Regeneration method

Abstract

According to the present invention, a repair and restoration method can be provided. Specifically, according to the present invention, a repair and restoration method can be provided that ensures excellent weldability and mechanical properties even after a heat treatment step.

Description

Technology Field

[0001] The present invention relates to a regeneration repair method, and more specifically, to a regeneration repair method that includes a heat treatment step and can secure mechanical properties after regeneration repair. Background Technology

[0002] Methods known as restoration methods include Direct Energy Deposition (DED) or Gas Tungsten Arc Welding (GTAW).

[0003] GTAW is a widely used method in current industries. It involves supplying filler metal to an arc to melt and shape the object, enabling repair by simultaneously melting the base metal and the powder. However, since the repair is performed manually by the welder, there is a problem where the results vary depending on the operator's skill level.

[0004] The DED method is known as a 3D printing method that manufactures a shape by melting repair powder with a high-temperature laser. Accordingly, repair is possible by melting only the powder without melting the metal base material of the object to be repaired. This DED method is not well known in the metal base material repair industry.

[0005] However, since the DED method requires a heat treatment process in the final stage of regeneration and repair, there were no circumstances to consider such a process for conventional regeneration and repair powders, whose mechanical properties deteriorate after heat treatment.

[0006] For example, Alloy 625, which has excellent weldability, is widely used in various industries. However, Alloy 625 has the disadvantage that its mechanical properties deteriorate after heat treatment following welding due to its solid solution strengthening characteristic.

[0007] In other words, weldability and mechanical properties have an inverse relationship, so conventionally, repairs were performed using methods such as GTAW, laser, and plasma welding with alloy 625, which is easy to weld, but there was a problem with cracks such as fine cracks or fissures occurring at high temperatures.

[0008] Prior art patent document 0001 discloses a method for repair and restoration. Prior art patent 0001 addresses the difficulties in maintaining surface temperature, the difficulties in maintaining inert gas shielding, and the physical difficulties of the worker in hot box welding using the conventional GTAW process. However, it does not disclose how to solve the problem of reduced strength after heat treatment.

[0009] There is a need to provide a new repair method capable of securing mechanical properties using the DED method, which includes a heat treatment step. The problem to be solved

[0010] The purpose of the present invention is to provide a regeneration and repair method.

[0011] Specifically, the purpose of the present invention is to provide a repair and restoration method that can ensure excellent weldability and mechanical properties even after a heat treatment step.

[0012] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0013] A regeneration repair method according to one embodiment of the present invention comprises: a step of preparing a metal base material requiring regeneration repair; a step of injecting a regeneration repair powder into a regeneration repair portion; a step of melting the powder onto the base material through a laser; and a heat treatment step performed in three steps while lowering the temperature.

[0014] Additionally, the heat treatment step may include a first step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 1000℃ or more and 1300℃ or less, a second step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 900℃ or more and 1100℃ or less, and a third step of performing heat treatment for 20 hours or more and 25 hours in a temperature range of 700℃ or more and 900℃ or less.

[0015] In addition, in the step of melting the powder with a laser, the laser power of the laser may be in the range of 300W or more and 550W or less.

[0016] In addition, in the step of melting the powder with a laser, the scan speed of the laser may be in the range of 650 mm / s or more and 750 mm / s or less.

[0017] In addition, the above-mentioned regenerative powder may contain Cr 20 wt% or more and 23 wt% or less, Co 18 wt% or more and 20 wt% or less, Ti 3 wt% or more and 5 wt% or less, Al 1 wt% or more and 3 wt% or less, C 0.01 wt% or more and 0.2 wt% or less, B 0.001 wt% or more and 0.01 wt% or less, the remainder being Ni and unavoidable impurities.

[0018] In addition, the above-mentioned regenerative powder may further include one or more of W, Nb, Ta, or Zr in a range of 0.005% by weight or more and 3% by weight or less.

[0019] In addition, the above-mentioned regenerative powder may further contain Fe 0.5 wt% or less, Si or S 0.05 wt% or less, or P, N, Pb, Bi, Ag or O 0.001 wt% or less.

[0020] In addition, the rate of change in tensile strength after heat treatment according to Equation 3 below may be -5.5% or more.

[0021] [Equation 3]

[0022] {(AT - BT) / AT} × 100

[0023] In Equation 3, AT is the tensile strength of the base material that has been regenerated and repaired after heat treatment, and BT is the tensile strength of the base material before heat treatment.

[0024] In addition, the rate of change in yield strength after heat treatment according to Equation 4 below may be 0% or more.

[0025] [Equation 4]

[0026] {(CT - DT) / CT} × 100

[0027] CT is the yield strength of the base material that has been regenerated and repaired after heat treatment, and DT is the yield strength of the base material before heat treatment. Effects of the invention

[0028] According to the present invention, a regeneration and repair method can be provided.

[0029] Specifically, according to the present invention, a repair and restoration method can be provided that ensures excellent weldability and mechanical properties even after a heat treatment step.

[0030] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0031] FIG. 1 is an exemplary drawing illustrating a repair and restoration method of the present invention. FIG. 2 is a drawing showing the specifications of a specimen of the present invention. Figure 3 is a stress strain graph before and after heat treatment of the present invention. FIG. 4 is a drawing showing a specimen of the present invention arbitrarily cut. FIG. 5 is a diagram showing the fracture location of one embodiment of the present invention. Specific details for implementing the invention

[0032] The present invention is described in detail below so that those skilled in the art can easily implement it. However, the present invention is not limited or restricted by the following embodiments.

[0033] Terms such as "include" or "have" are intended to specify the existence of the steps, actions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, components, or combinations thereof.

