrasion was improved, but the adhesion was poor and the corrosion occurred in the aqueous solution.

In addition, both of the Fe-Cr-B series of US Patent No. 4725512 and the amorphous alloy of Korean Patent Registration No. 10-0499820 both have a high deposition rate of about 40-50% and are highly wasteful and deteriorate in a high temperature environment or an aqueous solution There were disadvantages.

10-0690281, 10-0974806 10-0974807, etc. in the form of powders and 10-0690287 in case of 10-0690281, the hardness is only Hv 600-700 when the coating is formed by spraying, but the corrosion resistance is insufficient, There were disadvantages. In the case of crystalline, the corrosion is easily progressed in the corrosive environment because the potential difference between the grain and the segregation part and the grain boundary in the mouth are different from each other. However, in the case of amorphous, there is no grain boundary and segregation and the whole becomes homogeneous unstable state, So that corrosion resistance is very excellent. However, there is no process of transition to 100% amorphous, some remain as crystalline, and the residual crystal part becomes a cause of corrosion. 10-0690281 suggests that the residual crystalline portion is vulnerable to corrosion when it is excessively dependent on amorphous.

 10-0974806 and 10-0974807 showed high hardness of Hv900-1000 and low coefficient of friction in protective lubrication was excellent for wear resistance and low friction but it was corroded like 10-0974806 in water. Therefore, the residual crystalline portion also needs to have corrosion resistance. In the case of these powder forms, the deposition rate is about 38%, which is a disadvantage in cost increase. A mixture of amorphous and crystalline may be more advantageous in terms of abrasion resistance, but may also cause problems in corrosion resistance.

The present invention has been made to solve the above-mentioned problems of the prior art and to add various other advantages, and in particular, it is an object of the present invention to provide a film forming apparatus, Molybdenum and manganese as main components to improve the adhesion rate in the molten state and improve the corrosion resistance in a high temperature oxidizing atmosphere or in an aqueous solution to thereby provide an alloy composition for a thermal spray coating which is improved in corrosion resistance and in corrosion resistance, The purpose is to provide.

The above object is achieved by the alloy composition for thermal spray coating according to the present invention, which comprises 13.2% by weight of chromium (Cr), 2.56% by weight of boron (B), 3.71% by weight of silicon (Si), 5.59% by weight of nickel (Ni) (Fe) as evaporation preservative (Va), 0.07% by weight of iron (Fe), and the remaining balance of iron (Fe).

A boiler water pipe may be provided wherein the adhesion rate is improved to about 80% and the Vickers hardness of the coating is 1,000 to 1,300 Hv when the cored wire according to the embodiments of the present invention is manufactured and spray coated.

When the core wire or powder according to the present invention having the above-described constitution is formed and the coating is formed using the spraying process, the adhesion rate is increased and the corrosion resistance to the high temperature oxidizing atmosphere and the aqueous solution is improved, There is a remarkable effect such as protecting the base material in the environment.

FIG. 1 is a graph showing X-ray diffraction analysis results of an amorphous core wire (Wire 3) according to an embodiment of the present invention and a conventional coating wire made of a cored wire (Wire 2, Wire 1) (a) and the cohesion diagram (b).
Fig. 2 is a surface comparison photograph showing corrosion resistance test results of a cored wire having improved corrosion resistance according to an embodiment of the present invention and a conventional cored wire (Wire 2, Wire 1).
FIG. 3 is a graph illustrating the corrosion behavior of the conventional cored wire (Wire 3) and conventional cored wire (Wire 2, Wire 1) according to an embodiment of the present invention, Showing graph.
FIG. 4 is a graph showing the corrosion behavior of high-temperature corrosion (high-temperature oxidation) test of cored wire according to an embodiment of the present invention and conventional cored wire (Wire 2, Wire 1) Graph showing comparison.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. And are intended to fully inform the person skilled in the art the scope of the invention and are defined by the claims of the invention.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, a core wire having improved adhesion and corrosion resistance according to a specific embodiment of the present invention will be described.

