Fe-based alloy build-up layer and method for forming same

Abstract

The present invention addresses the problem of providing a build-up layer that can have improved corrosion resistance and wear resistance, and provides an Fe-based alloy build-up layer which contains C, Si, Mn, Cr, Mo, and V, with the remainder comprising Fe and unavoidable impurities, wherein: the contents of C, Si, Mn, Cr, Mo, and V respectively satisfy 1.60 mass% ≤ C ≤ 3.50 mass%, 0.20 mass% ≤ Si ≤ 1.50 mass%, 0.20 mass% ≤ Mn ≤ 1.50 mass%, 14.0 mass% ≤ Cr ≤ 26.0 mass%, 0.2 mass% ≤ Mo ≤ 2.0 mass%, and 4.0 mass% ≤ V ≤ 8.0 mass%; in a cross-section of the Fe-based alloy build-up layer, the ratio of the total area of fine granular carbides having a diameter of 5 µm or less to the area of the observation region is 0.50% to 4.00% inclusive; and the amount of Cr solid solution contained in the primary crystal of the Fe-based alloy build-up layer is 5 mass% or more.

Description

Fe-based alloy cladding layer and method for forming same

[0001] The present invention relates to a build-up layer formed of an Fe-based alloy having a predetermined composition and a method for forming the same.

[0002] The invention described in Patent Document 1 aims to provide an Fe-based alloy that, when used in melt solidification forming such as build-up welding or additive manufacturing, can produce build-up layers, additive manufacturing products, and the like that have high wear resistance and toughness.

[0003] To achieve this objective, the Fe-based alloy described in Patent Document 1 contains 0.5≦C≦0.9 mass%, 0.5≦Si≦3.0 mass%, 0.1≦Mn≦1.0 mass%, 3.0≦Cr≦8.0 mass%, and 0.1≦Mo≦4.0 mass%, with the balance consisting of Fe and unavoidable impurities, and satisfies −0.5>Si−(5C+2Mn)>−3.0. In the Fe-based alloy described in Patent Document 1, the Cr content is set within the above-mentioned numerical range, thereby improving hardenability and corrosion resistance.

[0004] The invention described in Patent Document 2 aims to form a build-up layer that exhibits the properties of martensitic stainless steel, including wear resistance, even when normal quenching is omitted in post-weld heat treatment, by using an Fe-based alloy powder that can serve as a build-up material for forming a build-up layer of martensitic stainless steel containing Cr.

[0005] To achieve this object, the Fe-based alloy powder described in Patent Document 2 contains C: 1.4 mass% to 3.5 mass%, V: 2.0 mass% to 10.0 mass%, Cr: 15.0 mass% to 20.0 mass%, Mo: less than 8.0 mass%, Si: less than 2.0 mass%, Mn: less than 2.0 mass%, the balance being Fe and unavoidable impurities, and {4.2C-V} satisfies 2.1 mass% to 6.1 mass%. In the Fe-based alloy powder described in Patent Document 2, the Cr content is set within the above-mentioned numerical range, thereby improving corrosion resistance.

[0006] JP 2022-144437 A JP 2020-032449 A

[0007] An object of the present invention is to provide a build-up layer having excellent corrosion resistance and wear resistance, and a method for forming the same.

[0008] The inventors focused on the composition of the Fe-based alloy, the area of ​​granulated carbides contained in the buildup layer formed from the Fe-based alloy, and the amount of soluble Cr in the primary crystals contained in the buildup layer, and discovered that by adjusting these, the corrosion resistance and wear resistance of the buildup layer can be improved, leading to the completion of the present invention.

