A method for eliminating microcracks inside electron beam welds of cobalt-based high-temperature alloys

Abstract

The present invention provides a method for eliminating microcracks inside electron beam welds of cobalt-based high-temperature alloys. The method provided by the present invention comprises the following steps: a) hot isostatic pressing the welded part; wherein the welded part is a GH5188 alloy welded part; the conditions of the hot isostatic pressing treatment are: temperature 1150-1180°C, pressure 150-180MPa, and heat preservation and pressure holding time 2-5h; b) solution treatment of the welded part obtained in step a). The method provided by the present invention can effectively eliminate microcrack defects inside electron beam welds of cobalt-based high-temperature alloys, and at the same time can improve the mechanical properties of the welded joint without deteriorating the mechanical properties of the matrix.

Description

Technical Field

[0001] The invention relates to the field of welding, and in particular to a method for eliminating micro cracks inside a cobalt-based high-temperature alloy electron beam weld. Background Art

[0002] Cobalt-based high-temperature alloys have excellent high-temperature thermal strength and high-temperature oxidation resistance, and are widely used in the manufacture of parts such as aircraft engine combustion chambers, guide blades, and aerospace engine thrust chambers.

[0003] Fusion welding (including argon arc welding, laser welding, and electron beam welding) is an indispensable process for manufacturing parts of this type of material. However, since a large amount of carbides often precipitate at the grain boundaries of the alloy, under the combined action of stress and thermal cycles during welding, the densely distributed carbides at the grain boundaries of the matrix dissolve and form liquid cracks, and extend into the weld. As a result, a large number of microcrack defects often form in the heat-affected zone and near the fusion line of the alloy in engineering applications, and ultimately lead to problems such as out-of-tolerance and scrap. Since the microcracks are difficult to detect using traditional X-ray detection and are numerous, it is difficult to achieve argon arc welding or laser cladding repair welding after eliminating the defects using traditional mechanical methods. Therefore, how to eliminate the microcrack defects to obtain welded parts with internal quality and mechanical properties that meet the requirements has important engineering applications and economic value. Summary of the invention

[0004] In view of this, the present invention provides a method for eliminating microcracks inside electron beam welds of cobalt-based high-temperature alloys. The method provided by the present invention can effectively eliminate microcrack defects inside electron beam welds of cobalt-based high-temperature alloys, and at the same time can improve the mechanical properties of the welded joint without deteriorating the mechanical properties of the matrix.

[0005] The present invention provides a method for eliminating microcracks inside a cobalt-based high-temperature alloy electron beam weld, comprising the following steps:

[0006] a) Perform hot isostatic pressing on welded parts;

[0007] in,

[0008] The welded parts are GH5188 alloy welded parts;

[0009] The conditions of the hot isostatic pressing treatment are: temperature 1150-1180°C, pressure 150-180MPa, and heat and pressure holding time 2-5h;

[0010] b) performing a solution treatment on the weldment obtained in step a).

[0011] Preferably, in step b), the conditions of the solution treatment are: temperature 1180±10° C., and holding time 1 to 3 hours.

[0012] Preferably, in step b), rapid cooling is performed after the solution treatment.

[0013] Preferably, the target temperature of the rapid cooling is cooling to below 150°C.

[0014] Preferably, in step a), the welded part is a welded part obtained by electron beam welding process.

[0015] Preferably, in step b), the heating rate of the solution treatment is 5 to 20° C. / min.

[0016] The method provided by the present invention first performs hot isostatic pressing treatment on the GH5188 alloy weldment and controls certain treatment conditions, and then performs a certain solution treatment. Through the above treatment, the microcrack defects inside the electron beam weld of the cobalt-based high-temperature alloy can be effectively eliminated, and the internal microcracks can be completely eliminated. Compared with the traditional method of eliminating defects and repairing welding, it has the advantages of simple and reliable process, small deformation, and low cost. The method of the present invention solves the problems of out-of-tolerance and scrap caused by welding defects in the process of parts manufacturing, greatly reduces the cost of parts manufacturing, and has important economic value. Moreover, after eliminating cracks, the method of the present invention can also improve the mechanical properties of the welded joint without deteriorating the matrix properties.

