Meat layer

Abstract

To provide the powders for build-up capable of preparing a build-up layer comprising both of high hardness and excellent toughness.SOLUTION: The powder for build-up is an alloy powder including Fe as a main component and comprises in mass%: C of more than 1.0% and 1.8% or less; (Si+Al) of 0.3-2.5%; Mn of 0.10-1.0%; Cr of 6.0-9.0%; (Mo+0.5W) of 2.0-6.0%; V of 1.0-4.0%; Co of 0.5-3.0%; and the balance of Fe with inevitable impurities.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention provides a weld overlay having high hardness and excellent toughness. Regarding do. [Background technology]

[0002] Conventionally, build-up welding methods using powdered welding materials have been used for repairing or surface modification of metal components. Known build-up welding methods include laser cladding and plasma powder build-up welding. The laser cladding method involves supplying powdered welding material to a high-power laser together with a carrier gas to heat and melt the material, and then colliding and depositing the molten material on the surface of the base metal, thereby forming a build-up layer on the surface of the base metal. The plasma powder build-up welding method involves supplying powdered welding material to a plasma arc generated between an electrode and a base metal using a carrier gas to heat and melt the material, and then colliding and depositing the molten material on the surface of the base metal, thereby forming a build-up layer on the surface of the base metal.

[0003] Patent Document 1 discloses a method for producing a wear-resistant tool material by forming a lower buildup layer on a substrate by laser cladding, and then forming an upper buildup layer directly on the lower buildup layer by laser cladding. The substrate is selected from SKD (alloy tool steel), SUJ (high carbon chromium bearing steel), SKH (high speed tool steel), etc., depending on the intended use of the tool material. The metal powders forming the lower and upper buildup layers have the same composition, and Fe-based SKH is used.

[0004] Patent Document 2 discloses a method for repairing a mold by forming a buildup on the mold surface by TIG welding using a welding material. The mold is made of JIS standard SKD61. The welding material is an alloy containing 0.15-0.30% C, 0.20-1.00% Si, 0.30-1.50% Mn, 3.6-6.0% Cr, 0.8-1.5% Mo, 0.10-0.80% V, and the balance being Fe and unavoidable elements.

[0005] Patent Document 3 discloses a metal component comprising a base material, which is a powder compact of an alloy primarily composed of Fe, and an overlay formed on the base material from a powder of the same components as the alloy. The overlay and base material of Patent Document 3 contain 0.03 to 2.6 mass% C, 0.05 to 1.0 mass% Si, 0.10 to 1.0 mass% Mn, and 3.0 to 30 mass% Cr, with the balance being Fe and unavoidable impurities. The overlay and base material of Patent Document 3 have a relationship such that the value expressed by (HB*BB) / (HA*BA) is 0.45 to 0.70 (where HA represents the hardness of the base material, BA represents the flexural strength of the base material, HB represents the hardness of the overlay, and BB represents the flexural strength of the overlay), and the overlay has excellent wear resistance and chipping resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-155155 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-245488 [Patent Document 3] Japanese Patent Publication No. 2020-070455 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, the lower build-up layer and the upper build-up layer are formed from build-up powder of the same composition, but this build-up powder is not designed with consideration given to the toughness of the build-up layer.

[0008] In Patent Document 2, the base metal and the welding material have the same or similar composition, but this composition does not take into consideration the toughness of the build-up layer made of the welding material.

[0009] The build-up powder of Patent Document 3 is considered to form a build-up layer excellent in chipping resistance and wear resistance. However, the build-up layer formed with the build-up powder of Patent Document 3 does not meet the condition that the flexural strength exceeds 2200 MPa when the hardness is 60 HRC or more, and is not considered to be able to achieve both toughness and a hardness of 60 HRC or more.