[0009] That is, the present invention provides the following inventions. [1] An Fe-based alloy overlay layer containing C, Si, Mn, Cr, Mo and V, with the balance being Fe and unavoidable impurities, wherein C, Si, Mn, Cr, Mo and V have the following respective contents: 1.60 mass%≦C≦3.50 mass% 0.20 mass%≦Si≦1.50 mass% 0.20 mass%≦Mn≦1.50 mass% 14.0 mass%≦Cr≦26.0 mass% 0.2 mass%≦Mo≦2.0 mass% 4.0 mass%≦V≦8.0 mass% In a cross section of the Fe-based alloy overlay layer, the ratio of the total area of ​​fine-grained carbides having a diameter of 5 μm or less to the area of ​​the observation region is 0.50% or more and 4.00% or less, and the amount of Cr solid solution contained in the primary crystals of the Fe-based alloy overlay layer is 5 mass% or more. [2] The Fe-based alloy cladding layer according to [1], wherein the amount of soluble Cr is an average value of the amount of Cr detected at a plurality of points in the primary crystal. [3] A method for forming an Fe-based alloy cladding layer on a substrate, the method comprising: (a) melting an Fe-based alloy powder to obtain a molten metal, and (b) solidifying the molten metal on the substrate, wherein the Fe-based alloy powder contains C, Si, Mn, Cr, Mo, and V in the following amounts, with the balance being Fe and unavoidable impurities: 1.60 mass%≦C≦3.50 mass%, 0.20 mass%≦Si≦1.50 mass%, 0.20 mass%≦Mn≦1.50 mass%, 14.0 mass%≦Cr≦26.0 mass%, 0.2 mass%≦Mo≦2.0 mass%, and 4.0 mass%≦V≦8.0 mass%. The method of melting the Fe-based alloy powder under heat treatment conditions such that the ratio of the total area of ​​fine carbides having a diameter of 5 μm or less to the area of ​​an observation region in a cross section of the Fe-based alloy cladding layer is 0.50% to 4.00%, and the amount of Cr solid solution contained in the primary crystals of the Fe-based alloy cladding layer is 5 mass% or more. [4] The method of [3], in which the Fe-based alloy powder is melted using laser cladding with a laser output set to 500 to 9000 W. [5] The method of [3] or [4], in which the particle size of the Fe-based alloy powder is 150 μm or less.

[0010] According to the present invention, the corrosion resistance and wear resistance of the buildup layer can be improved.

[0011] The Fe-based alloy powder for forming the build-up layer (hereinafter referred to as "the Fe-based alloy powder of the present invention") will be described below.

[0012] (Composition of Fe-Based Alloy Powder) The Fe-based alloy powder of the present invention contains C, Si, Mn, Cr, Mo, and V, with the remainder being Fe and unavoidable impurities. The contents (mass%) of C, Si, Mn, Cr, Mo, and V satisfy the conditions shown in the following formulas (1) to (6): 1.60 mass%≦C≦3.50 mass% (1) 0.20 mass%≦Si≦1.50 mass% (2) 0.20 mass%≦Mn≦1.50 mass% (3) 14.0 mass%≦Cr≦26.0 mass% (4) 0.2 mass%≦Mo≦2.0 mass% (5) 4.0 mass%≦V≦8.0 mass% (6)

[0013] (C content: 1.60 mass% or more and 3.50 mass% or less) C is an element that forms carbides with Cr or V, thereby contributing to improving the wear resistance of the buildup layer. By setting the C content to 1.60 mass% or more, sufficient hardness can be obtained. The C content is preferably 1.70 mass% or more, more preferably 1.80 mass% or more. On the other hand, if the C content is higher than 3.50 mass%, the carbides become coarse and the toughness of the buildup layer is reduced, so the C content is set to 3.50 mass% or less. The C content is preferably 3.00 mass% or less, more preferably 2.40 mass% or less. With regard to the C content, each of the above lower limit values ​​may be combined with any of the above upper limit values.

[0014] (Si content: 0.20 mass% or more and 1.50 mass% or less) Si is an element that improves the hardness, high temperature resistance, and toughness of the buildup layer by dissolving in the matrix in Fe. By setting the Si content to 0.20 mass% or more, the hardness and high temperature resistance of the buildup layer can be improved. The Si content is preferably 0.25 mass% or more, more preferably 0.30 mass% or more. On the other hand, by setting the Si content to 1.50 mass% or less, the toughness of the buildup layer can be improved. The Si content is preferably 1.40 mass% or less, more preferably 1.30 mass% or less. With regard to the Si content, each of the above lower limit values ​​may be combined with any of the above upper limit values.