[0017] The test results show that the microcracks inside the weld are effectively eliminated by treating the welded parts according to the method of the present invention. At the same time, the room temperature tensile strength of the welded joint reaches more than 910MPa, the yield strength Rp0.2 reaches more than 399MPa, and the elongation at break reaches more than 44%, showing excellent tensile properties and plasticity. Moreover, the room temperature tensile strength of the matrix reaches more than 900MPa, the yield strength Rp0.2 reaches more than 390MPa, and the elongation at break reaches more than 53%. The room temperature tensile strength and plasticity meet the technical index requirements of the matrix material performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 This is the appearance diagram of the welded part obtained in Preparation Example 1;

[0020] Figure 2 This is a low-magnification morphology image of the weld cross section of the welded part obtained in Preparation Example 1;

[0021] Figure 3This is the weld microcrack morphology of the welded part obtained in Preparation Example 1;

[0022] Figure 4 This is a low-magnification morphology image of the weld cross section of the product obtained in Example 1;

[0023] Figure 5 This is the microstructure morphology of the weld of the product obtained in Example 1 after microcracks are eliminated. DETAILED DESCRIPTION

[0024] The present invention provides a method for eliminating microcracks inside a cobalt-based high-temperature alloy electron beam weld, comprising the following steps:

[0025] a) Perform hot isostatic pressing on welded parts;

[0026] in,

[0027] The welded parts are GH5188 alloy welded parts;

[0028] The conditions of the hot isostatic pressing treatment are: temperature 1150-1180°C, pressure 150-180MPa, and heat and pressure holding time 2-5h;

[0029] b) performing a solution treatment on the weldment obtained in step a).

[0030] The method provided by the present invention first performs hot isostatic pressing treatment on the GH5188 alloy weldment and controls certain treatment conditions, and then performs a certain solution treatment. Through the above treatment, the microcrack defects inside the electron beam weld of the cobalt-based high-temperature alloy can be effectively eliminated, and the internal microcracks can be completely eliminated. Compared with the traditional method of eliminating defects and repairing welding, it has the advantages of simple and reliable process, small deformation, and low cost. The method of the present invention solves the problems of out-of-tolerance and scrap caused by welding defects in the process of parts manufacturing, greatly reduces the cost of parts manufacturing, and has important economic value. Moreover, after eliminating cracks, the method of the present invention can also improve the mechanical properties of the welded joint without deteriorating the matrix properties.

[0031] Regarding step a) :

[0032] a) Perform hot isostatic pressing on the welded parts.

[0033] In the present invention, the welded part refers to a welded product obtained by welding two or more parts substrates through a welding process; wherein, the joint of two or more parts welded together is a welded joint, including a weld, a fusion zone, and a heat-affected zone, etc. In the present invention, the welded part is a GH5188 alloy welded part; specifically, the GH5188 alloy bar can be first processed into parts, and then welded to obtain a welded part. The present invention has no special restrictions on the source of the GH5188 alloy bar, which can be a commercial product on the market or prepared according to conventional preparation methods well known to those skilled in the art.

[0034] In the present invention, the welded part is preferably a welded part obtained by electron beam welding. The conditions of the electron beam welding process are preferably: acceleration voltage 60-150 kV, beam current 20-70 mA, welding speed 8-20 mm / s, scanning amplitude 0.5-2.0 mm. Among them, the acceleration voltage can be specifically 60 kV, 70 kV, 80 kV, 90 kV, 100 kV, 110 kV, 120 kV, 130 kV, 140 kV, 150 kV. The beam current can be specifically 20 mA, 25 mA, 30 mA, 35 mA, 40 mA, 45 mA, 50 mA, 55 mA, 60 mA, 65 mA, 70 mA. The welding speed may be 8 mm / s, 9 mm / s, 10 mm / s, 11 mm / s, 12 mm / s, 13 mm / s, 14 mm / s, 15 mm / s, 16 mm / s, 17 mm / s, 18 mm / s, 19 mm / s, 20 mm / s. The scanning amplitude may be 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm.

