Method for testing recrystallization depth-width relation of single crystal casting

Abstract

The invention belongs to the technical field of single crystal integrity defect detection of single crystal castings, and particularly relates to a method for testing a depth-width relation of recrystallization of a single crystal casting. According to typical morphology characteristics of recrystallization, a test method of test block preparation-preloading-solution treatment-metallographic analysis is designed, the recrystallization width-depth relation can be visually obtained, and the depth-width relation of recrystallization of a specific single crystal alloy casting is obtained through relation fitting of multi-load data. The method can be used for nondestructive measurement of the recrystallization depth.

Description

Technical Field

[0001] The invention belongs to the technical field of single crystal integrity defect detection of single crystal castings, and in particular relates to a method for testing the depth-width relationship of recrystallization of single crystal castings. Background Art

[0002] As a material with a temperature of more than 1000°C, single crystal high-temperature alloy castings have the ability to withstand high-temperature loads, especially their strong resistance to high-temperature creep, and are widely used in aerospace, aviation and energy fields. Recrystallization defects are typical grain size defects in single crystal alloy castings. As a source of fatigue crack expansion, their existence will greatly reduce the service life of castings. Therefore, various acceptance standards have high requirements for recrystallization in single crystal castings. However, different processes and structures will inevitably have recrystallization defects, so the regulation of their size is extremely important. Among them, the depth dimension, as a dimension that cannot be measured non-destructively at present, has the greatest impact on casting performance. The non-destructive measurement of recrystallization defects in specific single crystal alloys can be used as a reference for grinding and removing recrystallization defects in single crystal high-temperature alloys and as a basis for standard formulation. Therefore, a method for non-destructively measuring the depth of recrystallization is urgently needed. Summary of the invention

[0003] In view of the problems in the prior art, the present invention provides a method for testing the depth-width relationship of recrystallization of single crystal castings. According to the typical morphological characteristics of recrystallization, an experimental method of test block preparation-preloading-solid solution treatment-metallographic analysis is designed, which can intuitively obtain the relationship between the width and depth of recrystallization. The depth-width relationship of recrystallization of a specific single crystal alloy casting is obtained by fitting the relationship of multiple load data, which can be used for non-destructive measurement of the recrystallization depth.

[0004] The technical solution of the present invention is: A method for testing the depth-width relationship of recrystallization of a single crystal casting comprises the following steps: Step (1) preparing a plurality of single crystal cast test blocks of the same size and shape; Step (2) using a Brinell hardness tester to perform an indentation treatment on each single crystal cast test block with an indentation load, wherein the difference between two adjacent indentation loads is not less than 100 kg; the indentation loads are not less than 6, and at least 4 single crystal cast test blocks are indented under each indentation load; Step (3) subjecting the single crystal cast test block after the indentation treatment to a vacuum solution heat treatment specifically for the alloy; Step (4) Use wire cutting to cut the single crystal cast test block along the indentation diameter, observe the recrystallization morphology of the single crystal cast test block in the longitudinal section, and measure the maximum recrystallization depth D of each single crystal cast test block under each load along the bottom of the indentation. And the maximum width data W, and fitting to get the relationship between the depth and width of recrystallization formula.

[0005] Furthermore, in the above-mentioned method for testing the depth-width relationship of recrystallization of a single crystal casting, the single crystal cast test block in step (1) is obtained by wire cutting or directly casting a cast casting of other shapes and sizes, and the final shape of the single crystal cast test block is a rectangular parallelepiped, and the length, width and height dimensions are not less than 30 mm, 30 mm and 15 mm respectively.

[0006] Furthermore, in the above-mentioned method for testing the depth-width relationship of recrystallization of a single crystal casting, the diameter of the indenter of the Brinell hardness tester used in step (2) is 5 mm, the holding time of the indentation treatment is 11-13 s, and the indentation is located in the middle of the surface formed by the length and width of the single crystal cast specimen.

[0007] Furthermore, in the above-mentioned method for testing the depth-width relationship of recrystallization of a single crystal casting, the indentation load in step (2) needs to include 0 kg.

[0008] Furthermore, in the above-mentioned method for testing the depth-width relationship of recrystallization of single crystal castings, the maximum depth D is the average value of the maximum depths of recrystallization of multiple single crystal cast test blocks under each indentation load; the maximum width data W is the average value of the recrystallization widths of multiple single crystal cast test blocks under each indentation load, and the coordinate points (W, D) under different indentation loads are obtained, and the linear relationship formula is obtained based on each coordinate point.

