Ni ALLOY WITH HIGH CORROSION RESISTANCE

Abstract

To provide a Ni alloy exhibiting superior corrosion resistance under high-temperature environments.SOLUTION: A Ni alloy contains Si, C, B, Co, Mo, Mn, Cr, and Fe; the total content of C and B is 2.3 mass% or less; the total content of Co, C, and B is 10.2 mass% or less; and the total content of B and Si exceeds 0.1 mass% and is less than 2.5 mass%. This Ni alloy has a metal structure that is a polycrystalline structure including a plurality of crystal grains and grain boundaries that contain Cr23C6 precipitates. Each crystal grain contains a NiCr matrix with Si, C, B, Co, Mo, Mn, or Fe dissolved therein, and Cr23C6 precipitates that are dispersed in this matrix.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This specification discloses a Ni alloy suitable for applications requiring corrosion resistance.

Background Art

[0002] As methods for forming a film on the surface of a metal product, a spraying method, a build-up welding method, a centrifugal casting method, etc. are known. A Ni-based self-fluxing alloy is suitable for this film. Japanese Patent Application Laid-Open No. 2015-143372 discloses a Ni-based self-fluxing alloy containing Si and B.

[0003] In general Ni-based self-fluxing alloys, a large amount of B and Si are added. B and Si are easily oxidized. When the film is subjected to heat treatment at about 1000 - 1100°C, a part of B becomes B2O3 and a part of Si becomes SiO2. By this heat treatment, metal oxides in the film and metal oxides on the film surface are dissolved, and borosilicate glass is formed and floats on the surface of the film like slag. In the film formed by this heat treatment, oxides and pores are extremely few. This film is dense.

[0004] The hardness of this film is about 15 - 60 HRC (200 - 700 HV). This film contains 1.0 - 4.5 mass% of B and 1.5 - 5.0 mass% of Si. In this film, coarse carbides and borides having a size of several tens of μm or more are crystallized. These carbides and borides contribute to the hardness and wear resistance of the film.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Due to carbon neutral policies, there are often cases where different usage environments from the past are required. Due to such diverse applications and usage environment changes, the required properties also vary widely, specializing in corrosion resistance, or wear resistance, or crack resistance / high toughness, etc. The required necessary properties and usage environments are diverse, and conventional materials can no longer cope. For example, conventional materials always contain B and Si, and since these elements were essential, hard borides and silicides always crystallized and could play an effective role in hardness and wear resistance. On the other hand, in places where crack resistance and high toughness are required rather than hardness and wear resistance, SFNi1 (15 - 30HRC), SFNi2 (30 - 40HRC), SFNi3 (40 - 50HRC), etc. have been used to suppress the crystallization of these hard phases by reducing the Cr content.

[0007] However, when used at even higher temperatures, the effects of B and Si, which were previously beneficial, may work adversely. When a Ni-based self-fluxing alloy containing a large amount of Si and B is placed in a high-temperature environment, a phenomenon occurs where low-melting-point components flow preferentially, and later high-melting-point components remain. This phenomenon is called "liquation segregation". In the alloy where liquation segregation occurs, since the low-melting-point components (quasi-ternary eutectic part) melt and flow away, the morphology of the structure cannot be maintained. Therefore, conventional Ni-based self-fluxing alloys are not suitable for applications in high-temperature environments (for example, 1100 °C or higher).

[0008] Furthermore, Ni-based self-fluxing alloys containing a large amount of B cause this B to form precipitates such as borides and Cr-Mo-B-based complex borides. These contribute to hardness. Also, their sizes contribute to wear resistance. Since conventional materials contain a large amount of B, they become coarse, more than several tens of μm. Therefore, even though they are excellent in hardness and wear resistance, local corrosion caused by potential differences occurs easily at the boundary between these precipitates and the matrix. Due to the coarse precipitates, the compositional gradient at the boundary between the precipitates and the matrix is distinct, and corrosion progresses as the potential difference between the precipitates and the matrix is maintained over a long period. Therefore, the corrosion resistance of conventional Ni-based self-fluxing alloys in high-temperature environments is insufficient.

[0009] The intention of the applicant is to provide a Ni alloy with excellent corrosion resistance in a high-temperature environment.

