HIGH MELTING POINT Ni-BASED ALLOY CONTAINING P

Abstract

To be able to form a coating having low solidus line temperature, and easily excellent in corrosion resistance, cracking resistance and high toughness at low temperature.SOLUTION: By mass%: P: 0.1 to 7.0%, B: 5.0% or less, Si: 5.0% or less, C: 2.0% or less, Cr: 30.0% or less, one or both of Mo and W with (Mo+W) / 2 of 9.0% or less, Cu: 10.0% or less, one or at least two of Mn, Fe, or Co each 10.0% or less, the remainder being Ni and unavoidable impurities, constitute a Ni-based alloy. The alloy has a structure in which a hard phase containing 1% or less of P and compounds of 10 μm or smaller in which P is either dissolved in or contained in the γ-Ni matrix are dispersed, and further has a solidus temperature of 800°C to 950°C, resulting in a highly meltable Ni-based alloy.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a Ni-based self-fluxing alloy containing P, its atomized powder, and a metal coating and steel part using the alloy, which have excellent corrosion resistance, crack resistance, and toughness. In particular, the present invention relates to a high-melting Ni-based alloy that has a low solidus temperature, allows for low-temperature coating formation and densification treatment, and has a structure in which P is solid-solved and / or P-containing compounds are finely dispersed in a γNi matrix. [Background technology]

[0002] Conventionally, self-fluxing alloys include Ni-based alloys and Co-based alloys specified in Japanese Industrial Standard (JIS) H8303 (self-fluxing alloy thermal spraying). These self-fluxing alloys are mainly used in surface treatments such as thermal spraying and overlay welding, and are used to form coatings with excellent corrosion resistance and wear resistance. The hardness of these coatings is approximately 15 to 60 HRC.

[0003] In thermal spraying using nickel-based and cobalt-based alloys containing flux components such as boron (B) and silicon (Si), a dense coating can be obtained by performing a fusing process after thermal spraying. The components specified in JIS H8303 require that B be contained in the range of approximately 1.0 to 4.5 mass% and Si be contained in the range of approximately 1.5 to 5.0 mass%.

[0004] The fusing temperature is usually around 1000-1200°C. During this process, some of the easily oxidized B and Si in the alloy become B2O3 and SiO2, dissolving the metal oxides in the thermal spray coating and on the substrate surface, forming a type of borosilicate glass that floats to the surface of the thermal spray coating like slag. This flux action results in a thermal spray coating with very few oxides and pores. During this fusing process, the spray particles fuse together within the thermal spray coating, resulting in a uniform structure. Furthermore, interdiffusion occurs between the substrate and the thermal spray coating during fusing, forming an alloy layer several tens of microns thick at the boundary, which is metallurgically bonded.

[0005] Thus, self-fluxing alloys, which contain primary and eutectic oxides and carbides in their structure, exhibit excellent wear resistance and corrosion resistance in various corrosive environments such as hydrochloric acid, sulfuric acid, hydrofluoric acid, and caustic soda.

[0006] Self-fluxing alloys are primarily used in surface treatments such as thermal spraying and overlay welding, forming coatings with excellent corrosion and wear resistance. Their hardness is approximately 15 to 60 HRC. Regarding the density of the coating, the characteristics of self-fluxing alloys are described below. Specified in JIS H 8303 (self-fluxing alloy thermal spraying), these alloys contain flux components such as B and Si in nickel-based and cobalt-based alloys. A dense coating can be obtained by performing a fusing process after thermal spraying. The JIS-specified components essentially contain approximately 1.0 to 4.5 mass% B and 1.5 to 5.0 mass% Si.

[0007] Typically, this fusing is performed at a temperature of around 1000-1200°C. During this process, some of the easily oxidized B and Si in the alloy become B2O3 and SiO2, dissolving the metal oxides in the thermal spray coating and on the substrate surface, forming a type of borosilicate glass that floats to the surface of the thermal spray coating like slag. This flux action tends to produce a thermal spray coating with few oxides and pores. Furthermore, during this fusing, the spray particles fuse together within the thermal spray coating, facilitating a homogenous structure. Furthermore, interdiffusion occurs between the substrate and the thermal spray coating during fusing, forming an alloy layer of several tens of microns at the boundary, facilitating metallurgical bonding.