 The conventional wire disclosed in U.S. Patent No. 4725512 includes iron (Fe), chromium (Cr), boron (B), silicon (Si), and manganese (Mn) (B), silicon (Si), molybdenum (Mo) and manganese (Mn) in comparison with the conventional wire disclosed in JP-A-0499820, An alloy composition for the production of an amorphous film having improved corrosion resistance, a cored wire or a powder made of the same is characterized by containing at least one of Fe, Cr, B, Si, Ni, (Mo) and manganese (Mn). The core wire according to the present invention further includes nickel (Ni) and niobium (Nb) compared to conventional core wires, and the component content thereof can be determined so as to improve toughness, adhesion, and corrosion resistance.

The core wire of the embodiment of the present invention comprises 46.5 to 79.9 wt% of iron (Fe), 10 to 25 wt% of chromium (Cr), 1.0 to 5.0 wt% of boron (B) 3.0 to 7.0% by weight of nickel, 4.0 to 8.0% by weight of niobium, 0.1 to 1.5% by weight of molybdenum and 0.5 to 2.0% by weight of manganese (Mn). On the other hand, when the coating is formed by the spraying process, the evaporation preservation amount (Va) may be further included in the range of 0 to 5 parts by weight based on the total weight. Elements constituting the alloy composition of the present invention, the cored wire made of such an alloy composition, the powder made of such an alloy composition and the like are as follows.

1) Iron (Fe): As a component of the matrix according to the present invention, it may contain about 46.5 to 79.5% by weight, depending on the contents of other components.

2) Chromium (Cr): Generally, amorphous alloys are produced at a very fast cooling rate, but chromium improves the amorphous formability of Cr-Fe-B compounds and has oxidation resistance such as Cr ₂ O ₃ and FeOCr ₂ O ₃ Chromium compounds are formed so as to inhibit the generation of oxides of Fe along with high strength, thereby securing the oxidation resistance of the modified alloy. According to the present invention, such chromium is preferably added at a content ratio of 10 to 25% by weight, more preferably 10 to 17% by weight. When chromium is added in an amount of less than 10% by weight, the effect of adding chromium can not be sufficiently exhibited. When chromium exceeds 25% by weight, the effect of high chromium steel promotes the formation of? -Fe phase, Can not do it.

3) Boron (B): Boron is added to the core powder of the cored wire according to the present invention to increase the wear resistance and determine the crystalline-amorphous transformation. The boron is preferably contained in an amount of 1.0 to 5.0% by weight. If the content of boron is less than 1.0 wt%, the above-mentioned effect can not be obtained. If the boron content exceeds 5.0 wt%, a large amount of boride is produced, which results in weak corrosion resistance and increased brittleness.

4) Silicon (Si): Silicon improves oxidation resistance and promotes amorphous phase formation. The silicon is preferably added in an amount of 1.5 to 5.0% by weight. If when silicon is added in less than 1.5% by weight, it is difficult to expect the above-described oxidation resistance improved and the amorphous phase formation promoting effect, more than 5.0% by weight, but not the oxidation resistance life longer increases, rather Fe ₂ Si, Fe ₃ Si or the like is formed, which is an undesirable problem.

5) Nickel (Ni): Nickel interferes with the formation of α-Fe by iron, thus helping to form amorphous phase. Nickel is preferably added in an amount of 3.0 to 7.0% by weight based on the total weight of the alloy composition. Such nickel has an advantage of improving the wettability and greatly improving the adhesion. When nickel is added in an amount of less than 3.0 wt%, the above effect is difficult to be expected. When the nickel content is more than 7.0 wt%, iron is formed in a γ-Fe phase.

6) Niobium (Nb): Niobium plays a role in ensuring formation of amorphous phase and ensuring oxidation resistance. Such niobium has an advantage of improving the wettability and greatly improving the adhesion. Niobium is easily combined with oxygen in an iron-based amorphous alloy to form oxides such as NbO ₂ and Nb ₂ O _{5. The} niobium oxide is superior in oxidation resistance to chromium oxide. It is preferable that 4.0 to 8.0 wt% of niobium is added. When niobium is added in an amount of less than 4.0 wt%, the above effects are hardly expected. When it is more than 8.0 wt%, amorphous phase formation is difficult to expect.