Means for Solving the Problems

[0010] The high-corrosion-resistance Ni alloy disclosed in this specification is Si: 0.5 mass% or more and 2.0 mass% or less, C: 0.2 mass% or more and 1.5 mass% or less, B: 0.1 mass% or more and 0.9 mass% or less, Co: 0.1 mass% or more and 8.0 mass% or less, Mo: 0.1 mass% or more and 2.0 mass% or less, Mn: 0.1 mass% or more and 1.0 mass% or less, Cr: 50.0 mass% or more and 60.0 mass% or less, and Fe: 0.1 mass% or more and 1.0 mass% or less and contains the balance of Ni and inevitable impurities. The total content of C and B is 2.3 mass% or less. The total content of Co, C and B is 10.2 mass% or less. The total content of B and Si exceeds 0.1 mass% and is less than 2.5 mass%. The microstructure of this Ni alloy is a polycrystalline structure having a plurality of crystal grains and grain boundaries containing Cr 23 C6 precipitates. Inside each crystal grain, there is a NiCr matrix in which Si, C, B, Co, Mo, Mn or Fe is dissolved, and Cr 23 C6 precipitates dispersed in this matrix.

[0011] Preferably, the size of the Cr 23 C6 precipitates is 5 μm or less. Preferably, the microstructure does not contain borides and complex borides.

[0012] Preferably, the solidus temperature of this Ni alloy is 1200 °C or higher.

[0013] The material of the high-corrosion-resistance powder disclosed in this specification is a Ni alloy. This Ni alloy is Si: 0.5 mass% or more and 2.0 mass% or less, C: 0.2 mass% or more and 1.5 mass% or less, B: 0.1 mass% or more and 0.9 mass% or less, Co: 0.1 mass% or more and 8.0 mass% or less, Mo: 0.1 mass% or more and 2.0 mass% or less, Mn: 0.1 mass% or more and 1.0 mass% or less, Cr: 50.0 mass% or more and 60.0 mass% or less, and Fe: 0.1 mass% or more and 1.0 mass% or less and contains the balance of Ni and inevitable impurities. In this Ni alloy, the total content of C and B is 2.3 mass% or less, the total content of Co, C and B is 10.2 mass% or less, and the total content of B and Si exceeds 0.1 mass% and is less than 2.5 mass%. The metal structure of this Ni alloy is a polycrystalline structure having a plurality of crystal grains and grain boundaries containing Cr 23 C6 precipitates. Inside each crystal grain, there is a NiCr matrix in which Si, C, B, Co, Mo, Mn or Fe is dissolved, and Cr 23 C6 precipitates dispersed in this matrix.

Advantages of the Invention

[0014] This Ni alloy is excellent in corrosion resistance in a high-temperature environment. From this Ni alloy, a dense layer can be formed due to the flux effect.

Brief Description of the Drawings

[0015]

Figure 1

Modes for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments will be described with appropriate reference to the drawings.

[0017] [Powder] The powder according to this embodiment is an aggregate of a large number of particles.

[0018] [Material] The material of this powder is a Ni alloy. This Ni alloy contains Si: 0.5 mass% or more and 2.0 mass% or less, C: 0.2 mass% or more and 1.5 mass% or less, B: 0.1 mass% or more and 0.9 mass% or less, Co: 0.1 mass% or more and 8.0 mass% or less, Mo: 0.1 mass% or more and 2.0 mass% or less, Mn: 0.1 mass% or more and 1.0 mass% or less, Cr: 50.0 mass% or more and 60.0 mass% or less, and Fe: 0.1 mass% or more and 1.0 mass% or less. Preferably, the balance is Ni and inevitable impurities.

[0019] In this Ni alloy, the total content ratio of C and B is 2.3 mass% or less. The total content ratio of Co, C, and B is 10.2 mass% or less. The total content ratio of B and Si exceeds 0.1 mass% and is less than 2.5 mass%.

[0020] [Metallographic structure] When coarse carbides and complex borides are present, the compositional gradient at the boundary between this compound and the matrix is large. If the potential difference state caused by this gradient persists for a long time, local corrosion will occur. In the metallographic structure according to this embodiment, complex borides can be eliminated. This metallographic structure has a simple structure in which fine Cr 23 C6 carbides are present at the grain boundaries and in the matrix. As shown in FIG. 1, these Cr 23 C6 precipitates are dispersed in the matrix. Si, C, B, Co, Mo, Mn, or Fe is dissolved in this matrix.