[0034] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0035] In addition, among the physical properties mentioned in this specification, those affected by the measurement temperature are properties measured at room temperature unless specifically otherwise specified. The term "room temperature" refers to a natural temperature that has not been artificially heated or cooled, and may, for example, mean a temperature of about 23°C or about 25°C. In this specification, the unit of temperature is Celsius (°C) unless specifically otherwise specified.

[0036] Among the physical properties mentioned in this specification, those affected by the measured pressure are properties measured at atmospheric pressure, unless otherwise specifically defined. The term atmospheric pressure refers to natural pressure that has not been specifically pressurized or depressurized, and may refer to any pressure within the range of approximately 730 mmHg to 790 mmHg.

[0037] Among the physical properties mentioned in this specification, the physical properties affected by the measured humidity are physical properties measured at standard humidity, unless specifically otherwise defined. Standard humidity may refer to relative humidity (RH%) of about 55% or 60%.

[0038] The present invention relates to a repair and restoration method.

[0039] The regeneration repair method of the present invention may be a regeneration repair method comprising the steps of preparing a metal base material requiring regeneration repair, injecting a regeneration repair powder into a regeneration repair portion, melting the powder onto the metal base material through a laser, and performing a heat treatment step in three steps while lowering the temperature.

[0040] The step of preparing the metal base material requiring regeneration is not particularly limited. For example, the metal base material may be a nickel-based superalloy.

[0041] The step of injecting the regeneration repair powder into the above-mentioned regeneration repair part may be performed simultaneously with or sequentially with the step of melting the powder onto the metal base material using a laser.

[0042] Figure 1 is a diagram showing the melting of powder while injecting it through a laser in the regeneration and repair method of the present invention.

[0043] The above laser is intended to inject powder onto a metal substrate while melting it, and the laser power and scan speed can be considered depending on the metal substrate or the regeneration powder.

[0044] More specifically, the laser power of the present invention may be in the range of 300W or more and 550W or less, and the scan speed may be in the range of 650mm / s or more and 750mm / s or less. If the laser power or scan speed does not fall within the above-described range, a small amount of powder may not melt, which may result in a cost in securing strength, and if it exceeds the upper limit of the above-described range, it may cause a problem of melting the base material. Therefore, the laser power or scan speed can be controlled within the above-described range.

[0045] It may include a first step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 1000℃ or more and 1300℃ or less, a second step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 900℃ or more and 1100℃ or less, and a third step of performing heat treatment for 20 hours or more and 25 hours in a temperature range of 700℃ or more and 900℃ or less.

[0046] The first step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 1000℃ or more and 1300℃ or less may be more specifically a step of performing heat treatment for a time of 100 minutes or more and 120 minutes or less in a temperature range of 1100℃ or more and 120℃ or less.

[0047] The second step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 900℃ or more and 1100℃ or less may be more specifically a step of performing heat treatment for a time of 100 minutes or more and 120 minutes or less in a temperature range of 1000℃ or more and 1100℃ or less.

[0048] In addition, the third step of performing heat treatment for 20 hours or more and 25 hours in a temperature range of 700°C or higher and 900°C or lower may be more specifically a step of performing heat treatment for 22 hours or more and 24 hours or less in a temperature range of 800°C or higher and 850°C or lower.

[0049] By sequentially lowering the temperatures of the first, second, and third stages as described above, the molten repair powder can be combined with the metal base material to secure the mechanical strength of the repaired base material. In addition, if the temperature is lowered rapidly after repair, cracks such as cracks may occur in the repaired part due to sudden temperature changes; therefore, mechanical properties can be secured even after heat treatment through the temperature and time within the range described above.

[0050] For example, if the temperature or time from the first to the third step exceeds the upper limit described above, problems may occur such as the regenerated repair powder being remelted or a part of the base material melting, and if the temperature or time does not fall below the lower limit described above, the effect of gradually lowering the temperature may be insufficient. Therefore, it is desirable that the heat treatment step be performed sequentially as a three-step heat treatment process at the temperature and time described above.

[0051] The repair method of the present invention is different from the gas tungsten arc welding (GTAW) method commonly used in the industry, and the major distinction of the repair method is the Direct energy deposition (DED) method.

[0052] In particular, since the DED method requires a heat treatment process during the regeneration and repair process, there were no circumstances to consider such a process with conventional regeneration and repair powders, whose mechanical properties deteriorate after heat treatment.

[0053] In other words, the DED method, which includes a heat treatment step in the final stage, was not preferred in conventional repair and restoration processes.

[0054] The present invention can secure excellent mechanical properties even after performing the heat treatment step following the injection and melting of the regenerative repair powder.

[0055] The regenerative repair powder injected into the regenerative repair part of the present invention, or the powder melted onto the base material through a laser, is not particularly limited. Regardless of the type of regenerative repair powder, the regenerative repair method of the present invention allows for the selection of an appropriate regenerative repair powder depending on the material of the metal base material.

[0056] For example, the regenerative repair powder may be a powder containing 20 wt% or more and 23 wt% or less of Cr, 18 wt% or more and 20 wt% or less of Co, 3 wt% or more and 5 wt% or less of Ti, 1 wt% or more and 3 wt% or less of Al, 0.01 wt% or more and 0.2 wt% or less of C, 0.001 wt% or more and 0.01 wt% or less of B, and the remainder being Ni and unavoidable impurities.

[0057] Cr (chromium) is an element that plays an important role in securing corrosion resistance, oxidation resistance, and mechanical strength after heat treatment in the present invention. The lower limit of the Cr content may be approximately 20 wt%, 21 wt%, or 22 wt%, and the upper limit may be approximately 23 wt%, 22.9 wt%, or 22.8 wt%. If the Cr content falls below the aforementioned lower limit, it is difficult to secure the effect of maintaining strength after heat treatment. Conversely, if the Cr content exceeds the aforementioned upper limit, an unstable phase may be excessively formed, which may reduce toughness and elongation. Therefore, the Cr content may be within the range of being above or above the aforementioned lower limit, or below or less than the aforementioned upper limit.