[0009] Advantages and beneficial effects of the present invention: 1. The present invention can efficiently measure the recrystallization depth, determine the recrystallization size, and improve the grain size polishing pass rate of single crystal castings; 2. The method of the present invention can be used as a reference for polishing and removing recrystallization defects of single crystal high-temperature alloys and as a basis for formulating standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The size and position of the indenter of the single crystal as-cast test block are shown in the figure; Figure 2 Schematic diagram of sampling for recrystallization width and depth measurement. DETAILED DESCRIPTION

[0011] The specific implementation modes of the present invention are further described in detail below in conjunction with the drawings and examples of the specification. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention. Example 1

[0012] This embodiment is a method for testing the depth-width relationship of recrystallization of a single crystal casting. A second-generation single crystal high-temperature alloy is used to cast a 30mm*30mm*150mm square single crystal test bar, and a wire cutting device is used to cut 24 square single crystal cast test blocks with a size of 30mm*30mm*15mm. Figure 1As shown, the Brinell hardness tester was used to perform indentation treatment on each test block at the center of the surface formed by the length and width of the test block with indentation loads of 0kg, 250kg, 500kg, 750kg, 1000kg, and 1500kg, respectively. Four test blocks were indented under each indentation load, the indenter diameter was 5mm, and the holding time was 13s. After vacuum solution heat treatment at 1250℃*4h and air cooling, each single crystal cast test block was cut along the indentation diameter by wire cutting, as shown in FIG. Figure 2 As shown in the figure, it is a schematic diagram of the sampling for recrystallization width and depth measurement. The depth-width data of recrystallization under each load is measured, and the average maximum depth D and maximum width data W under each load are calculated, and 6 coordinate points (0, 0), (870, 580), (1200, 760), (1700, 975), (2600, 1256), and (3300, 1595) are obtained. The final linear formula obtained by fitting is D=0.51W. Example 2

[0013] The present embodiment provides a method for testing the depth-width relationship of recrystallization of a single crystal casting. A first-generation single crystal high-temperature alloy is used to cast a 30mm*30mm*150mm square single crystal test bar, and a wire cutting device is used to cut 32 square single crystal cast test blocks with a size of 30mm*30mm*15mm. A Brinell hardness tester is used to perform indentation treatment on each test block at an indentation load of 0kg, 150kg, 300kg, 550kg, 800kg, 1150kg, 1500kg, and 1750kg in the middle of the surface formed by the length and width of the test block. Four test blocks are indented under each indentation load, the indenter diameter is 5mm, and the load holding time is 13s. After vacuum solution heat treatment at 1250℃*4h and air cooling, each single crystal cast specimen was cut along the indentation diameter by wire cutting. The depth-width data of recrystallization under each load was measured, and the average maximum depth D and maximum width W under each load were calculated. Seven coordinate points were obtained: (0, 0), (350, 178), (700, 360), (1320, 600), (2030, 940), (2970, 1355), (3500, 1760), and (4300, 2040). The final linear formula obtained by fitting was D=0.48W.

Claims

1. A method for testing the depth-width relationship of recrystallization of a single crystal casting, characterized in that: The following steps are involved: Step (1) preparing a plurality of single crystal cast test blocks of the same size and shape; Step (2) using a Brinell hardness tester to perform an indentation treatment on each single crystal cast test block with an indentation load, wherein the difference between two adjacent indentation loads is not less than 100 kg; the indentation loads are not less than 6, and at least 4 single crystal cast test blocks are indented under each indentation load; Step (3) subjecting the single crystal cast test block after the indentation treatment to a vacuum solution heat treatment specifically for the alloy; Step (4) Use wire cutting to cut the single crystal cast test block along the indentation diameter, observe the recrystallization morphology of the single crystal cast test block in the longitudinal section, and measure the maximum recrystallization depth D of each single crystal cast test block under each load along the bottom of the indentation. And the maximum width data W, and fitting to get the relationship between the depth and width of recrystallization formula.

2. A method for testing the depth-width relationship of recrystallization of a single crystal casting according to claim 1, characterized in that: The single crystal as-cast test block in step (1) is obtained by wire cutting or directly casting from as-cast castings of other shapes and sizes. The final shape of the single crystal as-cast test block is a rectangular parallelepiped, and the length, width and height are not less than 30 mm, 30 mm and 15 mm respectively.

3. A method for testing the depth-width relationship of recrystallization of a single crystal casting according to claim 1, characterized in that: The diameter of the indenter of the Brinell hardness tester used in step (2) is 5 mm, the holding time of the indentation treatment is 11-13 s, and the indentation is located in the middle of the surface formed by the length and width of the single crystal cast test block.

4. A method for testing the depth-width relationship of recrystallization of a single crystal casting according to claim 1, characterized in that: Step (2) The indentation load needs to include 0 kg.

5. A method for testing the depth-width relationship of recrystallization of a single crystal casting according to claim 4, characterized in that: The maximum depth D is the average value of the maximum recrystallization depths of multiple single crystal cast specimens under each indentation load; the maximum width data W is the average value of the recrystallization widths of multiple single crystal cast specimens under each indentation load, and the coordinate points (W, D) under different indentation loads are obtained, and the linear relationship formula is obtained based on each coordinate point.

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