[0008] Self-fluxing alloys contain primary and eutectic oxides and carbides in their structure, and are therefore generally expected to have excellent wear resistance, as well as corrosion resistance in various corrosive environments such as hydrochloric acid, sulfuric acid, hydrofluoric acid, and caustic soda.

[0009] The applicant of the present application has also discovered that the composition of the present invention is P: 0.2-6.0%, B: 0.1-4.5%, Si: 0.1-5.0%, C: 0.00-2.00%, Cr: 0.0-30.0%, Mo: 0.0-9.0%, W: 0.0-18.0%, Cu: 0.0-10.0%, Mn: 0.0-10.0%, Fe: 0.0-10.0%, Co: 0.0-10.0%, Al: 0.00-0.20%, Ti: 0.00-0.20%, Zr: 0.00-0.20%, Hf: 0.00-0.20%, and that the composition satisfies 2.3≦P%+B%+Si%≦ We have proposed a Ni-based self-fluxing alloy that satisfies the following conditions: 11.0, Mo%+W% / 2≦9.0, Al%+Ti%+Zr%+Hf%≦0.20 (see Patent Application 1). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2023-31420

[0011] [Non-Patent Document 1] JIS H8303:2010 "Self-fluxing alloy thermal spraying" Summary of the Invention [Problem to be solved by the invention]

[0012] In recent years, the applications of self-fluxing alloys for surface treatment have expanded, and applications to a wide range of fields, such as aircraft, automobiles, boilers, and agricultural machinery, which require greater durability than previous applications, are being considered. Therefore, the required properties are increasing so that the alloys can be used in different environments in addition to the traditional applications.

[0013] Until now, it has been common to use high-melting-point substrates, typically Fe-based, such as SUS304 (melting point 1398-1427°C) and general structural steel (melting point approximately 1580°C), and then coat them with a Ni-based self-fluxing alloy to improve corrosion resistance, wear resistance, etc. Therefore, the temperature during application such as thermal spraying and the subsequent remelting process has had little effect on the melting and deformation of the substrate.

[0014] On the other hand, for components that require high thermal and electrical conductivity, surface treatments are also required for substrates with lower melting points than conventional materials, such as Cu (melting point 1084°C). However, when forming a coating using a Ni-based self-fluxing alloy on such low-melting-point substrates, the temperature during application as well as the temperature during the remelting process have a significant impact on the substrate. Remelting with conventional Ni-based self-fluxing alloys requires remelting at around 1000-1200°C, which inevitably leads to melting and deformation of the substrate, as well as deterioration of the substrate's properties due to these thermal effects.

[0015] In addition, the higher the temperature during coating application or remelting treatment, the more easily the contained B diffuses, reacting with Fe, Cr, etc. in the substrate and crystallizing hard, coarse borides, which may impair the adhesion between the substrate and the coating.

[0016] Furthermore, the crystal grains of the stainless steel substrate become coarse, causing a decrease in strength, and the corrosion resistance at the interface with the Ni-based self-fluxing alloy coating may be excessively deteriorated.

[0017] In addition, the higher the temperature during coating application and remelting, the more fuel is used, resulting in large amounts of CO2 emissions.

[0018] In addition, in conventional materials, B and Si crystallize hard borides and silicides, which play an effective role in improving hardness and wear resistance. However, in situations where crack resistance and high toughness are more important than hardness and wear resistance, attempts have been made to address this by lowering the Cr content to suppress the crystallization of these hard phases, such as SFNi1 (15-30 HRC), SFNi2 (30-40 HRC), and SFNi3 (40-50 HRC). However, because these conventional materials only control the hardness of the hard phase crystallization, it is impossible to achieve both hardness and toughness. Furthermore, the reduction in hard phases makes it difficult to obtain other properties such as wear resistance.

[0019] To address these issues, there is a need for the development of high-melting Ni-based alloys that can be processed and densified at lower temperatures than conventional materials and that can be used in a wider range of fields and applications.