[0010] The present invention has been made in view of the above, and provides a cladding layer having both high hardness and excellent toughness. of It is intended to provide. [Means for solving the problem]

[0011] The build-up layer according to the present invention is A build-up layer formed by overlay welding an alloy powder mainly composed of Fe onto a metal member, The alloy is C: more than 1.0 mass% and 1.8 mass% or less; Si+Al: 0.3 mass% or more and 2.5 mass% or less, Mn: 0.1% by mass or more and 1.0% by mass or less, Cr: 6.0% by mass or more and 9.0% by mass or less, Mo+0.5W: 2.0 mass% or more and 6.0 mass% or less, V: 1.0% by mass or more and 4.0% by mass or less, and Co: 0.5% by mass or more and 3.0% by mass or less; The balance is Fe and unavoidable impurities, The buildup layer For each of five photographs of the surface of the sample cut out from the specimen, 50 primary carbides in the photograph were taken as the measurement object, and the major axis length and minor axis length of each of the primary carbides to be measured were measured to determine the aspect ratio. Primary carbides with an aspect ratio of 4.0 or less are counted of the object to be measured It is characterized by being more than 50% of the total primary carbides.

[0012]

[0013] Preferably, the above-mentioned overlaying The layer is The value Y expressed by the following formula 1 is between -1.0 and 1.5. Equation 1: Y={(0.06Cr+0.03Mo+0.06W+0.2V)-C} / (Si+Al) (In the above formula 1, Cr is Alloy represents the Cr content [mass %], and Mo represents the above Alloy represents the content of Mo [mass%], and V represents the above Alloy represents the V content [mass %], and C is the Alloy represents the C content [mass %], and Si represents the above Alloy represents the Si content [mass %], and Al represents the Alloy (Al content [mass%]) [Effects of the Invention]

[0014] According to the present invention, a build-up layer having both high hardness and excellent toughness is obtained. of can be provided. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows the configuration of samples used in examples of the present invention and comparative examples, where (a) is a plan view and (b) is a side view. [Figure 2] FIG. 2 shows an example of a scanning electron microscope photograph of the buildup layer in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The build-up powder according to the present invention is an alloy powder containing Fe as a main component. As the build-up welding method, a powder build-up welding method such as a laser cladding method or a plasma powder build-up welding method is used.

[0017] The alloy powder is based on Fe and contains C: more than 1.0 mass% and not more than 1.8 mass%, Si+Al: 0.3 mass% to 2.5 mass%, Mn: 0.10 mass% to 1.0 mass%, Cr: 6.0 mass% to 9.0 mass%, Mo+0.5W: 2.0 mass% to 6.0 mass%, V: 1.0 mass% to 4.0 mass%, and Co: 0.5 mass% to 3.0 mass%, with the remainder being Fe and unavoidable impurities.

[0018] [Iron (Fe)] The base element of this alloy powder is Fe. In other words, this alloy powder is an Fe-based alloy. Fe-based alloys have excellent strength and wear resistance. Powder made of this alloy is particularly suitable for repairing metal components.

[0019] [Carbon (C)] C dissolves in Fe. The dissolved C can contribute to improving hardness and strength. It also forms carbides with Cr, V, Mo, and W, contributing to improving wear resistance. From these viewpoints, the C content is preferably more than 1.0 mass% and not more than 1.8 mass%, and more preferably 1.1 mass% or more and 1.4 mass% or less.

[0020] [Silicon (Si) and Aluminum (Al)] Si and Al form a solid solution in Fe. Si and Al can contribute to strength, heat check resistance, and toughness. However, excessive addition of Si and Al deteriorates processing characteristics. From these viewpoints, the Si and Al content (Si + Al) is preferably 0.3 mass% or more and 2.5 mass% or less, more preferably 0.5 mass% or more and 2.0 mass% or less, and particularly preferably 0.6 mass% or more and 1.5 mass% or less. Note that the combination of Si and Al may contain only Si. Alternatively, only Al may be contained.

[0021] [Manganese (Mn)] Mn is a deoxidizing element. However, excessive addition of Mn deteriorates the workability required for shaping the buildup layer. From these viewpoints, the Mn content is preferably 0.10% by mass or more and 1.0% by mass or less, more preferably 0.15% by mass or more and 0.8% by mass or less, and particularly preferably 0.20% by mass or more and 0.5% by mass or less.