[0021] For example, if the cooling rate is of the order of furnace cooling and air cooling of the melt material, elements such as Si, C, B, Co, Mo, Mn, Fe, etc. are expelled outside the matrix and other precipitation phases are formed. Therefore, it is impossible to excessively contain these elements in the matrix as in the present invention. Such melt materials are extremely inferior in corrosion resistance. In this embodiment, as will be described in detail later, a quenched structure by atomization can be obtained. Therefore, these elements can be excessively dissolved in the matrix. In this metal structure, the corrosion resistance due to the dissolved elements and the corrosion resistance due to a small shade difference can be compatible. Furthermore, due to the fineness of the precipitation phase, even if local corrosion occurs, it is difficult for this to persist.

[0022] [Hardness] The powder according to this embodiment has a hardness of about 630 HV (100 gf). This hardness, when converted, is 56.8 HRC, indicating the same hardness as SFNi4, which is a Ni-based self-fluxing alloy. As described above, the metal structure of this powder is a simple structure in which fine Cr 23 C6 carbides are dispersed in the grain boundaries and the matrix. Therefore, the variation in hardness inside the powder is small. In conventional Ni-based self-fluxing alloys, high hardness has been achieved by the precipitation of Cr-Mo-B-based complex borides. In this embodiment, due to the uniform dispersion of fine Cr 23 C6 crystallites, a hardness equivalent to SFNi4 is achieved, and local corrosion at the boundary between the precipitation phase and the matrix is suppressed. This Ni alloy is a novel alloy not found in the prior art.

[0023] In this Ni alloy, 23 since there are few precipitates other than Cr

[0024] C6 crystallites, local corrosion due to the potential difference between this precipitate and the matrix is also unlikely to occur. This Ni alloy is excellent in corrosion resistance in a high-temperature environment. 23 From the viewpoint of corrosion resistance, the average size of the Cr

[0025] [Solidus temperature] In an alloy with an excessive total amount of Si and B, the solidus temperature is low, and thus the difference between the liquidus temperature and the solidus temperature is large. In this alloy, segregation occurs and its microstructure cannot be maintained. In an alloy with an excessive low total amount of Si and B, the effect that wollastonite glass is generated and floats on the surface of the film to make the film dense cannot be obtained. In the Ni alloy according to the present embodiment, as will be described in detail later, the content ratios of Si and B are appropriate. Therefore, the solidus temperature of this Ni alloy is sufficiently high. Even when this Ni alloy is placed in a high-temperature (for example, 1100 °C) environment, segregation hardly occurs. This Ni alloy is suitable for applications under high-temperature environments. This solidus temperature is preferably 1200 °C or higher, more preferably 1215 °C or higher, and particularly preferably 1225 °C or higher. From the viewpoint of the flux effect, the solidus temperature is preferably 1320 °C or lower, more preferably 1300 °C or lower, and particularly preferably 1280 °C or lower.

[0026] [Composition] Hereinafter, the elements contained in the Ni alloy will be described in detail.

[0027] [Silicon (Si)] Si can contribute to the flux effect. Si can further suppress the oxides of the Ni alloy. From these viewpoints, the content ratio of Si is more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, and particularly preferably 0.9% by mass or more. Excessive Si causes melting of the pseudo-ternary eutectic part. Excessive Si further inhibits the toughness and workability of the alloy. From the viewpoints of high-temperature properties, toughness, and workability, the content ratio of Si is preferably 2.0% by mass or less, more preferably 1.6% by mass or less, and particularly preferably 1.4% by mass or less.

[0028] [Carbon (C)] C in the Ni alloy, Cr 23It exists as C6. C is further dissolved in the matrix. C can contribute to the high-temperature properties and strength of the Ni alloy. From these viewpoints, the C content is more preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and particularly preferably 0.5% by mass or more. Excessive C inhibits the toughness and workability of the alloy. From the viewpoints of toughness and workability, the C content is preferably 1.5% by mass or less, more preferably 1.3% by mass or less, and particularly preferably 1.2% by mass or less.