[0020] The Ni-based self-fluxing alloy of Patent Document 1 contains P, so its solidus or liquidus temperature is low, allowing a coating to be formed by treatment at a relatively low temperature, and the main part is less likely to be exposed to high temperatures. However, because the remelting heat treatment temperature remains high as in the past, coarse P compounds tend to form, a fine structure is not obtained, and the substrate is prone to deformation when forming the coating, which is still not satisfactory.

[0021] Therefore, the present invention aims to provide (1) a high-melting Ni-based alloy and atomized powder that, by containing P, has a lower solidus temperature than conventional self-fluxing alloys (JIS H 8303), allowing for easy film formation at low temperatures and enabling subsequent heat treatment to form a dense film at low temperatures, and (2) has a structure in which P is solid-solved and / or compounds containing P are finely dispersed in a γNi matrix. It is also an object of the present invention to provide a film using this that has excellent corrosion resistance, crack resistance, and high toughness, and to provide a part equipped with such a film. [Means for solving the problem]

[0022] Therefore, the inventors thought that if they could have a eutectic structure at a temperature lower than the conventional Ni-Si-B ternary eutectic temperature, they might be able to lower the solidus temperature, and focused on P. The eutectic temperature of Ni-P is 870°C, and it was thought that adding P would result in a solidus temperature that was dramatically lower than that of conventional materials (Ni-Si-B system).

[0023] In fact, it was found that by substituting B and Si for P, the alloy takes on a Ni-Ni3P eutectic structure rather than a CrP compound, and this has succeeded in lowering the solidus temperature by more than 100°C compared to conventional alloys.

[0024] This makes it possible to process at lower temperatures than before, which solves all of the problems, such as melting and deformation of the substrate during the remelting process, reduced adhesion between the substrate and the coating due to hard and coarse borides created by the diffusion of B, reduced strength and corrosion resistance due to coarsening of the substrate's crystal grains, and increased CO2 emissions due to increased fuel use.

[0025] Furthermore, because low-temperature processing is now possible, when applying a coating, for example when spraying atomized powder of the material of the present invention to form a coating, spraying can be done at a lower temperature than before, and we have succeeded in not only the remelting process but also in lowering the temperature during spraying. Also, whereas there was a limit to the spraying distance in the past, it is now possible to spray over longer distances, which has led to improved handling during spraying.

[0026] By adding P, P dissolves in the γNi matrix and / or disperses compounds containing P with a size of 10 μm or less, forming a mesh-like network structure, improving the strength of the matrix. Furthermore, because compounds with a size of 10 μm or less are finely dispersed in the Ni-Ni3P eutectic, it is possible to maintain uniform strength in the matrix, and a uniform hardness is obtained as a coating. This has succeeded in achieving not only wear resistance, but also both hardness and toughness, which was previously difficult to achieve.

[0027] As such, there has been no detailed study of the effects of P and its organizational structure to date.

[0028] Therefore, the first means for solving the problems of the present invention is to P: 0.1-7.0%, B: 0.0 (including 0%) to 5.0%, Si: 0.0 (including 0%) to 5.0% C: 0.0 (including 0%) to 2.0%, Cr: 0.0 (including 0%) to 30.0%, Mo,W: One or both of Mo and W are mixed in Mo+W / 2, with 0.0% (including 0%) to 9.0%. Cu: 0.0 (including 0%) to 10.0% Mn, Fe, Co: One or more of Mn, Fe, and Co are each 0.0% (including 0%) to 10.0%. A Ni-based alloy consisting of the remainder Ni and unavoidable impurities, It has a structure in which P is dissolved in a hard phase having a P content of 1% or less and a γNi matrix in which P is dispersed and / or compounds containing P are dispersed in a size of 10 μm or less. Furthermore, it has a solidus temperature of 800°C or higher and 950°C or lower. It is a high melting Ni-based alloy characterized by the following. Here, the term "high melting property" means that the alloy is self-fluxing, i.e., it is an alloy that melts easily at low temperatures and is easy to process.

[0029] The second means is that the hard phase is a boride or a carbide, The equivalent circle diameter is 20 μm or less, The high melting property Ni-based alloy according to the first aspect is characterized in that the area ratio is 20% or less.

[0030] The third aspect of the present invention is a high melting point Ni-based alloy according to the first or second aspect, characterized in that it has a liquidus temperature of 1000°C or higher.