[0022] Chromium Cr forms carbides with C, improving wear resistance. It also dissolves in the matrix, improving corrosion resistance. However, excessive addition of Cr results in the formation of large carbides with a large aspect ratio, which not only reduces toughness and seizure resistance but also accelerates the progression of crevice corrosion starting around the carbides, thereby deteriorating corrosion resistance. From these perspectives, the Cr content is preferably 6.0% by mass or more and 9.0% by mass or less, and more preferably 6.5% by mass or more and 8.0% by mass or less.

[0023] [Molybdenum (Mo), Tungsten (W)] Mo and W form fine carbides (MC type) with C, contributing to improved strength. However, excessive addition of these elements forms large carbides, resulting in reduced toughness. Furthermore, W has the same effect as Mo, but to achieve the same effect, twice the amount of Mo is required. From these perspectives, the range of Mo+0.5W (in this formula, Mo represents the Mo content [mass%] in the cladding powder, and W represents the W content [mass%] in the cladding powder) is preferably 2.0 mass% or more and 6.0 mass% or less, and more preferably 3.0 mass% or more and 5.0 mass% or less.

[0024] [Vanadium(V)] Vanadium (V) forms fine carbides (VC) with C, contributing to improved wear resistance and hardness. However, excessive addition of these elements forms large carbides, resulting in a decrease in toughness. From these perspectives, the V content is preferably 1.0% by mass or more and 4.0% by mass or less, and more preferably 1.5% by mass or more and 3.5% by mass or less.

[0025] [Cobalt (Co)] Co, together with Fe, can be the base of the alloy. Co dissolves in Fe to increase hardenability and contribute to improving strength. The Co content is preferably 0.5% by mass or more and 3.0% by mass or less. However, since Co is an expensive element, the Co content is more preferably 1.0% by mass or more and 2.0% by mass or less.

[0026] [Method for producing powder for overlay welding] The above-mentioned powder for overlay welding can be produced by atomization, pulverization, etc. Examples of atomization methods include gas atomization, water atomization, and disk atomization. Gas atomization and disk atomization are preferred from the viewpoint of preventing impurities from being mixed into the alloy. Atomization in an inert gas atmosphere is preferred from the viewpoint of preventing impurities from being mixed into the alloy. Gas atomization is preferred from the viewpoint of mass productivity.

[0027] [Method for repairing metal components using build-up powder] A method for repairing a metal member with an overlay using the above-described overlay powder will be described. The metal member (i.e., base material) is produced by a melting method or a powder metallurgy method. Examples of such metal members include carbon steel, carbon tool steel, tool steel, and high-speed steel. Overlay welding is performed on the repaired portion of the metal member using the above-described overlay powder as a welding material, thereby forming an overlay layer. As the overlay welding method, a powder overlay welding method such as a laser cladding method or a plasma powder overlay welding method is used. Specifically, overlay welding is performed as follows: Particles of the overlay powder are given speed by a compressed gas or the like, and the accelerated particles are heated by a heating means. Examples of heating means include a gas combustion flame, plasma, and laser. The particles are heated to a molten or semi-molten state. The particles collide with the metal member and solidify, bonding the particles together. The particles also bond with the underlying metal member, forming a overlay layer on the surface of the metal member through this bonding. Heating may be performed after the particles collide with the metal member. Heating may be performed while the particles are in contact with the metal member, or a build-up layer may be formed on the preheated metal member.

[0028] As described above, primary carbides in a buildup layer formed on a metal component (base material) enhance the wear resistance of the buildup layer. On the other hand, excessive precipitation of primary carbides in the buildup layer results in the formation of primary carbides with a large aspect ratio, reducing the toughness of the buildup layer. As a result of diligent development in the present invention, it has been discovered that buildup layers formed using the buildup powder described above may contain many primary carbides with a small aspect ratio, and that these primary carbides have a favorable effect on the toughness of the buildup layer. Specifically, it has been found that buildup layers with an aspect ratio of 4.0 or less (50% or more by number) have excellent toughness. In other words, it has been found that buildup layers obtained from buildup powders have excellent toughness if the value X, expressed by the following equation 2, is 50 or greater.