[0015] (Mn content: 0.20 mass% or more and 1.50 mass% or less) Mn is an element that can improve the strength of the buildup layer. The Mn content is 0.20 mass% or more. The Mn content is preferably 0.25 mass% or more, more preferably 0.30 mass% or more. On the other hand, if the Mn content is too high, the toughness of the buildup layer may be reduced. Furthermore, Mn bonds with S to form MnS, which may reduce the toughness of the buildup layer and promote cracking of the buildup layer during processing. In consideration of these points, the Mn content is set to 1.50 mass% or less. The Mn content is preferably 1.40 mass% or less, more preferably 1.00 mass% or less. With regard to the Mn content, each of the above lower limit values ​​may be combined with any of the above upper limit values.

[0016] (Cr content: 14.0 mass% or more and 26.0 mass% or less) Cr is an element that can improve the corrosion resistance of the buildup layer. The Cr content is 14.0 mass% or more. The Cr content is preferably 15.0 mass% or more, more preferably 16.0 mass% or more. On the other hand, if Cr is added in excess, a ferrite phase that inhibits the buildup layer from being hardened may be excessively formed in the buildup layer. Therefore, the Cr content is set to 26.0 mass% or less. The Cr content is preferably 25.0 mass% or less, more preferably 24.0 mass% or less. With regard to the Cr content, each of the above lower limit values ​​may be combined with any of the above upper limit values.

[0017] (Mo content: 0.2 mass% or more and 2.0 mass% or less) Mo is an element that contributes to improving the strength of the buildup layer by dissolving in the primary crystals of the buildup layer. The Mo content is 0.2 mass% or more. The Mo content is preferably 0.3 mass% or more, more preferably 0.5 mass% or more. On the other hand, if Mo is added in excess, excessive carbides (carbides larger than the fine granular carbides described below) may precipitate, and these excessive carbides will impair the toughness of the buildup layer. In order to ensure the toughness of the buildup layer, the Mo content is set to 2.0 mass% or less. The Mo content is preferably 1.9 mass% or less, more preferably 1.8 mass% or less. With regard to the Mo content, each of the above lower limits may be combined with any of the above upper limits.

[0018] (V content: 4.0 mass% or more and 8.0 mass% or less) V combines with C to form fine carbides (fine-grained carbides described below), and the formed carbides contribute to improving the wear resistance of the buildup layer. The V content is 4.0 mass% or more. The V content is preferably 4.5 mass% or more, more preferably 5.0 mass% or more. On the other hand, if excessive V is added, excessive carbides (carbides larger than the fine-grained carbides described below) may precipitate, and these excessive carbides will hinder the toughness of the buildup layer. In order to ensure the toughness of the buildup layer, the V content is 8.0 mass% or less. The V content is preferably 7.5 mass% or less, more preferably 7.0 mass% or less. With regard to the V content, each of the above lower limits may be combined with any of the above upper limits.

[0019] (Inevitable Impurities) Examples of unavoidable impurities include elements having the following contents (% by mass). The unavoidable impurities may be composed of one type of element or two or more types of elements. "REM" means rare earth elements. 0 mass%<Co≦0.05 mass% 0 mass%<Cu≦0.50 mass% 0 mass%<Sn≦0.05 mass% 0 mass%<Nb≦0.05 mass% 0 mass%<Ta≦0.05 mass% 0 mass%<Ti≦0.05 mass% 0 mass%<Zr≦0.05 mass% 0 mass%<B≦0.01 mass% 0 mass%<Ca≦0.01 mass% 0 mass%<Se≦0.03 mass% 0 mass%<Te≦0.01 mass% 0 mass%<Bi≦0.01 mass% 0 mass%<Pb≦0.05 mass% 0 mass%<Mg≦0.02 mass% 0 mass%<REM≦0.01 mass%

[0020] (Method for producing Fe-based alloy powder) The Fe-based alloy powder of the present invention can be produced by powdering a molten Fe-based alloy. The Fe-based alloy powder of the present invention can be produced, for example, by atomization. Examples of atomization methods include gas atomization, water atomization, and disk atomization. The use of gas atomization or disk atomization can prevent impurities from being mixed into the Fe-based alloy powder of the present invention. The gas atomization or disk atomization is preferably carried out in an inert gas atmosphere. Furthermore, the use of gas atomization can improve the mass productivity of the Fe-based alloy powder of the present invention.