[0058] Cobalt (Co) can serve to form the basic matrix of the powder in the present invention. Additionally, Co plays a role in ensuring mechanical strength and ductility at high temperatures. The lower limit of the Co content may be approximately 18 wt%, 18.5 wt%, or 19 wt%, and the upper limit may be approximately 20 wt% or 19.5 wt%. If the Co content falls below the aforementioned lower limit, the stability of the substrate may be reduced, which may lead to a decrease in mechanical strength and / or heat resistance. Conversely, if the Co content exceeds the aforementioned upper limit, the brittleness of the regenerated repair part may increase due to excessive grain growth. Therefore, the Co content may be within a range greater than or exceeding the aforementioned lower limit, or less than or below the aforementioned upper limit.

[0059] In the present invention, Ti (titanium) can play a role in improving ductility and tensile strength through grain refinement. Ti may also secure additional strength through a precipitation strengthening effect by forming fine precipitates during heat treatment. The lower limit of the Ti content may be approximately 3 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, or 3.4 wt%, and the upper limit may be approximately 5 wt%, 4.5 wt%, 4 wt%, or 3.5 wt%. If the Ti content falls below the aforementioned lower limit, the precipitation strengthening effect may not be sufficient, and mechanical strength and heat resistance may decrease. Conversely, if the Ti content exceeds the aforementioned upper limit, excessive precipitates may lead to heterogeneous phases or excessive hardening, which may increase the brittleness of the regenerated repair part. Therefore, the Ti content may be within a range greater than or exceeding the aforementioned lower limit, or less than or below the aforementioned upper limit.

[0060] Al (aluminum), like Ti, can play a role in improving ductility and tensile strength through grain refinement in the present invention. Al can also secure additional strength through a precipitation strengthening effect by forming fine precipitates during heat treatment. The lower limit of the Al content may be approximately 1 wt%, 1.2 wt%, 1.4 wt%, or 1.6 wt%, and the upper limit may be approximately 3 wt%, 2.5 wt%, 2 wt%, or 1.8 wt%. If the Al content falls below the aforementioned lower limit, the precipitation strengthening effect is insufficient, which may result in reduced mechanical strength and heat resistance. Conversely, if the Al content exceeds the aforementioned upper limit, excessive precipitates may lead to heterogeneous phases or excessive hardening, which may increase the brittleness of the regenerated repair part. Therefore, the Ti content may be within a range greater than or greater than the aforementioned lower limit, or less than or less than the aforementioned upper limit.

[0061] In the present invention, C (carbon) can play a role in improving strength by forming fine carbide particles even in small amounts, thereby providing a precipitation strengthening effect. The lower limit of the C content may be approximately 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, or 0.06 wt%, and the upper limit may be approximately 0.3 wt%, 0.25 wt%, 0.2 wt%, 0.15 wt%, 0.1 wt%, or 0.08 wt%. If the C content falls below the aforementioned lower limit, the strength improvement effect is insufficient, and the improvement of mechanical strength may be limited. Conversely, if the C content exceeds the aforementioned upper limit, excessive carbide formation may increase the brittleness of the regenerated repair part and cause cracks. Therefore, the C content may be within a range greater than or exceeding the aforementioned lower limit, or less than or below the aforementioned upper limit.

[0062] In the present invention, B (Boron) can play a role in strengthening the grain interface to improve resistance to thermal deformation and cracking during regeneration repair. The lower limit of the B content may be approximately 0.001 wt%, 0.002 wt%, 0.003 wt%, or 0.004 wt%, and the upper limit may be approximately 0.01 wt%, 0.009 wt%, 0.008 wt%, 0.007 wt%, 0.006 wt%, or 0.005 wt%. If the B content falls below the aforementioned lower limit, the effect of grain strengthening is insufficient, and brittleness may increase after regeneration repair. Conversely, if the B content exceeds the aforementioned upper limit, localized concentration may occur, leading to problems of excessive brittleness. Therefore, the B content may be within the range of being above or above the aforementioned lower limit, or below or less than the aforementioned upper limit.

[0063] The remainder of the powder composition of the present invention is Ni and unavoidable impurities.

[0064] In the present invention, Ni plays a role in forming the basic matrix of the powder, and since mechanical strength and ductility can be secured at high temperatures, the remainder of the powder, excluding inevitable impurities, may be Ni.

[0065] In addition, for example, the regenerative repair powder may further contain one or more of W, Nb, Ta, or Zr in a range of 0.005% by weight or more and 3% by weight or less. When the powder further contains one or more of W, Nb, Ta, or Zr, it may be included in place of Ni.

[0066] When additional W (tungsten) is included, excellent heat resistance and strength can be secured. Tungsten can contribute to maintaining tensile strength and yield strength even after heat treatment. When additional W is included, the lower limit of the desirable W content may be approximately 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2.0 wt%, and the upper limit may be approximately 3 wt%, 2.8 wt%, 2.6 wt%, 2.4 wt%, or 2.2 wt%. When additional W is included, if the W content does not fall below the lower limit, it may be difficult to secure the desired strength and creep resistance. Conversely, when additional W is included, if the W content exceeds the aforementioned upper limit, an unstable phase may be formed during heat treatment, which may increase the brittleness of the regenerated repair part or cause a decrease in elongation. Accordingly, if W is further included, it may be included in a range of 0.005% by weight or more and 3% by weight or less, or preferably within a range greater than or greater than the lower limit described above and less than or equal to the upper limit described above.