[0035] In the present invention, the welded parts are first subjected to hot isostatic pressing treatment, wherein the conditions for the hot isostatic pressing treatment are: temperature 1150-1180° C., pressure 150-180 MPa, and heat and pressure holding time 2-5 hours. The insulation temperature may specifically be 1150°C, 1151°C, 1152°C, 1153°C, 1154°C, 1155°C, 1156°C, 1157°C, 1158°C, 1159°C, 1160°C, 1161°C, 1162°C, 1163°C, 1164°C, 1165°C, 1166°C, 1167°C, 1168°C, 1169°C, 1170°C, 1171°C, 1172°C, 1173°C, 1174°C, 1175°C, 1176°C, 1177°C, 1178°C, 1179°C and 1180°C. The holding pressure may specifically be 150MPa, 151MPa, 152MPa, 153MPa, 154MPa, 155MPa, 156MPa, 157MPa, 158MPa, 159MPa, 160MPa, 161MPa, 162MPa, 163MPa, 164MPa, 165MPa, 166MPa, 167MPa, 168MPa, 169MPa, 170MPa, 171MPa, 172MPa, 173MPa, 174MPa, 175MPa, 176MPa, 177MPa, 178MPa, 179MPa, 180MPa. The heat preservation and pressure holding time may specifically be 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.5h. In the present invention, after hot isostatic pressing, cooling is performed, preferably cooling in the furnace to below 300° C., and then taking out of the furnace.

[0036] Regarding step b) :

[0037] b) performing a solid solution treatment on the weldment obtained in step a).

[0038] In the present invention, the conditions of the solution treatment are preferably: temperature 1180±10°C, holding time 1 to 3h. Wherein, the holding temperature can be specifically 1170°C, 1171°C, 1172°C, 1173°C, 1174°C, 1175°C, 1176°C, 1177°C, 1178°C, 1179°C, 1180°C, 1181°C, 1182°C, 1183°C, 1184°C, 1185°C, 1186°C, 1187°C, 1188°C, 1189°C, 1190°C. The holding time can be specifically 1.0h, 1.5h, 2.0h, 2.5h, 3.0h. In the present invention, the heating rate of the solution treatment is preferably 5 to 20°C / min, specifically 5°C / min, 10°C / min, 15°C / min, 20°C / min.

[0039] In the present invention, the solution treatment is preferably vacuum solution treatment, that is, the solution treatment is performed under vacuum conditions. In the present invention, the vacuum degree of the vacuum solution treatment is preferably 0.01-0.001 Pa, specifically 0.001 Pa, 0.003 Pa, 0.005 Pa, 0.007 Pa, 0.008 Pa, 0.01 Pa; the vacuum degree = atmospheric pressure - absolute pressure. In the present invention, the vacuum solution treatment can be performed in a vacuum gas quenching furnace.

[0040] In the present invention, after the above-mentioned solution treatment, rapid cooling is preferably performed. In the present invention, the method of rapid cooling is preferably to fill the solution treatment furnace with argon for rapid cooling. In the present invention, the target temperature of the rapid cooling is preferably cooled to below 150°C before being taken out of the furnace. After the above treatment, the specimen can be machined to the required part size.

[0041] The method provided by the present invention first performs hot isostatic pressing treatment on the GH5188 alloy weldment and controls certain treatment conditions, and then performs a certain solution treatment. Through the above treatment, the microcrack defects inside the electron beam weld of the cobalt-based high-temperature alloy can be effectively eliminated, and the internal microcracks can be completely eliminated. Compared with the traditional method of eliminating defects and repairing welding, it has the advantages of simple and reliable process, small deformation, and low cost. The method of the present invention solves the problems of out-of-tolerance and scrap caused by welding defects in the process of parts manufacturing, greatly reduces the cost of parts manufacturing, and has important economic value. Moreover, after eliminating cracks, the method of the present invention can also improve the mechanical properties of the welded joint without deteriorating the matrix properties.

[0042] The test results show that the microcracks inside the weld are effectively eliminated by treating the welded parts according to the method of the present invention. At the same time, the room temperature tensile strength of the welded joint reaches more than 910MPa, the yield strength Rp0.2 reaches more than 399MPa, and the elongation at break reaches more than 44%, showing excellent tensile properties and plasticity. Moreover, the room temperature tensile strength of the matrix reaches more than 900MPa, the yield strength Rp0.2 reaches more than 390MPa, and the elongation at break reaches more than 53%. The room temperature tensile strength and plasticity meet the technical index requirements of the matrix material performance.

[0043] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0044] Preparatory Example 1

[0045] The GH5188 alloy rod was processed into two test rings of the same size (80 mm in diameter and 8 mm in wall thickness). Then, the two test rings were welded together by electron beam welding. The process parameters of electron beam welding were: acceleration voltage 150 kV, beam current 35 mA, welding speed 10 mm / s, scanning amplitude 0.6 mm, and finally a welded part was obtained.