[0021] The particle size distribution of the Fe-based alloy powder of the present invention is not particularly limited. The particle size distribution of the Fe-based alloy powder of the present invention can be adjusted taking into consideration the handling of the Fe-based alloy powder of the present invention. For example, Fe-based alloy powders having particle sizes equal to or smaller than a predetermined particle size can be selected by classification, and the selected Fe-based alloy powder can be used as the Fe-based alloy powder of the present invention. The predetermined particle size can be, for example, 150 μm or less. The lower limit of the predetermined particle size is not particularly limited as long as it is greater than 0 μm.

[0022] Hereinafter, the build-up layer formed using the Fe-based alloy powder of the present invention (hereinafter referred to as "the build-up layer of the present invention") and the method for forming the same will be described.

[0023] (Overlay Layer and Method for Forming the Same) The overlay layer of the present invention is formed on a substrate. By forming the overlay layer of the present invention on a substrate, a metal component is obtained that includes the substrate and the overlay layer of the present invention formed on the substrate. An intermediate layer may be present between the substrate and the overlay layer of the present invention, formed by mutual dissolution of a part of the substrate and a part of the overlay layer.

[0024] The cladding layer of the present invention can be formed on a substrate by a method including: (a) melting the Fe-based alloy powder of the present invention to obtain a molten metal; and (b) solidifying the molten metal obtained in step (a) on the substrate. A known method can be appropriately adopted as the method for forming the cladding layer, such as laser cladding. Various materials (metals) can be used as the substrate on which the cladding layer is formed. Examples of the substrate material include carbon steel, carbon tool steel, tool steel, and high-speed steel. Examples of heating means for melting the Fe-based alloy powder of the present invention include a gas combustion flame, plasma, and laser. The Fe-based alloy powder of the present invention can be heated before, after, or while being supplied to the substrate.

[0025] (Composition of the Weld Overlay) Since the weld overlay of the present invention is formed by melting an Fe-based alloy powder, the composition of the weld overlay of the present invention contains C, Si, Mn, Cr, Mo, and V, with the balance being Fe and unavoidable impurities, similar to the Fe-based alloy powder of the present invention. The contents (mass %) of C, Si, Mn, Cr, Mo, and V satisfy the conditions shown in the above formulas (1) to (6).

[0026] (Carbide Area Ratio of Overlay) The overlay of the present invention contains carbides. When a cross section of the overlay of the present invention is observed, circular or approximately circular carbides can be confirmed. In the present invention, circular or approximately circular carbides having a diameter (i.e., diameter) of 5 μm or less are referred to as "fine-grained carbides." In the present invention, the "diameter of carbide" refers to the circle-equivalent diameter of the carbide (the diameter of a circle equivalent to the area of ​​the carbide).

[0027] After polishing the cross section of the buildup layer of the present invention, the fine granular carbides can be identified by observing the microstructure that appears on the cross section. For example, the microstructure can be observed using a scanning electron microscope (SEM), and the fine granular carbides can be identified by image analysis based on color shading. Then, by identifying the fine granular carbides, the area of ​​the fine granular carbides that appears on the observed surface can be determined.

[0028] The carbide area ratio RA is defined based on the following formula (7).

[0029] In the above formula (7), RA is the carbide area ratio (%), Ao is the area of ​​the observation region in the cross section of the buildup layer, and Ac is the total area of ​​all fine granular carbides appearing within the observation surface. As can be seen from the above formula (7), the carbide area ratio RA is the ratio of the total area Ac of the fine granular carbides to the area Ao of the observation region. The area Ao can be calculated by setting the observation region.

[0030] Regarding the total area Ac, when only one fine-granular carbide appears within the observation surface, the area of ​​that one fine-granular carbide becomes the total area Ac. When multiple fine-granular carbides appear within the observation surface, the sum of the areas of all the fine-granular carbides becomes the total area Ac. When the entire fine-granular carbide appears within the observation surface, the area of ​​the entire fine-granular carbide can be found. On the other hand, when only a portion of the fine-granular carbide appears within the observation surface, the area of ​​that portion can be found.

[0031] In the buildup layer of the present invention, the carbide area ratio RA is 0.50% or more and 4.00% or less. The inclusion of fine-grained carbides in the buildup layer can improve the hardness and wear resistance of the buildup layer. To improve the hardness and wear resistance of the buildup layer, the carbide area ratio RA is set to 0.50% or more. The carbide area ratio RA is preferably 0.90% or more, more preferably 1.00% or more. On the other hand, if the carbide area ratio RA is too high, in other words, if fine-grained carbides are present in the buildup layer in excess, the toughness of the buildup layer will be adversely affected. Taking this into consideration, the carbide area ratio RA is set to 4.00% or less. The carbide area ratio RA is preferably 3.90% or less, more preferably 3.80% or less. Regarding the carbide area ratio RA, each of the above lower limits may be combined with any of the above upper limits.