[0067] If Nb (niobium) or Ta (tantalum) is further included, fine carbides can be formed to aid in the precipitation strengthening effect. Niobium or tantalum can contribute to maintaining tensile strength and yield strength even after heat treatment. If Nb or Ta is further included, the lower limit of the preferred content of Nb or Ta may be approximately 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, and the upper limit may be approximately 2 wt%, 1.8 wt%, 1.6 wt%, 1.4 wt%, 1.2 wt%, or 1 wt%. If Nb or Ta is further included and the content of Nb or Ta does not fall below the aforementioned lower limit, it may be difficult to secure the desired strength for the precipitation strengthening effect. In contrast, if Nb or Ta is further included, and the content of Nb or Ta exceeds the upper limit described above, the surface may become rough and durability may be compromised, or excessive carbide may be formed, which may reduce toughness and weldability during repair. Therefore, if Nb or Ta is further included, it may be included in a range of 0.005 wt% or more and 3 wt% or less, or preferably within a range of above or above the lower limit described above and below or less than the upper limit described above.

[0068] When Zr (zirconium) is additionally included, the microstructure grain size can be finely controlled, allowing the microstructure to be maintained even after regeneration and repair, thereby improving long-term fatigue properties. When Zr is additionally included, the lower limit of the desirable Zr content may be approximately 0.005 wt%, 0.006 wt%, 0.007 wt%, or 0.008 wt%, and the upper limit may be approximately 0.1 wt%, 0.05 wt%, 0.01 wt%, or 0.009 wt%. When Zr is additionally included, if the Zr content falls below the aforementioned lower limit, the grain refinement effect is insufficient, and microstructural stability may be inferior during heat treatment. Conversely, when Zr is additionally included, if the Zr content exceeds the aforementioned upper limit, unnecessary intermetallic compounds may be formed, which may lead to a decrease in ductility and toughness. Accordingly, if Zr is further included, it may be included in a range of 0.005% by weight or more and 3% by weight or less, or preferably within a range greater than or greater than the lower limit described above and less than or equal to the upper limit described above.

[0069] In addition, for example, the regenerative repair powder is not particularly limited if it is an impurity known in the art of the present invention, such as Fe, Si, S, P, N, Pb, Bi, Ag, or O.

[0070] Fe (iron) is an element that must be removed or minimized during the regeneration and repair process, and even if it is included as an impurity, its content may be 0.5 wt% or less, 0.4 wt% or less, 0.3 wt% or less, 0.2 wt% or less, or 0.15 wt% or less.

[0071] Likewise, Si (silicon) and S (sulfur) are elements that must be removed or minimized during the regeneration and repair process, and even if included as impurities, their content may be 0.05 wt% or less, 0.04 wt% or less, 0.03 wt% or less, 0.02 wt% or less, 0.01 wt% or less, or 0.005 wt% or less.

[0072] In addition, P (phosphorus), N (nitrogen), Pb (lead), Bi (bismuth), Ag (silver), or O (oxygen) are elements that must be removed or minimized during the regeneration and repair process, and even if included as impurities, their content may be 0.001% by weight or less or 0.0005% by weight or less.

[0073] The content of the above impurities, particularly P or S, must be minimized because they play a role in causing brittleness during the regeneration and repair process; similarly, the content of Si or Fe must also be minimized because they play a role in causing defects during the regeneration and repair process due to issues such as the formation of unnecessary phases.

[0074] According to the regeneration and repair method of the present invention, results can be secured regardless of the operator's skill level, and excellent mechanical properties can be secured even after heat treatment. These mechanical properties may be expressed as yield strength, tensile strength, and / or elongation.

[0075] In the regeneration repair method of the present invention, the yield strength that can be secured before heat treatment may be 640 MPa or more, 660 MPa or more, 680 MPa or more, 700 MPa or more, 720 MPa or more, 740 MPa or more, 760 MPa or more, 780 MPa or more, 800 MPa or more, 810 MPa or more, 820 MPa or more, or 830 MPa or more. In addition, although the upper limit is not particularly limited, it may be 1,000 MPa or less, 950 MPa or less, 900 MPa or less, or 890 MPa or less.

[0076] In the regeneration repair method of the present invention, the tensile strength that can be secured before heat treatment may be approximately 820 MPa or more, 840 MPa or more, 860 MPa or more, 880 MPa or more, 900 MPa or more, 920 MPa or more, 940 MPa or more, 960 MPa or more, 980 MPa or more, 1,000 MPa or more, 1020 MPa or more, 1040 MPa or more, 1060 MPa or more, or 1080 MPa or more. In addition, although the upper limit is not particularly limited, it may be approximately 2,000 MPa or less, 1,500 MPa or less, 1,400 MPa or less, or 1,300 MPa or less.

[0077] In addition, in the regeneration repair method of the present invention, the elongation that can be secured before heat treatment may be 50% or less, 45% or less, 40% or less, or 35% or less.

[0078] Here, the mechanical properties that can be secured before heat treatment are the mechanical properties after injecting and melting the regenerative repair powder onto the base material, and may refer to the mechanical properties of the base material on which the regenerative repair method has been performed up to the immediate prior to the heat treatment step.

[0079] In addition, in the regeneration repair method of the present invention, the tensile strength that can be secured before heat treatment can satisfy the following Equation 1.

[0080] [Equation 1]

[0081] {(A - B) / A} × 100

[0082] In Equation 1, A is the tensile strength of the base material that has been repaired after repair, and B is the tensile strength of the base material that requires repair.