[0029] [Boron (B)] B can contribute to the flux effect. B can further suppress the oxides of the Ni alloy. From these viewpoints, the B content is more preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and particularly preferably 0.4% by mass or more. Excessive B causes melting of the pseudo-ternary eutectic part. Excessive B can be a factor in local corrosion caused by complex borides. Excessive B further inhibits the toughness and workability of the alloy. From the viewpoints of high-temperature properties, corrosion resistance, toughness and workability, the B content is preferably 0.9% by mass or less, more preferably 0.8% by mass or less, and particularly preferably 0.7% by mass or less.

[0030] [Cobalt (Co)] Co is dissolved in the matrix. Co can contribute to the strength of the Ni alloy. From this viewpoint, the Co content is more preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and particularly preferably 2.0% by mass or more. Excessive Co inhibits the toughness and workability of the alloy. From the viewpoints of toughness and workability, the Co content is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, and particularly preferably 6.0% by mass or less.

[0031] [Molybdenum (Mo)] Mo exists in solid solution in the matrix. Mo can contribute to the corrosion resistance against local corrosion such as pitting corrosion and crevice corrosion. In particular, Mo can contribute to the corrosion resistance in an environment of non-oxidizing acids such as hydrochloric acid, sulfuric acid, acetic acid, and phosphoric acid. From this viewpoint, the content of Mo is more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more. Excessive Mo causes local corrosion due to the precipitation of Cr-Mo-B-based complex borides. Excessive Mo further inhibits the toughness and workability of the alloy. From the viewpoints of high-temperature properties, corrosion resistance, toughness, and workability, the content of Mo is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and particularly preferably 1.6% by mass or less.

[0032] [Manganese (Mn)] Mn exists in solid solution in the matrix. Mn can contribute to the strength of the Ni alloy. From this viewpoint, the content of Mn is more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and particularly preferably 0.4% by mass or more. Excessive Mn inhibits the toughness and workability of the alloy. From the viewpoints of toughness and workability, the content of Mn is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and particularly preferably 0.7% by mass or less.

[0033] [Chromium (Cr)] Cr exists in solid solution in the matrix. Cr can contribute to the corrosion resistance of the Ni alloy. Cr further exists as Cr 23 C6. Cr 23 C6 contributes to the high hardness of the Ni alloy. From these viewpoints, the content of Cr is more preferably 50.0% by mass or more, still more preferably 52.0% by mass or more, and particularly preferably 53.0% by mass or more. A Ni alloy containing excessive Cr may contain excessive Cr 23 C6. Excessive Cr 23C6 impairs the toughness of the Ni alloy. Furthermore, in a Ni alloy containing excessive Cr, the difference between the solidus temperature and the liquidus temperature is large. Therefore, when this Ni alloy is placed in a high-temperature environment, melting of the pseudo-ternary eutectic part is likely to occur. From the viewpoints of toughness and high-temperature characteristics, the Cr content is preferably 60.0 mass% or less, more preferably 59.0 mass% or less, and particularly preferably 58.0 mass% or less.

[0034] [Iron (Fe)] Fe exists in solid solution in the matrix. Fe can contribute to the strength of the Ni alloy. From this viewpoint, the Fe content is more preferably 0.1 mass% or more, still more preferably 0.2 mass% or more, and particularly preferably 0.3 mass% or more. Excessive Fe inhibits the toughness and workability of the alloy. From the viewpoints of toughness and workability, the Fe content is preferably 1.0 mass% or less, more preferably 0.8 mass% or less, and particularly preferably 0.7 mass% or less.

[0035] [Nickel (Ni)] The base material of this alloy is Ni. Ni can contribute to the low melting point of the alloy. Ni can further contribute to the corrosion resistance and toughness of the alloy. From these viewpoints, the Ni content is preferably 25 mass% or more, more preferably 30 mass% or more, and particularly preferably 35 mass% or more.

[0036] [C and B] The total content of C and B in the Ni alloy is 2.3 mass% or less. B, like C, can dissolve in the matrix. In an alloy in which the total content of C and B is 2.3 mass% or less, the C and B dissolved in the matrix are not excessive. This Ni alloy is excellent in toughness. From the viewpoint of toughness, this total content is more preferably 2.2 mass% or less, and particularly preferably 2.1 mass% or less. From the viewpoint of solid solution strengthening, this total amount is preferably 0.3 mass% or more, more preferably 0.7 mass% or more, and particularly preferably 1.0 mass% or more.