[0031] The fourth aspect is a high melting property Ni-based alloy coating made of the high melting property Ni-based alloy according to any one of the first to third aspects.

[0032] The fifth means is the high melting property Ni-based alloy coating according to the fourth means, characterized in that the coating is in a state where it has been remelted at less than 940°C, the porosity of the coating is such that the porosity in the remelted coating / the porosity in the thermal sprayed coating ≦0.5, and further the coating has a γNi matrix containing P with a network structure.

[0033] The sixth aspect of the present invention is an atomized powder for forming a coating, which is made of the high melting Ni-based alloy according to any one of the first to third aspects.

[0034] The seventh aspect of the present invention is a part having the coating according to the fourth or fifth aspect, and having excellent hardness, corrosion resistance, and crack resistance. [Effects of the Invention]

[0035] The addition of P allows processing at lower temperatures than conventional methods, thereby resolving a variety of issues, including melting and deformation of the substrate during remelting, reduced adhesion between the substrate and the coating due to the formation of hard, coarse borides caused by the diffusion of B, reduced strength and corrosion resistance due to coarsening of the substrate's crystal grains, and increased CO2 emissions due to increased fuel consumption. Furthermore, the ability to perform low-temperature processing means that when applying a coating, for example, by thermal spraying the atomized powder of the material of the present invention, it can be sprayed at lower temperatures than conventional methods, providing the benefits of low temperatures not only for the remelting process but also for thermal spraying. Furthermore, whereas conventional methods limited the spraying distance, it is now possible to spray over longer distances, leading to improved handling during thermal spraying.

[0036] Furthermore, by adding P, P dissolves in the γNi matrix and / or disperses P-containing compounds of 10 μm or less, forming a mesh-like network structure, which improves the strength of the matrix. Furthermore, because the Ni-Ni3P eutectic contains finely dispersed compounds of 10 μm or less, the matrix maintains uniform strength, and the coating also achieves uniform hardness. This not only improves wear resistance, but also achieves both hardness and toughness, which was previously difficult to achieve. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is an optical microscope image showing a cross-sectional microscopic image of an as-sprayed coating formed by thermal spraying a Ni-based alloy having the composition of the present invention onto a substrate. [Figure 2] FIG. 2 is an optical microscope image of an example of the present invention showing a cross-sectional micrograph of the coating shown in FIG. 1 after remelting treatment at less than 940°C. [Figure 3]FIG. 3 is an optical microscope image of a comparative example showing a cross-sectional micrograph of the coating shown in FIG. 1 after remelting treatment at 940° C. or higher. DETAILED DESCRIPTION OF THE INVENTION

[0038] Before describing the embodiments of the present invention, the reasons for specifying the components of the alloy of the present invention will be explained. Note that % in the following components means % by mass.

[0039] P: 0.1 to 7.0% In the alloy of the present invention, P is an essential element for lowering the solidus temperature. However, if added in excessive amounts, coarse phosphides crystallize, resulting in excessively high hardness, embrittlement of the coating, and difficulty in machining. If added less than 0.1%, the effect of lowering the solidus temperature is insufficient, and if added in excess of 7.0%, the liquidus temperature rises excessively. The P content is preferably more than 0.2% and less than 6.0%, and more preferably more than 0.5% and less than 5.0%.

[0040] In particular, the effect of P makes it possible to achieve an unprecedentedly low solidus temperature that could not be achieved by adding B or Si alone, making remelting treatment possible at temperatures below 1000°C, or even below 950°C, and even at the lowest temperatures in the 800°C range.

[0041] Because the solidus temperature is so low, thermal spraying can be performed at a lower temperature than before. This means that not only can the coating be applied by remelting, but it can also be applied by reducing the thermal energy used during coating by 10 to 20 percent.

[0042] Furthermore, if the coating is produced under conventional application conditions, it is possible to extend the distance during coating application (spraying distance) to 1.5 times the normal distance.

[0043] Here, it is presumed that the significant effect of adding P in lowering the solidus temperature is due to the fact that the solidus temperature in the binary phase diagram with Ni is significantly lower at approximately 870°C for P compared to approximately 1093°C for B and approximately 1143°C for Si.