[0083] The lower limit of Equation 1 may be approximately -5.5%, -4.5%, -3.5%, -2.5%, -1.5%, -0.5%, or 0%, and the upper limit may be approximately 100%, 80%, 60%, 40%, 30%, or 20%, although it is not specifically limited. The value of Equation 1 may be in a range greater than or equal to the lower limit described above.

[0084] That is, Equation 1 represents the rate of change of tensile strength, and the meaning that the value of Equation 1 is within the range described above is that the tensile strength of the base material on which the regeneration repair method is performed up to the heat treatment step, compared to the base material requiring regeneration repair, decreases by 5.5% or less, or the tensile strength increases. In other words, the regeneration repair method of the present invention can secure the effect of having a small rate of decrease in tensile strength compared to the existing base material after regeneration repair, or even an increase in tensile strength, even before heat treatment.

[0085] In the regeneration repair method of the present invention, the yield strength that can be secured before heat treatment can satisfy the following Equation 2.

[0086] [Equation 2]

[0087] {(C - D) / C} × 100

[0088] In Equation 2, C is the yield strength of the base material that has been repaired after repair, and D is the yield strength of the base material that requires repair.

[0089] The lower limit of Equation 2 may be approximately 0%, 0.5%, or 0.8%, and the upper limit may be approximately 100%, 80%, 60%, 40%, 30%, 20%, 10%, or 5%, although it is not specifically limited. The value of Equation 2 may be in a range greater than or equal to the lower limit described above.

[0090] That is, Equation 2 represents the rate of change of yield strength, and the meaning that the value of Equation 2 is within the range described above is that the yield strength of the base material on which the regeneration repair method has been performed up to the heat treatment step increases compared to the base material requiring regeneration repair. In other words, the regeneration repair method of the present invention can secure the effect of increasing the yield strength compared to the existing base material after regeneration repair, even before heat treatment.

[0091] In addition, the regeneration and repair method of the present invention can secure excellent mechanical properties even after the heat treatment step.

[0092] The yield strength that can be obtained after heat treatment with the regenerative repair powder of the present invention may be 820 MPa or more, 830 MPa or more, 840 MPa or more, 850 MPa or more, or 860 MPa or more. In addition, although the upper limit is not particularly limited, it may be 1,000 MPa or less, 950 MPa or less, 900 MPa or less, or 890 MPa or less.

[0093] In addition, the tensile strength that can be secured after heat treatment with the regenerative repair powder of the present invention may be 1100 MPa or more, 1150 MPa or more, 1200 MPa or more, 1250 MPa or more, or 1300 MPa or more. In addition, although the upper limit is not particularly limited, it may be 2,000 MPa or less, 1,500 MPa or less, 1,400 MPa or less, or 1,300 MPa or less.

[0094] In addition, the elongation that can be obtained after heat treatment by the method of the present invention may be 30% or less, 25% or less, 20% or less, or 15% or less.

[0095] In addition, the tensile strength that can be secured after heat treatment of the present invention can satisfy the following Equation 3.

[0096] [Equation 3]

[0097] {(AT - BT) / AT} × 100

[0098] In Equation 3, AT is the tensile strength of the base material that has been regenerated and repaired after heat treatment, and BT is the tensile strength of the base material before heat treatment.

[0099] The lower limit of Equation 3 may be approximately -5.5%, -4.5%, -3.5%, -2.5%, -1.5%, -0.5%, or 0%, and the upper limit may be approximately 100%, 80%, 60%, 40%, 30%, or 20%, although it is not specifically limited. The value of Equation 3 may be in the range above or above the aforementioned lower limit.

[0100] That is, Equation 3 represents the rate of change of tensile strength, and the meaning that the value of Equation 3 is within the range described above is that, after the step of melting the base material or powder requiring regeneration repair, the tensile strength of the base material after heat treatment decreases by 5.5% or less compared to the tensile strength of the base material immediately before the heat treatment step, or the tensile strength increases. In other words, the regeneration repair method of the present invention can secure the effect of having a small rate of decrease in tensile strength or, on the contrary, an increase in tensile strength even after heat treatment.

[0101] In addition, the yield strength that can be secured after heat treatment of the present invention can satisfy the following Equation 4.

[0102] [Equation 4]

[0103] {(CT - DT) / CT} × 100

[0104] CT is the yield strength of the base material that has been regenerated and repaired after heat treatment, and DT is the yield strength of the base material before heat treatment.

[0105] The lower limit of Equation 4 may be approximately 0%, 0.5%, or 0.8%, and the upper limit may be approximately 100%, 80%, 60%, 40%, 30%, 20%, 10%, or 5%, although it is not specifically limited. The value of Equation 4 may be in the range above or above the aforementioned lower limit.

[0106] That is, Equation 4 represents the rate of change of yield strength, and the meaning that the value of Equation 4 is within the range described above is that, after the step of melting the base material or powder requiring regeneration repair, the yield strength of the base material after heat treatment increases compared to the base material immediately before the heat treatment step. In other words, the regeneration repair powder of the present invention can secure the effect of increasing yield strength even after heat treatment.

[0107] (Example)

[0108] The present application will be explained in more detail below through experimental examples according to the present application, but the scope of the present application is not limited by the embodiments presented below.

[0109] [measurement method]

[0110] 1. Tensile strength

[0111] The uniaxial tensile test was performed using a universal testing machine (UT-100E, MTDI, Korea) at 1×10 -3 The test was conducted at room temperature (25℃) with a test rate of 0.5 / s. The data obtained after the test were plotted as a stress-strain curve, and the tensile strength was measured by analyzing the data at the point where the maximum load is applied in the plastic deformation region after the yield strength.