[0032] Depending on the distribution of the fine granular carbides contained in the buildup layer, the area of ​​the fine granular carbides appearing in the cross section of the buildup layer may vary depending on the cross-sectional position of the buildup layer. Regardless of the cross-sectional position of the buildup layer, it is sufficient that the carbide area ratio RA is 0.50% or more and 4.00% or less.

[0033] The generation of fine granular carbides depends on the C content, the melting conditions of the Fe-based alloy powder when forming the buildup layer, and other factors. To achieve a carbide area ratio RA of 0.50% to 4.00%, the melting conditions of the Fe-based alloy powder when forming the buildup layer can be preset based on experiments, etc., in addition to the C content described above. For example, when forming the buildup layer using laser cladding, the carbide area ratio RA can be achieved by setting the laser output to 500 to 9000 W. The laser output is preferably 1000 to 7000 W, more preferably 1500 to 5000 W, even more preferably 2000 to 4000 W, and even more preferably 2500 to 3000 W. In one embodiment, the laser output is 2800 W. Regarding the laser output, each of the above lower limits may be combined with any of the above upper limits. Other conditions can be set as follows, for example: feed rate: 0.01 to 500 m / min, carrier gas: 1 to 100 L / min, shield gas: 1 to 100 L / min.

[0034] (Amount of soluble Cr in build-up layer) Cr is dissolved in the primary crystals of the build-up layer of the present invention. In the present invention, the "primary crystals" refer to the structure that is first formed when the Fe-based alloy powder of the present invention is melted and solidified. The dissolved Cr in the primary crystals contributes to improving the corrosion resistance of the build-up layer, thereby improving the corrosion resistance of the build-up layer. Therefore, the amount of dissolved Cr in the primary crystals is set to 5 mass% or more. The amount of dissolved Cr in the primary crystals is preferably 7 mass% or more. The amount of dissolved Cr in the primary crystals is preferably 25 mass% or less, more preferably 20 mass% or less. With regard to the amount of dissolved Cr in the primary crystals, the above-mentioned lower limit values ​​may be combined with any of the above-mentioned upper limit values.

[0035] When determining the amount of soluble Cr, first, the cross section of the buildup layer is observed to identify the primary crystals. When the cross section of the buildup layer is corroded using Villela's reagent (an alcohol solution containing 1 to 5 g of hydrochloric acid and 1 to 5 g of picric acid), the area corresponding to the primary crystals turns white, allowing the primary crystals to be identified. After identifying the primary crystals, the amount of Cr is detected at multiple detection points within the primary crystals using energy dispersive X-ray spectroscopy (EDS), and the average of the detected amounts of Cr is taken as the amount of soluble Cr. The multiple detection points are located at different positions within the primary crystals, and the number of detection points can be, for example, five or more.

[0036] The amount of soluble Cr depends on the Cr content in the Fe-based alloy powder, the melting conditions of the Fe-based alloy powder when forming the buildup layer, and other factors. To achieve a soluble Cr content of 5% by mass or more, the melting conditions of the Fe-based alloy powder when forming the buildup layer can be preset based on experiments, etc. For example, when forming the buildup layer using laser cladding, the amount of soluble Cr can be achieved by setting the laser output to 500 to 9000 W. The laser output is preferably 1000 to 7000 W, more preferably 1500 to 5000 W, even more preferably 2000 to 4000 W, and even more preferably 2500 to 3000 W. In one embodiment, the laser output is 2800 W. Regarding the laser output, each of the above lower limits may be combined with any of the above upper limits. Other conditions can be set as follows, for example: feed rate: 0.01 to 500 m / min, carrier gas: 1 to 100 L / min, shield gas: 1 to 100 L / min.

[0037] The build-up layer of the present invention can improve corrosion resistance and wear resistance.