[0037] [Co, C and B] The total content of Co, C, and B in the Ni alloy is preferably 10.2 mass% or less. Co, like C and B, can dissolve in the matrix. In an alloy where the total content of Co, C, and B is 10.2 mass% or less, the Co, C, and B dissolved in the matrix are not excessive. This Ni alloy is excellent in toughness. From the perspective of toughness, this total content is more preferably 9.5 mass% or less, and particularly preferably 9.0 mass% or less. From the perspective of solid solution strengthening, this total amount is preferably 0.4 mass% or more, more preferably 1.0 mass% or more, and particularly preferably 1.5 mass% or more.

[0038] [Si and B] The total content of B and Si in the Ni alloy exceeds 0.1 mass% and is less than 2.5 mass%. Si and B can contribute to the flux effect. On the other hand, Si and B promote the melting of the pseudo-ternary eutectic part due to the low solidus temperature. In an alloy where the total content of B and Si is within the above range, the flux effect and high-temperature characteristics can be compatible. From this perspective, this total content is more preferably 0.5 mass% or more, and particularly preferably 0.7 mass% or more. This total content is more preferably 2.3 mass% or less, and particularly preferably 2.2 mass% or less.

[0039] [Production of powder] The powder is preferably obtained by the atomization method. The gas atomization method, disk atomization method, water atomization method, centrifugal atomization method, etc. are adopted. Preferred atomization methods are the gas atomization method and the disk atomization method. Mechanical milling or the like may be performed on the powder obtained by atomization.

[0040] In atomization, the molten Ni alloy is rapidly cooled and solidified. By this rapid cooling and solidification, a NiCr matrix solid-solved with Si, C, B, Co, Mo, Mn, or Fe is obtained. By the rapid cooling and solidification of the alloy having the above-described composition, Cr 23 A metal structure containing C6 and not containing coarse borides and complex borides can be obtained.

[0041] [Formation of film] From this Ni alloy, a film can be formed by various methods. Suitable methods for the film include the build-up welding method, the centrifugal casting method, the spraying method, and the thermal spraying method. In these methods, the powder is heated and then rapidly cooled to obtain the film. The material of this film is the same Ni alloy as the material of the powder. The metal structure of this Ni alloy has a polycrystalline structure including a plurality of crystal grains and grain boundaries containing Cr 23 C6 precipitates. Inside each crystal grain, there is a NiCr matrix in which Si, C, B, Co, Mo, Mn, or Fe is dissolved, and Cr 23 C6 precipitates dispersed in this matrix.

Example

[0042] Hereinafter, the effects of the Ni alloy according to the examples will be clarified, but the scope disclosed in this specification should not be construed in a limited manner based on the description of this example.

[0043] [Example 1] Raw materials having the composition shown in Table 1 were put into a refractory crucible. This raw material was inductively melted in argon gas to obtain a molten metal. This molten metal was discharged from the nozzle of the crucible, and high-pressure nitrogen gas was sprayed thereon to obtain powder. This powder was classified by a sieve, and the particle size was adjusted to 45 μm or more and 125 μm or less to obtain the powder of Example 1.

[0044] [Examples 2-20 and Comparative Examples 1-4] Powders of Examples 2-20 and Comparative Examples 1-4 were obtained in the same manner as in Example 1 except that the composition was as shown in Tables 1 and 2 below.

[0045]

Table 1

[0046]

Table 2

[0047] The alloys of each example and each comparative example contain inevitable impurities in addition to the elements shown in Table 1.

[0048] [Hardness] The powder was embedded in resin. This resin was polished, and the Vickers hardness of the exposed particles was measured. The test force was 0.98 N. The average value of the five measurement results is shown in Table 3 below.

[0049] [Solidus temperature and liquidus temperature] Using a thermal analyzer (DTA), the solidus temperature and liquidus temperature of the powder were measured under the following conditions. Amount of powder: 30 g Atmosphere: After evacuation, argon gas was flowed at 200 ml / min Heating rate: 20 °C / min Start temperature: Room temperature Reached temperature: 1500 °C (held for 5 minutes) Cooling rate: -20 °C / min Among the exothermic peaks seen in the DTA signal during cooling, the temperature at which exotherm starts at the highest temperature is the liquidus temperature, and the temperature at which exotherm ends at the lowest temperature is the solidus temperature. This result is shown in Table 3 below.