[0112] 2. Yield strength

[0113] The yield strength was measured by plotting the tensile strength results on a stress-strain curve. Yield strength is measured at the point where the material moves beyond the elastic region and plastic deformation occurs. However, since it is difficult to accurately identify the point where deformation occurs, the yield strength is defined as the point where the slope of the elastic region of the stress-strain curve is offset by 0.2% and the point of intersection with the stress-strain curve. The yield strength was measured using the above method.

[0114] 3. Elongation

[0115] The tensile strength results were plotted as a stress-strain curve to measure elongation. In the stress-strain curve, elongation is measured as the increase in gauge length due to the applied load; the value obtained by subtracting the strain in the elastic region from the fracture point was defined as elongation.

[0116] [Powder Composition]

[0117] Tables 1 and 2 below show the composition of the regenerative repair powders of the examples and comparative examples. In Tables 1 and 2, the unit of each composition content is weight%.

[0118] Cr Co Ti Al C B W Nb Ta Zr A 22.72 19.13 3.49 1.74 0.065 0.0044 2.1 0.84 1.29 0.0089 B 21.06 0.71 0.16 0.14 0.05 0.0027 - 4.06 - -

[0119] Fe Si S P Mn Mo Cu O N Ni A 0.12 0.027 0.003 0.00015 - - - 0.0155 0.0061 Remaining B 4.06 0.06 0.003 0.005 0.005 9.47 0.0091 0.0071 0.0051 Remaining

[0120] Specimen preparation using 100% powder and measurement of mechanical properties before heat treatment (Example 1)

[0121] A specimen was prepared using powder A. The specimen was prepared as a plate-shaped specimen based on ASTM E8M standards as shown in Fig. 2.

[0122] The specimen was fabricated by melting the powders of the examples and comparative examples with a high-temperature laser and then adding them in a 3D printing manner as shown in Fig. 1 using DED.

[0123] At this time, the coaxial gas flow rate was set to 7 l / min, the powder gas flow rate to 2.5 l / min, and the shielding gas flow rate to 5.0 l / min. The hatching space was set to 0.5 mm, the laser height to 0.25 mm, and the beam diameter to 800 µm. Additionally, the laser power was set to 450 W, the scan speed to 750 mm / s, and the power feed rate to 2 g / min to fabricate the specimen.

[0124] (Comparative Example 1)

[0125] B Except for the fact that the specimen was prepared as a powder, it was prepared in the same manner as Example 1-1.

[0126] For each example and comparative example, three specimens were prepared and the average values ​​of the measured yield strength, tensile strength, and elongation are summarized in Table 3 below.

[0127] Tensile strength (MPa) Yield strength (MPa) Elongation rate (%) Example 1 1090.21 837 32.68 Comparative Example 1 776.63 558.21 54.36

[0128] The powder of Comparative Example 1 is also commonly referred to as Alloy 625. The powder of Comparative Example 1 is a representative powder used in the technical field to which the present invention belongs, due to the fact that it has a low probability of high-temperature cracking or reheat cracking when welded by the GTAW welding method, and has excellent weldability due to its high strength. In other words, typically, when high-temperature strength is secured, mechanical properties such as high-temperature cracking may simultaneously be inferior. However, as can be seen in Table 3 above, it can be confirmed that the mechanical properties of Comparative Example 1 are significantly inferior to those of Example 1 even before heat treatment when repaired using the repair method of the present invention. Through this, it can be confirmed that the repair method of the present invention can secure excellent mechanical properties as well as weldability even before heat treatment.

[0129] Changes in mechanical properties after heat treatment

[0130] (Example 2-1)

[0131] For the specimen prepared in Example 1 above, heat treatment was performed at approximately 1180°C for about 120 minutes, and then the temperature was lowered to approximately 1080°C for about 120 minutes. After that, the temperature was lowered to approximately 850°C for about 24 hours.

[0132] (Example 2-2)

[0133] For the specimen prepared in Example 1 above, heat treatment was performed at approximately 1200°C for about 110 minutes, and then the temperature was lowered to approximately 980°C for about 120 minutes. After that, the temperature was lowered to approximately 860°C for about 24 hours.

[0134] (Comparative Example 2-1)

[0135] Heat treatment was performed in the same manner as in Example 2-1, but the heat treatment was performed on the specimen prepared in Comparative Example 1.

[0136] (Comparative Example 2-2)

[0137] For the specimen prepared in Example 1-1 above, heat treatment was performed at approximately 1400°C for about 130 minutes, and then the temperature was lowered to approximately 1000°C for about 120 minutes. After that, the temperature was lowered to approximately 800°C for about 24 hours.

[0138] (Comparative Example 2-3)

[0139] For the specimen prepared in Example 1-1 above, heat treatment was performed at approximately 1200°C for about 160 minutes, and then the temperature was lowered to approximately 800°C for about 24 hours.

[0141] Three specimens were prepared for each example and comparative example, and the average values ​​of yield strength and tensile strength measured after heat treatment are summarized in Table 4 below. In Table 4, the rate of change in tensile strength and yield strength is the rate of change relative to the base material immediately before the heat treatment step during the regeneration and repair stage.

[0142] Figure 3 is a stress-strain graph before and after heat treatment of Example 2-1.

[0143] Tensile strength (MPa) Change rate of tensile strength (%) Yield strength (MPa) Rate of change in yield strength (%) Example 2-1 1329.91 18 864.71 3.2 Example 2-2 1280.7 14.8 856 2.2 Comparative Example 2-1 733.84 -5.8 375 -48.9 Comparative Example 2-2 1080.22 -0.9 730 -14.7 Comparative Example 2-3 565.3 -92.85 430 -94.7

[0144] Comparative Example 2-1 was heat-treated in the same manner as Example 2-1. Referring to Table 4 above, it can be seen that Comparative Example 2-1 has a tensile strength of 733.84 MPa and a yield strength of 375 MPa, which is lower than the tensile strength of 776.63 MPa and yield strength of 558.21 MPa before heat treatment. In order to repair nickel-based superalloys, heat treatment must be performed after repairing with powder, so it is necessary to ensure mechanical properties after heat treatment.