[0046] The appearance of the welded part is as follows: Figure 1 shown.

[0047] The welded parts were dissected and then subjected to metallographic examination. Figure 2-3 As shown, it can be seen that there are a large number of microcrack defects near the weld fusion line.

[0048] Example 1

[0049] 1. Treatment method

[0050] a1) Prepare a weldment according to Preparatory Example 1.

[0051] a2) The welded parts are subjected to hot isostatic pressing treatment with the following process parameters: temperature 1165°C, pressure 165MPa, heat and pressure maintenance for 3h, and the furnace is cooled to below 300°C before being taken out of the furnace.

[0052] b) The test piece is placed in a vacuum gas quenching furnace for vacuum solution treatment. The process parameters are: vacuum degree 0.001Pa, heating to 1180°C at 5°C / min and keeping warm for 1h, then filling with argon and quickly cooling to below 150°C before taking out of the furnace to obtain the product.

[0053] 2. Testing

[0054] (1) X-ray inspection of the internal quality of the weld of the obtained product meets the requirements of GJB 1718A-2005 (Grade I).

[0055] (2) Fluorescence testing of the weld surface of the obtained product was carried out and it met the Grade A requirements in GJB 5854-2006.

[0056] (3) Metallographic examination of the obtained product, the results are as follows Figure 4-5 As shown. It can be seen that there are no microcrack defects in the weld and the heat-affected zone. By comparing the effects of Preparatory Example 1 and Example 1, it can be seen that the microcrack defects in the weld of the cobalt-based high-temperature alloy are effectively eliminated by treating the weld joint according to the method of the present invention.

[0057] Example 2

[0058] 1. Treatment method

[0059] a1) Prepare a weldment according to Preparatory Example 1.

[0060] a2) The welded parts are subjected to hot isostatic pressing treatment with the following process parameters: temperature 1150°C, pressure 150MPa, heat and pressure maintenance for 5 hours, and the furnace is cooled to below 300°C before being taken out of the furnace.

[0061] b) The test piece is placed in a vacuum gas quenching furnace for vacuum solution treatment. The process parameters are: vacuum degree 0.01Pa, heating to 1190°C at 15°C / min and keeping warm for 3h, then filling with argon and quickly cooling to below 150°C before taking out of the furnace to obtain the product.

[0062] 2. Testing

[0063] (1) X-ray inspection of the internal quality of the weld of the obtained product meets the requirements of GJB 1718A-2005 (Grade I).

[0064] (2) Fluorescence testing of the weld surface of the obtained product was carried out and it met the Grade A requirements in GJB 5854-2006.

[0065] (3) The metallographic examination of the obtained product showed that there were no microcrack defects in the weld and heat-affected zone.

[0066] Example 3

[0067] 1. Treatment method

[0068] a1) Prepare a weldment according to Preparatory Example 1.

[0069] a2) The welded parts are subjected to hot isostatic pressing treatment with the following process parameters: temperature 1180°C, pressure 180MPa, heat and pressure maintenance for 2h, and the furnace is cooled to below 300°C before being taken out of the furnace.

[0070] b) The test piece is placed in a vacuum gas quenching furnace for vacuum solution treatment. The process parameters are: vacuum degree 0.005Pa, heating to 1170°C at 10°C / min and keeping warm for 2h, then filling with argon and quickly cooling to below 150°C before taking out of the furnace to obtain the product.

[0071] 2. Testing

[0072] (1) X-ray inspection of the internal quality of the weld of the obtained product meets the requirements of GJB 1718A-2005 (Grade I).

[0073] (2) Fluorescence testing of the weld surface of the obtained product was carried out and it met the Grade A requirements in GJB 5854-2006.

[0074] (3) The metallographic examination of the obtained product showed that there were no microcrack defects in the weld and heat-affected zone.

[0075] Comparative Example 1

[0076] The method is implemented in accordance with Example 1, except that the hot isostatic pressing treatment in step a2) is not performed on the welded part, and only the vacuum solution treatment in step b) is performed.

[0077] Comparative Example 2

[0078] The method is implemented in accordance with Example 1, except that in step a2), the temperature of the hot isostatic pressing treatment is increased to 1230° C. and the pressure is increased to 200 MPa.