[0029] Formula 2: X (%) = Number of primary carbides with aspect ratios of 4.0 or less / Total number of primary carbides × 100

[0030] One method for confirming the aspect ratio of primary carbides in the buildup layer is to take a photograph of the structure of the buildup layer with a scanning electron microscope (SEM) and then calculate the aspect ratio using image analysis software based on the obtained structural photograph.

[0031] Conventional overlay powders have been designed to form primary carbides by adding a large amount of carbon to ensure wear resistance. However, this approach can result in increased hardness and insufficient toughness because carbon also dissolves in the matrix. In response to this issue, extensive development has revealed that by optimizing the ratio of carbide-forming elements (e.g., C) to Si and Al in the overlay powder, the amount of primary carbides formed in the overlay layer made from the powder can be increased while the amount of dissolved carbon in the matrix can be reduced, resulting in high wear resistance and excellent toughness. Specifically, it has been found that if the value Y, expressed by the following formula 1, for the overlay powder is within a specific range, a overlay layer with high wear resistance and particularly excellent toughness can be formed. The value Y should be in the range of -1.0 to 1.5, preferably -0.5 to 0.5.

[0032] Formula 1: Y={(0.06Cr+0.03Mo+0.06W+0.2V)-C} / (Si+Al) (In the above formula 1, Cr represents the Cr content [% by mass] of the overlay welding powder, Mo represents the Mo content [% by mass] of the overlay welding powder, V represents the V content [% by mass] of the overlay welding powder, C represents the C content [% by mass] of the overlay welding powder, Si represents the Si content [% by mass] of the overlay welding powder, and Al represents the Al content [% by mass] of the overlay welding powder.) [Example]

[0033] The effects of the present invention will be clarified below by examples, but the present invention should not be construed as being limited based on the descriptions of these examples.

[0034] [1. Sample preparation] Raw materials having the prescribed compositions shown in Tables 1 to 4 were prepared. These raw materials were heated in a vacuum in an alumina crucible by high-frequency induction heating. The raw materials were melted by this heating to obtain a molten metal. The molten metal was dropped from a nozzle with a diameter of 5 mm located below the crucible. High-pressure argon gas was sprayed onto this molten metal to obtain 20 kg of alloy powder.

[0035] The produced alloy powder was sieved using a sieve of a size specified in "JIS-Z-8801" so that the particle size would be 150 to 45 μm, and used as powder for overlay welding.

[0036] [2. Fabrication of metal components] The metal parts used were S45C as specified in "JIS-G-405" and SKH40 as specified in "JIS-G-4403." Annealed steel was purchased commercially and cut into pieces 100 mm long, 100 mm wide, and 10 mm thick to form the metal parts (base material).

[0037] [3. Creating the build-up layer] Five kg of the prepared build-up powder was used to form a build-up layer on the prepared base material by laser cladding. Each sample thus prepared had a build-up layer 11 measuring 80 mm in length, 80 mm in width, and 15 mm in thickness formed on the base material 10, as shown in Figure 1(a)(b).

[0038] When creating the cladding layer, test cladding was performed with a laser output in the range of 2000W to 4000W and a feed rate in the range of 0.6mm / s to 1.2mm / s, and the area of ​​holes with a diameter of 30μm or more was 1mm 2 The power and feed rate were adjusted so that the number of holes per 1000 was less than five, and then the build-up was performed on the base material of the sample. Note that voids with a diameter of 30 μm or more may occur in the build-up layer due to the entrainment of atmospheric gas during build-up welding. These voids may cause chipping in the build-up layer or reduce the toughness of the build-up layer. Therefore, the area of ​​voids with a diameter of 30 μm or more in the build-up layer was determined to be 1 mm2. 2 The build-up conditions were adjusted so that the number of hits was less than five.

[0039] [4. Test Method] The samples of Examples 1 to 30 and Comparative Examples 1 to 30 obtained as described above were subjected to the following measurements and tests.

[0040] (Hardness measurement) The Vickers hardness of the buildup layer was measured in accordance with the provisions of JIS Z 2244. The Vickers hardness of the buildup layer was measured and evaluated from the area where the influence of dilution from the base material can be ignored, i.e., the range P4 shown in Figure 1(a)(b). The results are shown in Tables 1 to 4.