[0145] Referring to Table 4 above, Example 2-1 secures higher strength compared to the tensile strength of 1090.21 MPa and yield strength of 837 MPa before heat treatment, and it can be confirmed that mechanical properties are secured even after heat treatment.

[0146] In addition, the above Examples 2-1 and 2-2 are examples in which heat treatment is performed within the scope of the step of heat treating the metal that has been restored according to the present invention. By appropriately lowering the temperature in three stages, the occurrence of cracks such as cracks due to rapid temperature changes is prevented, and strength can be secured even after heat treatment.

[0147] In contrast, Comparative Example 2-2 was performed in the first step at a very high temperature, and accordingly, the temperature difference with the second step was very large. In Comparative Example 2-2, it can be confirmed that mechanical properties were not secured after heat treatment because the regenerated repair powder was remelted and part of the base material was melted.

[0148] In addition, Comparative Example 2-3 is a comparative example in which heat treatment was not performed in three stages. In the case of Comparative Example 2-3, the effect of lowering the temperature stepwise was insufficient, resulting in insufficient time for the regenerated repair powder to blend with the base material, and thus it can be confirmed that mechanical properties were not secured after heat treatment.

[0149] Through this, it can be confirmed that, according to the regeneration and repair method of the present invention, excellent mechanical properties can be secured even after heat treatment.

[0151] Fracture location identification and strength measurement

[0152] (Reference Example 1 and Reference Example 2)

[0153] Reference Example 1 is a metal specimen made of 247LC metal, and Reference Example 2 is a metal specimen made of 792DS metal. The shape was prepared to be the same as that shown in FIG. 2.

[0154] Tables 5 and 6 below show the powder compositions of Reference Example 1 and Reference Example 2. In Tables 5 and 6, the unit of each composition content is weight%.

[0155] Cr Co Ti Al C B W Nb Ta Zr Reference Example 1 12.2 9 4.1 3.6 0.07 0.008 3.8 0.06 5 0.03 Reference Example 2 8.3 9.25 0.75 5.55 0.08 0.015 9.5 0.05 3.2 0.01

[0156] Fe Si Mn Mo Cu Hf Ni Reference Example 1 0.1 0.01 - 1.9 0.001 0.5 Remaining Reference Example 2 0.01 0.03 0.01 0.5 0.001 1.4 Remaining

[0157] (Example 3-1) The metal specimen of Reference Example 1 above was arbitrarily cut as shown in Fig. 4, and the cut portion was repaired using powder A. The conditions at this time were the same as those in Example 1-1. Afterwards, the repaired specimen was produced by heat treatment in the same manner as in Example 2-1.

[0158] (Comparative Example 3-1)

[0159] The metal specimen of Reference Example 1 above was arbitrarily cut as shown in Fig. 4, and the cut portion was repaired using D powder. The conditions at this time were the same as those in Example 1-1. Afterwards, the repaired specimen was produced by heat treatment in the same manner as in Example 2-1.

[0160] (Example 3-2)

[0161] The metal specimen of Reference Example 2 above was arbitrarily cut as shown in Fig. 4, and the cut portion was repaired using powder A. The conditions at this time were the same as those in Example 1-1. Afterwards, the repaired specimen was produced by heat treatment in the same manner as in Example 2-1.

[0162] (Comparative Example 3-2)

[0163] The metal specimen of Reference Example 2 above was arbitrarily cut as shown in Fig. 4, and the cut portion was repaired using D powder. The conditions at this time were the same as those in Example 1-1. Afterwards, the repaired specimen was produced by heat treatment in the same manner as in Example 2-1.

[0164] Tensile strength, yield strength, and elongation were measured for the regenerated metal specimens, and the locations where fracture occurred are summarized in Table 7 below. In Table 7, the rate of change in tensile strength and the rate of change in yield strength are the rates of change relative to the base material before regeneration.

[0165] Tensile strength (MPa) Change rate of tensile strength (%) Yield strength (MPa) Rate of change in yield strength (%) Elongation rate (%) Fracture location Reference Example 1 919.55 - 756.89 - 8.01 - Example 3-1 875.25 -5.1 769.09 1.5 6.15 247LC Comparative Example 3-1 763.93 -20 332.56 -127 34.68 Regeneration and repair department Reference Example 2 910.36 - 817.11 - 3.39 - Example 3-2 931.58 2.3 824.38 0.88 3.36 792DS Comparative Example 3-2 784.24 -16 339.05 -141 39.98 Regeneration and repair department

[0166] 247LC and 792DS, corresponding to Reference Example 1, are well-known metallic materials. In particular, 247LC is widely used as a superalloy. Referring to Table 5, in the case of Examples 3-1 and 3-2, which are manufactured using the regenerative repair method of the present invention for the regenerative repair of 247LC or 792DS materials, it can be confirmed that the deterioration of mechanical properties is less or superior strength is secured compared to 247LC or 792DS. Furthermore, since the fracture location is also 247LC or 792DS, it can be confirmed that the strength of the regeneratively repaired part is superior to that of the existing 247LC or 792DS materials.

[0167] In contrast, in the case of Comparative Examples 3-1 and 3-2, in which 247LC or 792DS materials were repaired, it can be seen that the mechanical properties were significantly degraded compared to 247LC or 792DS. Furthermore, since the fracture location was also in the repaired part, it can be seen that the strength of the repaired part is inferior to that of the original 247LC or 792DS material.