[0079] Comparative Example 3

[0080] The method is implemented in accordance with Example 1, except that in step a2), the temperature of the hot isostatic pressing treatment is reduced to 1100° C. and the pressure is reduced to 100 MPa.

[0081] Comparative Example 4

[0082] The process is carried out in accordance with Example 1, except that in step b), the temperature of the vacuum solution treatment is increased to 1220°C.

[0083] Comparative Example 5

[0084] The process is carried out in accordance with Example 1, except that in step b), the temperature of the vacuum solution treatment is reduced to 1130°C.

[0085] Example 4: Product Testing

[0086] 1. Welding joint performance test

[0087] The room temperature tensile properties of the welded joints were tested for the original welded parts obtained in Preparatory Example 1, the products obtained in Examples 1-3, and the products obtained in Comparative Examples 1-5, respectively. The results are shown in Table 1.

[0088] Table 1: Room temperature tensile properties of welded joints

[0089]

[0090] Note: In Table 1, yield strength Rp0.2 refers to the elongation strength when the specified non-proportional elongation is 0.2%. Elongation after fracture A refers to _ The ratio of the residual elongation of the gauge length after fracture to the original gauge length. The section shrinkage Z refers to the ratio of the maximum reduction in the cross-sectional area of ​​the specimen after fracture to the original cross-sectional area.

[0091] It can be seen from the test results in Table 1 that the room temperature tensile strength of the welded joints of the products obtained in Examples 1-3 of the present invention reaches more than 910MPa, the yield strength Rp0.2 reaches more than 399MPa, and the elongation after fracture reaches more than 44, showing excellent mechanical properties. Compared with Preparatory Example 1, the room temperature tensile properties of Examples 1-3 are significantly improved, proving that the room temperature tensile properties of the welded joints can be effectively improved by treating the welded parts according to the method of the present invention while eliminating the microcracks inside the weld. Compared with Example 1, the room temperature tensile mechanical properties of Comparative Examples 2-3 are significantly reduced, proving that if the temperature of the hot isostatic pressing treatment is too high or too low, and the pressure is too high or too low, it is not conducive to the mechanical properties of the product. The present invention controls under certain hot isostatic pressing conditions to effectively improve the room temperature tensile mechanical properties of the welded joint. Compared with Example 1, the room temperature tensile mechanical properties of Comparative Examples 4-5 are significantly reduced, proving that if the temperature of the solution treatment is too high or too low, it is not conducive to the mechanical properties of the product. The present invention controls under certain solution treatment conditions to effectively improve the room temperature tensile mechanical properties of the welded joint.

[0092] 2. Matrix performance test

[0093] The room temperature tensile property test was performed on the test ring matrix part of the weldment, and the average value of the test results of the two test ring matrices in each weldment was taken as the test result of the sample. Both Example 1 and Comparative Example 1 were tested, and the results are shown in Table 2.

[0094] Table 2: Room temperature tensile properties of the matrix

[0095]

[0096] It can be seen from the test results in Table 2 that after the weldment is processed according to the method of the present invention, the room temperature tensile strength and plasticity of the matrix meet the technical index requirements of the matrix material performance, proving that the method of the present invention does not reduce the mechanical properties of the matrix while eliminating the microcracks inside the weld.

[0097] It can be seen from all the above test results that treating the welded parts according to the method of the present invention can effectively eliminate the microcracks inside the weld, and at the same time, can also improve the room temperature tensile properties and plasticity of the welded joint without reducing the mechanical properties of the matrix.

[0098] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for eliminating microcracks inside electron beam welds of cobalt-based high-temperature alloys, characterized in that: The following steps are involved: a) Perform hot isostatic pressing on welded parts; in, The welded parts are GH5188 alloy welded parts; The conditions of the hot isostatic pressing treatment are: temperature 1150-1180°C, pressure 150-180MPa, and heat and pressure holding time 2-5h; b) performing a solution treatment on the weldment obtained in step a); The conditions of the solution treatment are: temperature 1180±10°C, holding time 1 to 3 hours; The heating rate of the solution treatment is 5 to 20°C / min.

2. The method according to claim 1, characterized in that In step b), after the solution treatment, rapid cooling is performed.

3. The method according to claim 2, characterized in that The target temperature of the rapid cooling is cooling to below 150°C.

4. The method according to claim 1, characterized in that: In step a), the welded part is a welded part obtained by electron beam welding.

Images