[0044] Furthermore, the addition of P suppresses the deterioration of corrosion resistance at the interface between the substrate and the coating. When this alloy was sprayed onto a SUS304 substrate, remelted, and subjected to a salt spray test, rusting at the interface was suppressed compared to a conventional P-free Ni self-fluxing alloy. Microstructural observation of the interface with the substrate revealed that in the conventional P-free Ni self-fluxing alloy, the B contained in the Ni self-fluxing alloy diffused excessively to the grain boundaries of the SUS304 substrate, reacting with Cr in the SUS304 to form Cr-based borides. As a result, the Cr concentration in the surrounding SUS304 matrix decreased, a phenomenon similar to the so-called sensitization of stainless steel was observed, and corrosion resistance was deteriorated. In contrast, in the P-containing alloy of the present invention, this grain boundary diffusion of B was suppressed, and it is presumed that the P, which diffuses to grain boundaries in the same way as B, suppressed the diffusion of B. In addition, the grain boundary diffusion of B in a P-free Ni self-fluxing alloy generates Cr and Mo borides in a SUS316 base material, for example, which deteriorates the corrosion resistance of the surrounding base material, and in a mild steel base material, the generated Fe borides themselves have lower corrosion resistance than the surrounding base material.

[0045] Furthermore, P promotes densification even in as-sprayed coatings that have not undergone remelting treatment. While the detailed reasons for this phenomenon are unclear, it is presumed that, in addition to simply having a low solidus temperature, oxides containing P with relatively low sublimation temperatures gasify slightly while the alloy particles fly at high temperatures during thermal spraying, reducing the amount of oxide in the coating. In other words, in the thermal spraying method, slight oxidation of the particles is unavoidable while the particles fly at high temperatures, but it is presumed that the effect of these oxides, which inhibits densification of the coating, is neutralized or reduced by gasification.

[0046] In addition, P improves the strength of the matrix by dispersing P-containing and / or P-containing compounds of 10 μm or less in size in the γNi matrix, forming a network structure. The dark gray areas in Figures 2 and 3 correspond to the dispersed P-containing and / or P-containing compounds of 10 μm or less. Furthermore, the fine dispersion of compounds of 10 μm or less in the Ni-Ni3P eutectic maintains uniform matrix strength and provides uniform hardness for the coating. This not only improves wear resistance, but also achieves both hardness and toughness, which was previously difficult to achieve. A uniform hardness structure with finely dispersed P compounds can be achieved, for example, by adding P and remelting the coating at a temperature lower than 940°C.

[0047] B: 0.0 to 5.0% In the alloy of the present invention, B may be added as needed to lower the solidus temperature and reduce oxides in the coating. Part of B and Si converts to B2O3 and SiO2, dissolving metal oxides in the thermal spray coating and on the substrate surface. This forms a type of borosilicate glass, which floats to the surface of the thermal spray coating like slag, acting as a flux, reducing oxides and pores in the thermal spray coating and increasing its density. However, excessive addition raises the liquidus temperature due to the crystallization of coarse borides. Furthermore, the formation of borides increases the hardness. Since P lowers the solidus temperature, no addition is necessary. However, adding more than 5.0% of B excessively raises the liquidus temperature, so the content is preferably less than 4.0%, and more preferably less than 2.0%.

[0048] Si: 0.0 to 5.0% In the alloy of the present invention, Si may be added as needed to lower the solidus temperature and reduce oxides in the coating. Some of the B and Si form B2O3 and SiO2, dissolving metal oxides in the thermal spray coating and on the substrate surface. This forms a type of borosilicate glass, which acts as a flux and floats to the surface of the thermal spray coating like slag, effectively reducing oxides and pores in the thermal spray coating and increasing its density. However, adding too much Si can make the coating excessively hard, embrittling it and making it difficult to machine. Since P plays a role in lowering the solidus temperature, no addition is necessary. Adding more than 5.0% Si results in excessively high hardness, so the content is preferably less than 4.0%, more preferably less than 3.0%.

[0049] C: 0.0 to 2.0% In the alloy of the present invention, C has the effect of increasing hardness and may be added as needed. However, if too much C is added, the coating becomes excessively hard, making it brittle and difficult to machine. If more than 2.0% is added, the coating becomes excessively hard. Preferably, the content is less than 1.8%, more preferably less than 1.6%.