7) Molybdenum (Mo): Molybdenum constitutes hard particles and improves abrasion resistance. The molybdenum is preferably added in an amount of 0.1 to 1.5% by weight. If molybdenum (Mo) is added in an amount of less than 0.1% by weight, the effect of improving the wear resistance due to the addition of molybdenum (Mo) is insufficient. Conversely, if the Mo content exceeds 1.5% by weight, the releasability is improved but the wettability is deteriorated, .

8) Manganese (Mn): Mn (Mn) serves to stabilize the amorphous phase. The manganese (Mn) is preferably added in an amount of 0.5 to 2.0 wt%. If manganese (Mn) is added in an amount of less than 0.5% by weight, the effect of adding manganese (Mn) can not be obtained, and if it exceeds 2.0% by weight, oxidation resistance is deteriorated.

9) Evaporation component (Va): In the alloy composition, cored wire, or powder, a component that evaporates and prevents oxidation during coagulation in the melt, and a part of the essential composition is evaporated or reacted according to the melting time length, It is not possible to form a film of a desired composition because it is not remained. Therefore, it is preferable to add the vaporization preservation amount in the range of 0 to 5 parts by weight based on the total weight of the above-described alloy composition. Such evaporation preservatives include chromium (Cr), boron (B), niobium (Nb), molybdenum (Mo), titanium (Ti), phosphorus (P), carbon (C) and the like. At this time, titanium, phosphorus, and carbon are used to minimize evaporation because they trap the elements that are mixed with the evaporation preservative. At this time, the evaporation preservation amount is not used when passing through a process without evaporation loss such as sintering which does not melt the powder.

 When the cored wire of the present invention is used to apply arc spraying, it is possible to obtain a hard coating having an adhesion efficiency of about 80% and a Vickers hardness of 1,000 to 1,300 Hv in the adhesive coat layer.

Hereinafter, a specific embodiment of the present invention will be described.

1. Preparation of sample

In order to explain the characteristics of the present invention, as shown in the following Table 1, a core wire having a conventional amorphous characteristic, that is, a conventional wire (Wire 1) disclosed in U.S. Patent No. 4725512, No. 10-0499820, the cored wire (Wire 3) according to one embodiment of the present invention, and the physical and chemical properties of a boiler water tube coated with the surface thereof using these wires . The numbers in Table 1 below represent the content ratio (wt%) of each component.

Name of sample Fe Cr Si B C Ni Nb Mo Mn Remarks Wire 1 68 26.21 1.38 3.37 0.083 - - - 1.15 Conventional Wire 2 71.4 22.77 1.28 1.87 1.02 - - 0.71 0.83 Conventional Wire 3 67.24 13.2 3.71 2.56 0.07 5.59 6.57 0.33 0.73 Invention

2. Phase analysis

The surface of the boiler water tube was coated with the samples 1, 2, and 3 having the chemical composition shown in Table 1 above to form a protective coating layer for the boiler water pipe made of an amorphous alloy layer. In this amorphous alloy layer, X Ray diffraction analysis. The results are shown in the graph of FIG.

As can be seen from FIG. 1, in the case of the conventional wire 1, a larger amount of the? -Fe phase than the other products, that is, the wire 2 and the wire 3, is observed. This is because the chromium content is much contained . When the chromium component is contained in a large amount, the above-mentioned result is obtained and the formation of the amorphous phase is prevented. In addition, in the case of Wire 1, more boride phase was detected than in other products because the content of boron (B) is larger than that of other products. If the boron (B) content is higher than the reference value, a boride is formed to improve the hardness, but the brittleness is increased, and it is difficult to ensure oxidation resistance

On the other hand, in the case of the conventional wire 2, it can be seen that a large amount of carbide is formed as compared with other products. This is because the carbon content is 1.0 wt% or more. When the carbon content is 1.0 wt% or more, formation of amorphous phase can be ensured, but oxidation resistance is deteriorated when carbide is formed.