[0038] Raw materials having the chemical compositions shown in Table 1 below were prepared for Examples 1 to 14 and Comparative Examples 1 to 16. The balance other than C, Si, Mn, Cr, Mo, and V is Fe and unavoidable impurities.

[0039]

[0040] The raw materials were placed in a refractory crucible and melted by high-frequency induction in an Ar gas atmosphere. The molten alloy was then tapped from a nozzle at the bottom of the crucible, and an Fe-based alloy powder was produced by gas atomization in a nitrogen gas atmosphere. That is, high-pressure argon gas was sprayed onto the molten alloy tapped from the nozzle, thereby refining the molten alloy and rapidly cooling it, thereby obtaining the Fe-based alloy powder.

[0041] The resulting Fe-based alloy powder was sorted to select those with particle sizes of 150 μm or less. Laser cladding was then performed on the substrate surface, where the Fe-based alloy powder (with particle sizes of 150 μm or less) was melted and solidified to form a cladding layer. The laser cladding conditions were: laser power: 2800 W, feed rate: 0.50 m / min, carrier gas: 5 L / min, and shield gas: 20 L / min. The substrate material was S45C.

[0042] (Evaluation of Carbide Area Ratio RA) The buildup layers (test pieces) obtained in each of Examples 1 to 14 and Comparative Examples 1 to 16 were cut in half and the cut surfaces were polished. The polished surfaces were corroded with Villela's solution, and the microstructure of the corroded surfaces was observed using a scanning electron microscope (SEM). Image analysis was performed on backscattered electron images of the observed areas to identify fine granular carbides based on the color shading. The area of ​​the fine granular carbides was then calculated, and the carbide area ratio RA was calculated based on the above formula (7). The calculation results of the carbide area ratio RA are shown in Table 2 below.

[0043] (Evaluation of the amount of soluble Cr) The buildup layers (test pieces) obtained in each of Examples 1 to 14 and Comparative Examples 1 to 16 were cut in half and the cut surfaces were polished. The polished surfaces were corroded with Vilela's solution, and then the amount of Cr was detected at five arbitrary detection points within the area that turned white due to corrosion (the area corresponding to the primary crystals) using energy dispersive X-ray spectroscopy (EDS). The average of the amounts of Cr detected at the five detection points was taken as the amount of soluble Cr. The measurement results of the amount of soluble Cr are shown in Table 2 below.

[0044] (Evaluation of Corrosion Resistance) The buildup layers obtained in Examples 1 to 14 and Comparative Examples 1 to 16 were subjected to a corrosion resistance test (salt spray test) in accordance with the provisions of JIS Z2371. After polishing the surface of the buildup layer, the polished surface was subjected to a salt spray test. The salt spray test conditions were a salt water concentration of 0.1 mass% and a test time of 16 hours.

[0045] After the salt spray test, the test surface sprayed with salt water was photographed, and the photographed image was analyzed to calculate the rust area ratio Rr represented by the following formula (8).

[0046] In the above formula (8), Rr is the rust area ratio (%), At is the area of ​​the entire test surface, and Ar is the total area of ​​the regions where rust has occurred. The areas At and Ar can be determined by analyzing the captured image. Here, if rust has occurred in multiple regions, the area Ar is the sum of the areas of the multiple regions where rust has occurred.

[0047] The corrosion resistance was evaluated as follows: no rust on the test surface was rated "A", the rust area ratio Rr was less than 5% was rated "B", and the rust area ratio Rr was 5% or more was rated "C". The evaluation results of corrosion resistance are shown in Table 2 below.

[0048] (Evaluation of Wear Resistance) The wear resistance of the buildup layers obtained in each of Examples 1 to 14 and Comparative Examples 1 to 16 was evaluated using an Ohkoshi rapid wear tester. The Ohkoshi rapid wear tester is an instrument that evaluates the width of wear scars by rotating (sliding) a ring-shaped pressure member against the surface of a plate-shaped test piece while applying a load. The test conditions for the Ohkoshi rapid wear tester were as follows: the pressure member was made of SCM420, the sliding distance was 200 m, the load was 6.3 kgf, and the rotation speed was 0.1 m / s.