[0168] In particular, Comparative Example 3-1 has a tensile strength of 765.03 MPa and a yield strength of 330.57 MPa before heat treatment during the regeneration and repair stage, and Comparative Example 3-2 has a tensile strength of 787.82 MPa and a yield strength of 343.65 MPa before heat treatment during the regeneration and repair stage, so it can be confirmed that the tensile strength or yield strength of the base material before heat treatment is higher than the tensile strength or yield strength of the base material after heat treatment.

[0169] Through this, it can be confirmed that the regeneration repair method of the present invention can secure excellent mechanical properties after regeneration repair.

[0171] Identification of fracture location and strength measurement based on DED stacking

[0172] (Example 4-1)

[0173] A specimen was prepared in the shape shown in Fig. 2 using a metal having the same composition as powder A, and was cut arbitrarily as shown in Fig. 4, and the cut part was repaired using powder A.

[0174] The conditions at this time were set as follows: coaxial gas 7 l / min, powder gas 2.5 l / min, and shield gas 5.0 l / min; hatching space 0.5 mm; laser height 0.25 mm; and beam diameter 800 μm. In addition, the laser power was set to 350 W, the scan speed to 750 mm / s, and the power feed rate to 2 g / min.

[0175] (Example 4-2)

[0176] Repair was performed in the same manner as in Example 4-1, but the laser power was set to 450 W.

[0177] (Example 4-3)

[0178] Repair was performed in the same manner as in Example 4-1, but the laser power was set to 550 W.

[0179] (Example 4-4)

[0180] Repair was performed in the same manner as in Example 4-1, but with a laser power of 450 W and a scan speed of 700 mm / s.

[0181] (Examples 4-5)

[0182] Repair was performed in the same manner as in Example 4-1, but with a laser power of 450 W and a scan speed of 650 mm / s.

[0183] Three specimens of the regenerated and repaired specimens of Examples 4-1 to 4-5 were prepared for each specimen, and the yield strength, tensile strength, and elongation were measured and averaged, and summarized in Table 8 below.

[0184] FIG. 5 is a diagram showing the fracture locations of Examples 4-1 to 4-5. Specimens were fabricated under the same conditions, and measurements were taken after causing three fractures. In Examples 4-1 to 4-5, it can be confirmed that fracture occurs at the location of the metal base material between the repaired portion and the metal base material.

[0185] Tensile strength (MPa) Yield strength (MPa) Elongation rate (%) Fracture location Example 4-1 898.93 745.73 5.67 metal base material Example 4-2 838.90 690.90 6.80 metal base material Example 4-3 885.82 730.35 6.13 metal base material Examples 4-4 830.92 661.36 4.75 metal base material Examples 4-5 895.38 676.70 6.41 metal base material

[0186] Through this, it can be confirmed that in the case of the regeneration repair method of the present invention, even when a base material having the same components is repaired, excellent mechanical properties can be secured after regeneration repair.

[0187] As described above, preferred embodiments according to the present invention have been examined. It is obvious to those skilled in the art that, in addition to the embodiments described above, the present invention may be embodied in other specific forms without departing from the spirit or scope thereof. Therefore, the embodiments described above should be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the description above but may be modified within the scope of the appended claims and their equivalents.

Claims

Claim 1 A method for regeneration and repair comprising: a step of preparing a metal base material requiring regeneration and repair; a step of injecting regeneration and repair powder into a regeneration and repair portion; and a step of melting the regeneration and repair powder onto the base material through a laser; wherein the regeneration and repair powder comprises Cr 20 wt% or more and 23 wt% or less, Co 18 wt% or more and 20 wt% or less, Ti 3 wt% or more and 5 wt% or less, Al 1 wt% or more and 3 wt% or less, C 0.01 wt% or more and 0.2 wt% or less, B 0.001 wt% or more and 0.01 wt% or less, and the remainder being Ni and unavoidable impurities, satisfying the following formula 1: [Formula 1] {(A - B) / A} × 100 ≥ -5.5 % In Formula 1, A is the tensile strength of the regenerated base material after regeneration and repair, and B is the tensile strength of the base material requiring regeneration and repair. Claim 2 A method for repairing a regenerated material according to claim 1, further comprising a heat treatment step for performing heat treatment on a regenerated or repaired base material, wherein the heat treatment step comprises: a first step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 1000℃ or more and 1300℃ or less; a second step of performing heat treatment for a time of 90 minutes or more and 150 minutes or less in a temperature range of 900℃ or more and 1100℃ or less; and a third step of performing heat treatment for 20 hours or more and 25 hours in a temperature range of 700℃ or more and 900℃ or less. Claim 3 A repair and restoration method according to claim 1, wherein in the step of melting the powder with a laser, the laser power of the laser is within the range of 300W or more and 550W or less. Claim 4 A repair and restoration method according to claim 1, wherein in the step of melting the powder with a laser, the scan speed of the laser is within the range of 650 mm / s or more and 750 mm / s or less. Claim 5 delete Claim 6 A method for regeneration and repair according to claim 1, wherein the regeneration and repair powder further comprises one or more of W, Nb, Ta, or Zr in a range of 0.005% by weight or more and 3% by weight or less. Claim 7 A method for regeneration and repair according to claim 1, wherein the regeneration and repair powder further comprises Fe 0.5 wt% or less, Si or S 0.05 wt% or less, or P, N, Pb, Bi, Ag or O 0.001 wt% or less. Claim 8 A method for repairing a damaged portion according to paragraph 2, wherein the yield strength of the repaired portion after the heat treatment step is 820 MPa or higher. Claim 9 A repair method according to paragraph 2, wherein the tensile strength of the repaired portion after the heat treatment step is 1100 MPa or more.

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