[0050] Cr: 0.0 to 30.0% In the alloy of the present invention, Cr has the effect of improving corrosion resistance and may be added as needed. However, if the content exceeds 30.0%, the liquidus temperature will rise excessively. Preferably, the content is less than 20.0%, more preferably less than 18.0%.

[0051] Mo+W / 2: 0.0-9.0% In the alloy of the present invention, Mo and W have the effect of improving corrosion resistance and may be added as needed. The effect of W is half that of Mo, in terms of mass percent. However, excessive addition raises the liquidus temperature and generates coarse phosphides containing high concentrations of Mo and / or W, resulting in excessively high hardness, embrittlement of the coating, and difficulty in machining. Addition of more than 9.0% Mo+W / 2 excessively raises the liquidus temperature. The amount is preferably less than 5.0%, more preferably less than 4.0%.

[0052] Cu: 0.0 to 10.0% In the alloy of the present invention, Cu has the effect of improving corrosion resistance and may be added as needed. However, excessive addition of Cu reduces corrosion resistance. If Cu is added in excess of 10.0%, corrosion resistance will decrease. The Cu content is preferably less than 5.0%, more preferably less than 4.0%.

[0053] Mn, Fe, Co: 0.0 to 10.0% In the alloy of the present invention, Mn, Fe, and Co are elements that do not have a significant effect on the properties, and may be added up to an upper limit of 10% each.

[0054] (Organizational characteristics) The structure is one in which P is dissolved in a hard phase with a P content of 1% or less and a γNi matrix in which P is dispersed and / or compounds containing P with a size of 10 μm or less are dispersed. P is present only in trace amounts in the hard phase, primarily in the γNi matrix. The dispersion of P in solid solution and / or P-containing compounds of 10 μm or less (the dark gray areas in Figures 2 and 3) and their mesh-like network structure improve the strength of the matrix. Furthermore, the fine dispersion of compounds of 10 μm or less in the Ni-Ni3P eutectic maintains uniform strength in the matrix, resulting in uniform hardness for the coating. This not only improves wear resistance, but also makes it possible to achieve both hardness and toughness, which was previously difficult.

[0055] Solidus temperature is between 800℃ and 950℃ The addition of P lowers the solidus temperature, but on the other hand, the liquidus temperature changes depending on the content of Cr, B, Si, etc. If the solidus temperature exceeds 950°C, the thermal impact on the substrate during remelting processing becomes significant.

[0056] Liquidus temperature of 1000°C or higher The alloy of the present invention preferably has a liquidus temperature of 1000° C. or higher. If the liquidus temperature is less than 1000° C. and the temperature range between the solidus and liquidus is very narrow, the remelting treatment conditions become difficult.

[0057] The hard phase is a boride or carbide, the equivalent circle diameter of which is 20 μm or less, and the area ratio of which is 20% or less. If 20% or more of the coarse hard phases exceeding 20 μm (the size is calculated as the equivalent circle diameter), the material will be excessively hard, causing embrittlement and making machining difficult. Furthermore, since corrosion also occurs at the grain boundaries of the hard phases, if the size of the hard phases is less than 20 μm and their area ratio exceeds 20%, corrosion is likely to progress. On the other hand, if the size of the hard phases exceeds 20 μm and their area ratio is 20% or less, cracks may originate from the coarse hard phases, affecting machinability. Therefore, it is preferable that the equivalent circle diameter size is 20 μm or less and the area ratio is 20% or less.

[0058] The porosity of the coating that has been remelted at less than 940°C is ≦0.5, i.e., the porosity in the remelted coating / the porosity in the thermal spray coating. Even if the solidus temperature is lowered, if the remelting treatment is performed at 940°C or higher, for example, at the conventional temperature of around 1000°C, the coating will naturally become dense (porosity: porosity in the remelted coating / porosity in the thermal spray coating ≦0.5). For example, Patent Document 1 only performs the remelting treatment at 940°C, and in that case, the coating will naturally become dense (porosity: porosity in the remelted coating / porosity in the thermal spray coating ≦0.5). However, because the temperature is too high, the material melts and is unable to maintain its shape, resulting in sagging. On the other hand, in the present invention, both the above-mentioned structure and densification can be achieved by performing treatment at an even lower temperature, below 940°C.