[0041] (Measurement of bending strength) A flexural test piece measuring 5 mm in width, 50 mm in length, and 3 mm in thickness was cut from the buildup layer. The flexural test piece was cut from a portion of the sample where the influence of dilution from the base material was negligible, i.e., from the area P3 shown in Figure 1(a)(b). The flexural strength of this flexural test piece was measured in accordance with the provisions of "JIS Z 2248." Five flexural strength measurements were performed, and the average values ​​are shown in Tables 1 to 4.

[0042] (Measurement of specific wear rate) To evaluate the wear resistance, an Ohkoshi wear test was conducted and the specific wear rate was calculated. The smaller the specific wear rate, the better the wear resistance. For the test, wear test specimens measuring 25 mm wide, 50 mm long, and 5 mm thick were cut from the buildup layer. The wear test specimens were cut from a portion of the sample where the effect of dilution from the base material was negligible, i.e., from the area P1 shown in Figures 1(a) and 1(b). The Ohkoshi wear test conditions were a wear distance of 200 m, a mating ring of SCM420, a final load of 123.4 N, and a wear speed of 10 m / s. The specific wear rate was calculated by measuring the width of the resulting wear scar. The results of this wear test are shown in Tables 1 to 4.

[0043] (Measurement of the aspect ratio of primary carbides) For each sample, a specimen was cut from the area P2 shown in Figures 1(a) and 1(b) and embedded in resin to prepare the specimen for observation. The surface of the specimen for observation was mirror-polished, and five-field photographs were taken using a scanning electron microscope. Figure 2 shows an example of a scanning electron microscope photograph of the overlay layer of the specimen, in which primary carbides appear as black particles in the matrix. Next, the major and minor axes of each of the 50 primary carbides in the photograph were measured, and the aspect ratio (major axis / minor axis) of each carbide was calculated for each of the five fields. Based on the aspect ratios of the carbides obtained in this way, the number of primary carbides with an aspect ratio of 4.0 or less was divided by the number of primary carbide samples (250 in this case) to calculate the value X. The value X represents the proportion (by number) of primary carbides with an aspect ratio of 4.0 or less among all primary carbides. The calculation results of the value X are shown in Tables 1 to 4.

[0044] [Table 1]

[0045] [Table 2]

[0046] [Table 3]

[0047] [Table 4]

[0048] [5. Evaluation Results] The overall evaluation of each sample based on the hardness and bending strength results is shown in Tables 1 to 4. The overall evaluation was based on the following evaluation criteria. S: The hardness of the buildup layer is 63HRC or more, the bending strength is 4000MPa or more, and the specific wear rate is 5.0 x 10 -8 mm 3 / Nmm or less. A: The hardness of the buildup layer is 63HRC or more, the bending strength is 3000MPa or more and less than 4000MPa, and the specific wear rate is 5.0 x 10 -8 mm 3 / Nmm or less. B: The hardness of the buildup layer is 63HRC or more, the bending strength is 2000MPa or more and less than 3000MPa, and the specific wear rate is 5.0 x 10 -8 mm 3 / Nmm or less. F: The hardness of the buildup layer is less than 63HRC or the bending strength is less than 2000MPa, or the specific wear amount is 5.0 x 10 -8 mm 3 / Nmm or more (Note that those with a hardness of less than 63HRC were judged to be insufficient for use as a build-up layer, and no bending test was carried out).

[0049] As shown in Tables 1 and 2, the samples of Examples 1 to 5 and 16 to 20 have the following characteristics (a) to (c). (a) The sample build-up powder is a build-up powder whose main component is Fe, and contains C: more than 1.0 mass% and not more than 1.8 mass%, Si + Al: 0.3 mass% to 2.5 mass%, Mn: 0.10 mass% to 1.0 mass%, Cr: 6.0 mass% to 9.0 mass%, Mo + 0.5W: 2.0 mass% to 6.0 mass%, V: 1.0 mass% to 4.0 mass%, and Co: 0.5 mass% to 3.0 mass%, with the remainder being Fe and unavoidable impurities. (b) The build-up layer of the sample has a hardness of 63HRC or more and a bending strength of 2000MPa to 3000MPa. (c) The buildup layer of the sample had a specific wear rate of 5.0 × 10 -8 mm 3 / Nmm or less.