[0050] [Size of precipitate] The powder was embedded in resin. This resin was polished, and the cross-section of the exposed particles was photographed with a scanning electron microscope (SEM) to obtain a backscattered electron image at a magnification of 2000 times. Five precipitates were randomly selected from this electron image. The sizes of these precipitates were measured and classified according to the following criteria. A: The average size is 5 μm or less. B: The average size exceeds 5 μm. This result is shown in Table 3 below. No precipitate was observed in the powder according to Comparative Example 3.

[0051] [Sulfidation resistance] The powder was subjected to a salt spray test and a high-temperature and high-humidity test. The test conditions are as follows. Salt spray test Salt water concentration: 5% NaCl Temperature: 35 °C Time: 96 h High-temperature and high-humidity test Temperature: 70 °C Humidity: 95% RH Time: 96 h The powders after these tests were visually observed and classified according to the following criteria. A: There is rust on a part of the surface of the powder. B: Rust covers the entire surface of the powder. This result is shown in Table 3 below.

[0052]

Table 3

[0053] As shown in Table 3, the Ni alloys according to each example are excellent in various properties. From these evaluation results, the superiority of this Ni alloy is clear.

Industrial Applicability

[0054] The Ni alloy described above is suitable for machine parts and the like. This alloy is particularly suitable for the coatings of aircraft, automobiles, manufacturing equipment, etc.

Claims

1. Si: 0.5% by mass or more and 2.0% by mass or less, C: 0.2% by mass or more and 1.5% by mass or less, B: 0.1% by mass or more and 0.9% by mass or less, Co: 0.1% by mass or more and 8.0% by mass or less, Mo: 0.1% by mass or more and 2.0% by mass or less, Mn: 0.1% by mass or more and 1.0% by mass or less, Cr: 50.0% by mass or more and 60.0% by mass or less, and Fe: 0.1% by mass or more and 1.0% by mass or less and contains the balance being Ni and inevitable impurities, the total content of C and B being 2.3% by mass or less, the total content of Co, C and B being 10.2% by mass or less, a highly corrosion-resistant Ni alloy in which the total content of B and Si exceeds 0.1% by mass and is less than 2.5% by mass, the metal structure of the above Ni alloy being a polycrystalline structure having a plurality of crystal grains and grain boundaries containing Cr ２３ C ６ precipitates, inside each crystal grain, there is a NiCr matrix in which Si, C, B, Co, Mo, Mn or Fe is dissolved, and Cr ２３ C ６ precipitates dispersed in this matrix, a highly corrosion-resistant Ni alloy.

2. Cr ２３ C ６ The Ni alloy according to claim 1, wherein the size of the precipitates is 5 μm or less.

3. The Ni alloy according to claim 1 or 2, wherein the metal structure does not contain borides and complex borides.

4. The Ni alloy according to claim 1 or 2, wherein its solidus temperature is 1200 °C or higher.

5. A highly corrosion-resistant powder whose material is a Ni alloy, wherein the Ni alloy contains Si: 0.5% by mass or more and 2.0% by mass or less, C: 0.2% by mass or more and 1.5% by mass or less, B: 0.1% by mass or more and 0.9% by mass or less, Co: 0.1% by mass or more and 8.0% by mass or less, Mo: 0.1% by mass or more and 2.0% by mass or less, Mn: 0.1% by mass or more and 1.0% by mass or less, Cr: 50.0% by mass or more and 60.0% by mass or less, and Fe: 0.1% by mass or more and 1.0% by mass or less, with the balance being Ni and inevitable impurities, wherein the total content of C and B is 2.3% by mass or less, the total content of Co, C and B is 10.2% by mass or less, the total content of B and Si exceeds 0.1% by mass and is less than 2.5% by mass, wherein the metal structure of the Ni alloy is a polycrystalline structure having a plurality of crystal grains and grain boundaries containing Cr C ２３ C ６ precipitates, wherein the interior of each crystal grain contains a NiCr matrix in which Si, C, B, Co, Mo, Mn or Fe is dissolved, and Cr ２３ C ６ precipitates dispersed in this matrix, a highly corrosion-resistant powder.

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