[0059] Comparing Figure 1, which shows the sample before remelting at low temperature, with Figure 2, which shows the sample after remelting at low temperature, it can be seen that the voids have been reduced in Figure 2. Furthermore, if the remelting temperature is too high, a coarse structure will be formed, as shown in Figure 3.

[0060] (Example) How to make the powder The raw materials weighed out to the compositions shown in Nos. 1 to 20 in Table 1 were melted in a vacuum melting furnace and atomized with high-pressure nitrogen gas to obtain gas atomized powders. These powders were classified by sieving to obtain powders with a particle size range of 45 μm to 125 μm, and used as test powders.

[0061] [Table 1]

[0062] On the evaluation of the solidus temperature of powders. The solidus temperature of the test powder was evaluated using a thermal analyzer (DTA). Approximately 30 g of powder was used for the measurement. After evacuation, Ar gas was flowed at 200 ml / min. The powder was heated from room temperature to 1500°C at a rate of 20°C / min and held at 1500°C for 5 minutes. After holding at 1500°C, the powder was cooled to room temperature at a rate of -20°C / min. The solidus temperature was determined by the lowest temperature at which the exothermic peaks that appeared in the DTA signal during cooling ceased.

[0063] About the production method of thermal spray coating A 50 x 50 x 9 mm SUS304 plate was used as a substrate. After blasting the 50 x 50 mm surface, the test powder was atmospherically plasma sprayed to obtain a coating. The substrate was cooled with air during the spraying process. The substrate with the sprayed coating was then placed in an electric furnace and heated to a temperature above the solidus temperature but below 940°C in an Ar flow, as shown in Table 2 for invention examples 1 to 12. The temperature was then held for 20 minutes, and the furnace was cooled to obtain a fused coating. The coating thickness was approximately 300 μm. The remelting treatment temperatures for the comparative examples were as shown in Table 2, and comparisons were also made at temperatures above 940°C.

[0064] Evaluation of residual pores and residual oxides in thermal spray coatings Test specimens for cross-sectional observation were cut out from the thermal spray coating before remelting treatment and the coating that had been remelted (in the present invention, the remelting treatment was performed at a temperature above the solidus temperature and below 940°C), polished, and photographs were taken of the center of the coating in the thickness direction at 100x magnification using an optical microscope, and the total number of residual pores of 20 μm or more and residual oxides in a 500 μm square was evaluated. If the shape of the photographed residual pores or residual oxides was elliptical rather than circular, the number of pores with a major axis of 20 μm or more was calculated. Evaluation was performed using the value of number of remelted coatings / number of thermal spray coatings.

[0065] Corrosion resistance evaluation of thermal sprayed and remelted coatings A corrosion resistance test was conducted on a cross-section of the remelted coating (in the present invention, the remelting was performed at a temperature above the solidus temperature but below 940°C), which was then polished. A salt spray test (5% NaCl, 35°C, 96 hours) was conducted, and samples in which rusting was limited to a small area on the coating and / or at the interface between the coating and the base metal were rated as A, while samples in which rusting was widespread were rated as B.

[0066] Hardness evaluation of remelted coating The remelting treatment was carried out at a temperature above the solidus temperature and below 940°C. The cross section of the remelting treatment film was cut out and polished to evaluate the Vickers hardness. The test force was 2.94 N, and the average value of five measurements was used to evaluate the hardness.

[0067] Evaluation of deformation of substrate after remelting treatment When the remelted coating (including the substrate) was placed on a flat base, those that were not in contact with the base were judged to be deformed. (In the present invention, the remelting was performed at a temperature above the solidus temperature but below 940°C.) Those that were in contact with the base were rated A, and those where the substrate placed on the base was not in contact with the base and was unstable and wobbly were rated B.