[0050] From the above characteristics (b) and (c), it can be said that the build-up layers of the samples of Examples 1 to 5 and 16 to 20 have excellent toughness in addition to high hardness and excellent wear resistance.

[0051] Furthermore, the samples of Examples 6 to 10 and 21 to 25 shown in Tables 1 and 2 have the following characteristics (b') and (d) in addition to the above characteristics (a) and (c). (b') The build-up layer of the sample has a hardness of 63HRC or more and a bending strength of 3000MPa to 4000MPa. (d) The value X (see Equation 2) is 50(%) or more.

[0052] The buildup layers of the samples of Examples 6 to 10 and 21 to 25 have both the above characteristics (b') and (c), and therefore can be said to have even better toughness while maintaining high hardness and excellent wear resistance properties compared to the samples of Examples 1 to 5 and 16 to 20, which have the above characteristics (b) and (c).

[0053] Furthermore, the samples of Examples 11 to 15 and 26 to 30 shown in Tables 1 and 2 have the following characteristics (b") and (e) in addition to the above characteristics (a), (c), and (d). The hardness of the cladding layer of the (b") sample is 63HRC, and the flexural strength is over 4000MPa. (e) The value Y (see Equation 1) is between −1.0 and 1.5.

[0054] The buildup layers of the samples of Examples 6 to 10 and 21 to 25 have both the above characteristics (b") and (c), and therefore can be said to have even better toughness while maintaining high hardness and excellent wear resistance properties compared to the samples of Examples 6 to 10 and 21 to 25 which have the above characteristics (b') and (c).

[0055] The samples of Comparative Examples 1 to 30 shown in Tables 3 and 4 have a buildup layer hardness of 63 HRC or more, but their flexural strength is less than 2000 MPa. Furthermore, some of the samples of Comparative Examples 1 to 30 have a buildup layer hardness of less than 63 HRC, and are clearly inferior in toughness to the samples of Examples 1 to 30. In addition, the samples of Comparative Examples 1 to 30 have a specific wear rate of 5.0 × 10 -8 mm 3 Some samples had a wear resistance greater than 1 / Nmm, and some samples had poorer wear resistance than the samples of Examples 1 to 30.

[0056] From the above, it has become clear that the powder for overlay welding according to the present invention can provide an overlay layer that has high hardness, excellent wear resistance, and also excellent toughness.

Claims

1. A build-up layer formed by build-up welding an alloy powder mainly composed of Fe onto a metal member, The alloy is C: more than 1.0 mass% and not more than 1.8 mass%; Si + Al: 0.3% by mass or more and 2.5% by mass or less, Mn: 0.10% by mass or more and 1.0% by mass or less, Cr: 6.0% by mass or more and 9.0% by mass or less, Mo+0.5W: 2.0 mass% or more and 6.0 mass% or less, V: 1.0% by mass or more and 4.0% by mass or less, and Co: 0.5% by mass or more and 3.0% by mass or less; The balance is Fe and unavoidable impurities, For each of five field photographs of the surface of the sample cut out from the buildup layer, 50 primary carbides in the photographs are taken as measurement objects, and when the major axis length and minor axis length of each of the primary carbides to be measured are measured to determine the aspect ratio, primary carbides having an aspect ratio of 4.0 or less account for 50% or more of all primary carbides to be measured on a number basis. Overlay layer.

2. The buildup layer according to claim 1, wherein the value Y represented by the following formula 1 is -1.0 or more and 1.5 or less. Formula 1: Y={(0.06Cr+0.03Mo+0.06W+0.2V)-C} / (Si+Al) (In the above formula 1, Cr represents the Cr content [% by mass] of the alloy, Mo represents the Mo content [% by mass] of the alloy, W represents the W content [% by mass] of the alloy, V represents the V content [% by mass] of the alloy, C represents the C content [% by mass] of the alloy, Si represents the Si content [% by mass] of the alloy, and Al represents the Al content [% by mass] of the alloy.)

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