However, in the case of Wire 3 of the present invention, by controlling the carbon content to 1.0 wt% or less, toughness, adhesion rate and corrosion resistance are improved as compared with other products, and a large amount of amorphous phase is formed. Thus, mechanical properties are improved, and boride and carbide formation It can be understood that the oxidation resistance is excellent.

3. Hardness characteristics

Name of sample Primary measurement Secondary measurement Third measurement Fourth measurement 5th measurement Average Wire 1 1002 959 1088 966 1032 1009.4 Wire 2 1072 1114 1186 1168 1277 1163.4 Wire 3 1182 1355 1183 1253 1113 1217.2

In Table 2, the surface of the boiler water tube was coated with the samples Wire 1, Wire 2, and Wire 3 shown in Table 1 above to form a protective coating layer of a boiler water pipe made of an amorphous alloy layer. In this amorphous alloy layer The results of measuring the Vickers hardness are shown. The numbers in Table 2 represent Vickers hardness (Hv).

As can be seen from Table 2, the wire 3 of the present invention shows much improved hardness characteristics because a larger amount of amorphous phase is formed than conventional wires.

4. Corrosion resistance (oxidation resistance)

FIG. 2 is a graph showing the results of coating a surface of a boiler water tube using Wire 1, Wire 2, and Wire 3 shown in Table 1 above to form a protective coating layer of a boiler water pipe made of an amorphous alloy layer, NaCl aqueous solution and the surface of the amorphous alloy layer was observed with time.

As can be seen in FIG. 2, after about 72 hours had elapsed, it was found that the wire 3 of the present invention did not produce iron oxide on the surface. This shows that Wire 3 of the present invention is superior in corrosion resistance to other products.

5. Corrosion behavior (co-electrification test)

Name of sample Corrosion potential (eV) Corrosion current (A / cm2) Wire 1 - 0.42 2.78 ㅧ 10 ^-6 Wire 2 - 0.55 4.65 ㅧ 10 ^-6 Wire 3 - 0.43 1.34 ㅧ 10 ^-6

FIG. 3 is a graph showing the results of coating the surface of a boiler water tube using Wire 1, Wire 2, and Wire 3 of Table 1 above to form a protective coating layer of a boiler water pipe made of an amorphous alloy layer, NaCl solution, and then observed the corrosion behavior through the co-electromotive force test in aqueous solution. The corrosion potential (eV) and the corrosion current (A / cm 2) measured in the above-mentioned coercive electrification test are as shown in Table 3 above.

As can be seen from Table 3 and FIG. 3, the corrosion rate of Wire 3 of the present invention was the lowest at 1.34 ㅧ 10 ^-6 as a result of the co-electrification test. In the case of conventional wire 2, the corrosion rate was the highest at 4.65 ㅧ 10 ^-6 . As a result, it was found that the wire 3 of the present invention was about 3.7 times better in corrosion resistance than the conventional wire 2.

6. High Temperature Corrosion (High Temperature Oxidation) Characteristics

FIG. 4 is a graph showing the results of coating a surface of a boiler water tube using the samples Wire 1, Wire 2, and Wire 3 shown in Table 1 above to form a protective coating layer of a boiler water pipe made of an amorphous alloy layer, And then the weight was measured with time.

As can be seen from FIG. 4, the wire 3 of the present invention showed about twice the oxidation resistance at a high temperature of 1,000 ° C., compared with the conventional Wire 1 and Wire 2.

Claims (4)

13.2 wt% of Cr, 2.56 wt% of boron, 3.71 wt% of silicon, 5.59 wt% of nickel, 6.57 wt% of niobium, 0.33 wt% of molybdenum, Mn of 0.73 wt%, iron (Fe) of 0.07 wt% as an evaporation preservative (Va), and iron (Fe) of the remaining balance as an evaporation preservative (Va). A cored wire for thermal spray coating, which is made of the alloy composition for thermal spraying according to claim 1. A powder for thermal spray coating, which is made of the alloy composition for thermal spraying according to claim 1. A boiler water tube characterized by being sprayed with the alloy composition for thermal spraying according to claim 1.

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