[0068] [Table 2]

[0069] In the Ni-based alloys of invention examples 1 to 12, the remelting heat treatment temperatures for all of the coatings were low, at 850 to 920°C, the size of the P compounds in the coatings was 10 μm or less, the circle-equivalent diameter of the hard phase containing almost no P was 20 μm or less, and the porosity of the coatings was 0.5 or less in all cases, resulting in a structure with finely dispersed P. Thus, coatings with a rating of A were obtained, which exhibited excellent corrosion resistance and substrate deformation evaluation. Furthermore, the P content of the hard phase in the invention examples was approximately 0.04 to 0.09%, and the P content in the hard phase was 1% or less, as determined by SEM / EDS analysis. Therefore, uniform strength of the matrix, uniform hardness of the coating, and a balance between hardness and toughness were achieved.

[0070] In Comparative Example No. 13, P was not added to the Ni-based alloy, and the solidus temperature was high, so the remelting heat treatment temperature was also high, and deformation of the substrate was observed. In Comparative Example No. 14, P was excessive, coarse P compounds were crystallized, and deformation of the substrate was also observed due to the high remelting heat treatment temperature. Comparative Example No. 15 contained excessive amounts of P and Cu, and was therefore inferior in corrosion resistance. In addition, deformation of the substrate was also observed. In Comparative Example No. 16, the film was too hard due to the excess B, Si, and C, coarse P compounds were observed, the corrosion resistance was poor, and deformation of the substrate was also observed. In Comparative Example No. 17, the Cr content was excessive, the liquidus temperature was elevated, coarse P compounds were observed, the corrosion resistance was poor, and deformation of the substrate was also observed. In Comparative Example No. 18, the Ni-based alloy did not contain P, and the solidus temperature was high, so the remelting heat treatment temperature was also high, resulting in deformation of the substrate. In addition, the total amount of Mo and W and the total amount of Mn, Fe, and Co were all excessive, so the liquidus temperature was excessively high, the coating was too hard, and the corrosion resistance was poor. In Comparative Examples 19 and 20, the remelting heat treatment temperature was as high as 940° C., so coarse P compounds were observed and deformation of the substrate was also observed. [Industrial Applicability]

[0071] The present invention can lower the remelting heat treatment temperature of thermal sprayed coatings, and therefore can be widely applied to fields such as aircraft, automobiles, boilers, and agricultural machinery, in addition to situations where thermal sprayed coatings of Ni-based self-fluxing alloys have traditionally been used.

Claims

1. By mass% P: 0.1-7.0%, B: 0.0 (including 0%) to 5.0%, Si: 0.0 (including 0%) to 5.0% C: 0.0 (including 0%) to 2.0%, Cr: 0.0 (including 0%) to 30.0%, Mo, W: One or both of Mo and W are 0.0 (including 0%) to 9.0% at Mo+W / 2; Cu: 0.0 (including 0%) to 10.0%, Mn, Fe, Co: one or more of Mn, Fe, and Co are each 0.0 (including 0%) to 10.0%; The balance is a Ni-based alloy consisting of Ni and unavoidable impurities, The alloy has a structure in which P is dissolved in a hard phase having a P content of 1% or less and a γNi matrix in which P is dispersed and / or a compound containing P and having a size of 10 μm or less is dispersed, Further, it has a solidus temperature of 800°C or higher and 950°C or lower. A highly meltable Ni-based alloy characterized by:

2. The hard phase is borides and carbides, The equivalent circle diameter is 20 μm or less, 2. The high melting property Ni-based alloy according to claim 1, wherein the area ratio is 20% or less.

3. 3. The high melting point Ni-based alloy according to claim 1, which has a liquidus temperature of 1000°C or higher.

4. A high melting property Ni-based alloy coating comprising the high melting property Ni-based alloy according to claim 1 or 2.

5. A high melting property Ni-based alloy coating comprising the high melting property Ni-based alloy according to claim 3.

6. A coating in a state that has been remelted at less than 940°C, wherein the porosity of the coating is such that the porosity in the remelted coating / the porosity in the thermal spray coating is ≦0.5; Furthermore, the coating has a network structure of a γNi matrix containing P. The high melting property Ni-based alloy coating according to claim 5, characterized in that

7. A part having excellent hardness, corrosion resistance and crack resistance, which has the coating according to claim 5.

8. A part having excellent hardness, corrosion resistance, and crack resistance, which has the coating according to claim 6.

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