[0049] In the evaluation of wear resistance, a test piece having a hard Cr plating coated on a substrate of S45C was subjected to a wear test using an Ohkoshi rapid wear tester, and the width of the wear scar (hereinafter referred to as the reference width) Wref was used as the reference value. Furthermore, the wear test was performed using the Ohkoshi rapid wear tester on the buildup layers obtained in each of Examples 1 to 14 and Comparative Examples 1 to 16, and the width of the wear scar We was measured. The ratio of the reference width Wref to the width We (hereinafter referred to as the wear width ratio) Rw was then calculated. The wear width ratio Rw is expressed by the following formula (9):

[0050]

[0051] In the above formula (9), Rw is the wear width ratio [-], Wref is the reference width described above, and We is the width of the wear scar in the evaluation object (Examples 1 to 14 and Comparative Examples 1 to 16). Here, when the width We is the reference width Wref, the wear width ratio Rw is 1.0. The smaller the width We is than the reference width Wref, the higher the wear width ratio Rw is than 1.0, indicating improved wear resistance. On the other hand, the larger the width We is than the reference width Wref, the lower the wear width ratio Rw is than 1.0, indicating a decrease in wear resistance. The evaluation results of wear resistance are shown in Table 2 below.

[0052]

[0053] The corrosion resistance of Examples 1 to 14 was evaluated as A. The wear width ratio Rw was 1.0 or more in all cases, confirming that the samples had excellent wear resistance.

[0054] On the other hand, for Comparative Examples 1 to 3 and 10 to 12, the corrosion resistance was evaluated as B or C, meaning that corrosion resistance could not be ensured, and the wear width ratio Rw was lower than 1.0, meaning that wear resistance could not be ensured. For Comparative Examples 4, 7, 15, and 16, the wear width ratio Rw was higher than 1.0, meaning that wear resistance was excellent, but the corrosion resistance was evaluated as C, meaning that corrosion resistance could not be ensured. For Comparative Examples 5, 6, 8, 9, 13, and 14, the corrosion resistance was evaluated as A, but the wear width ratio Rw was lower than 1.0, meaning that wear resistance could not be ensured.

Claims

1. An Fe-based alloy overlay layer containing C, Si, Mn, Cr, Mo and V, with the balance being Fe and unavoidable impurities, wherein the C, Si, Mn, Cr, Mo and V have the following respective contents: 1.60 mass%≦C≦3.50 mass% 0.20 mass%≦Si≦1.50 mass% 0.20 mass%≦Mn≦1.50 mass% 14.0 mass%≦Cr≦26.0 mass% 0.2 mass%≦Mo≦2.0 mass% 4.0 mass%≦V≦8.0 mass% In a cross section of the Fe-based alloy overlay layer, the ratio of the total area of ​​fine granular carbides having a diameter of 5 μm or less to the area of ​​the observation region is 0.50% or more and 4.00% or less, and the amount of Cr solid solution contained in the primary crystals of the Fe-based alloy overlay layer is 5 mass% or more.

2. The Fe-based alloy cladding layer according to claim 1, wherein the amount of Cr in solid solution is the average value of the amount of Cr detected at multiple points contained in the primary crystal.

3. A method for forming an Fe-based alloy buildup layer on a substrate, the method comprising: (a) a step of melting an Fe-based alloy powder to obtain a molten metal; and (b) a step of solidifying the molten metal on the substrate, wherein the Fe-based alloy powder contains C, Si, Mn, Cr, Mo, and V in the following contents, respectively, with the remainder consisting of Fe and unavoidable impurities: 1.60 mass%≦C≦3.50 mass% 0.20 mass%≦Si≦1.50 mass% 0.20 mass%≦Mn≦1.50 mass% 14.0 mass%≦Cr≦26.0 mass% 0.2 mass%≦Mo≦2.0 mass% 4.0 mass%≦V≦8.0 mass% the Fe-based alloy powder is melted under heat treatment conditions such that the ratio of the total area of ​​fine granular carbides having a diameter of 5 μm or less to the area of ​​an observation region in a cross section of the Fe-based alloy buildup layer is 0.50% or more and 4.00% or less, and the amount of Cr solid solution contained in the primary crystals of the Fe-based alloy buildup layer is 5 mass% or more.

4. The method according to claim 3, wherein the Fe-based alloy powder is melted using laser cladding with a laser power set to 500 to 9000 W.

5. The method according to claim 3 or 4, wherein the particle size of the Fe-based alloy powder is 150 μm or less.

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