Method for measuring wetting angle between alloy melt and ceramic mold shell

Abstract

The invention discloses a method for measuring a wetting angle between an alloy melt and a ceramic mold shell, and the method comprises the following steps: 1, enabling an alloy ingot to be in contact with the ceramic mold shell, and carrying out the high-temperature smelting, thereby obtaining a smelting sample composed of the alloy ingot and the ceramic mold shell; step 2, cutting the smelted sample obtained in the step 1 into a size matched with that of the ceramic wafer, so that the contact surface of the ceramic wafer and the smelted sample is kept horizontal; 3, keeping the contact surface of the smelting sample and the ceramic chip horizontal, aligning a horizontal line in the camera to the contact surface of the smelting sample and the ceramic chip, and taking a sample picture; rotating the sample according to a certain angle after shooting of one sample to obtain sample horizontal photos in different directions, and obtaining enough sample negative films; 4, performing primary processing on the obtained negative film, and performing fitting processing on the picture by using wetting angle processing software to obtain corresponding wetting angle data; and carrying out secondary processing on the data to obtain a final result.

Description

Technical Field

[0001] The invention belongs to the research field of nickel-based high-temperature alloy smelting and wetting phenomenon, and in particular relates to a method for measuring a wetting angle between an alloy melt and a ceramic mold shell. Background Art

[0002] It is well known that during the high-temperature alloy casting process, the interface reaction between the alloy and the ceramic shell and core materials will cause surface defects such as reaction layer or sand adhesion layer to form on the surface of the casting, reduce the surface quality of the casting, and affect the dimensional accuracy and subsequent processing of the casting. The wettability of alloy melt and ceramic material is closely related to the interface reaction. The interface reaction generally increases the wettability, making it easier for the alloy melt to penetrate into the pores of the ceramic surface layer and cause problems such as rough surface of the casting. The active elements in the alloy, the composition of the ceramic material, the alloy pouring temperature, etc. are important factors affecting the interface reaction. Therefore, it is of great theoretical and practical significance to carry out research on the wettability and interface reaction of high-temperature alloys and ceramic materials, and to explore the influence of active elements in the alloy and the composition of ceramic materials on the interface reaction of high-temperature alloys / ceramic materials.

[0003] The wetting angle of nickel-based superalloy is one of the important parameters for evaluating its wetting performance. The wetting performance of superalloy is closely related to the interface reaction and affects the surface sand adhesion phenomenon, which is one of the important factors that ultimately determine the quality of smelting superalloy. The principle of wetting angle to characterize wettability is based on the solid-liquid-gas three-phase equilibrium equation proposed by Thomas Young in 1804:

[0004] σ sv =σ sl +σ lv cosθ

[0005] where σ sv , σ sl and σ lv They represent the solid / gas interface energy, solid / liquid interface energy and liquid / gas interface energy respectively, and θ represents the wetting angle of the solid / liquid interface. The Thomas Young equation is derived based on the ideal surface (i.e., the substrate surface is smooth, homogeneous, and rigid) and the mechanical equilibrium of the solid-liquid-gas three-phase at the intersection. sv , σ sl and σ lv The sizes of the three factors together determine the size of the wetting angle θ. Generally speaking, the factors that affect the wettability of the alloy melt and the ceramic shell include: alloy composition, shell material type, surrounding atmosphere properties, oxidation degree of the alloy liquid, etc.

[0006] Based on Young's equation, there are many methods to measure the wetting angle and surface tension, such as the sessile drop method, vertical rod method, tilted plate method, capillary rise method, etc. Among these methods, the sessile drop method is the easiest to implement. The basic principle of the sessile drop method is to heat the alloy to be melted and the substrate to the experimental temperature together, and then measure the wetting parameters. The general measurement principle of the experimental sample obtained by the sessile drop method is: measure the bottom diameter d and height h of the alloy ball and perform geometric calculations, and obtain the value of the wetting angle through the formula θ=2acrtan(2h / d). The specific principle is as follows Figure 1 However, after the sessile drop method is completed, the morphology of the experimental sample is difficult to form as shown in most cases. Figure 1 The complete alloy sphere shown usually has certain irregularities, asymmetries, and morphological defects such as edges and corners.

[0007] The current solutions are as follows:

[0008] First, an experimental device with a camera is used to directly take real-time photos of the metal droplets and ceramic sheets during high-temperature melting to measure their wetting angles. However, this method takes a long time to experiment, with one experiment taking a whole day, and the equipment is very expensive.

[0009] Second, a method of using a vernier caliper to measure the bottom diameter d and height h of the alloy ball and perform geometric calculations, but this method limits the shape of the droplet, and due to the limitations of the sample morphology, the measurement accuracy has great limitations.

[0010] Third, grind off half of the metal ingot along the side section direction, then embed it, and measure its wetting angle through secondary electron photography under a scanning electron microscope. Although this method is scientific and reliable, it is still cumbersome to measure the wetting angle of a large number of samples. When a large number of experimental data are needed to carry out a more in-depth study of the wetting phenomenon, this method is difficult to meet the research needs. Summary of the invention

[0011] In order to solve the problems existing in the prior art, the present invention provides a method for measuring the wetting angle between an alloy melt and a ceramic mold shell, comprising the following steps:

[0012] Step 1: contacting the alloy ingot with the ceramic mold shell and performing high-temperature smelting to obtain a smelting sample consisting of the alloy ingot and the ceramic mold shell;

[0013] Step 2: Cut the smelted sample obtained in step 1 into a size suitable for the ceramic sheet, so that the contact surface between the ceramic sheet and the smelted sample remains horizontal;

[0014] Step 3: First keep the contact surface between the molten sample and the ceramic sheet horizontal, then align the horizontal line in the camera with the contact surface between the molten sample and the ceramic sheet and take a photo of the sample;

[0015] After each shot, rotate the sample at a certain angle to obtain horizontal photos of the sample in different directions and obtain a sufficient number of sample negatives;

[0016] Step 4: Perform preliminary processing on the obtained film, and then use the wetting angle processing software to fit the photo to obtain the corresponding wetting angle data; then perform secondary processing on these data to obtain the final result.

[0017] In a preferred embodiment of the present invention, the diameter of the alloy ingot ranges from 5 to 15 mm.

[0018] In a preferred embodiment of the present invention, the high temperature smelting is carried out in a sessile drop method apparatus using a crucible as a carrying container for the alloy ingot and the ceramic sheet. The preferred crucible material is alumina, magnesia, graphite, metal molybdenum or metal tungsten.

[0019] In a preferred embodiment of the present invention, the cut smelting sample is a smelted alloy ingot with a diameter ranging from 5 to 10 mm, and the diameter of the ceramic sheet is 5 to 10 mm larger than the size of the smelted alloy ingot.

[0020] In a preferred embodiment of the present invention, the leveling in step three is maintained by using a plastic material pad.

[0021] In a preferred embodiment of the present invention, the certain angle in step three is 30-45°.

[0022] In a preferred embodiment of the present invention, the number of sample negative films in step 3 is not less than 8, preferably 8-12.

[0023] In a preferred embodiment of the present invention, the preliminary processing in step 4 is to use a plane graphics processing software to straighten the photo with the skewed contact surface in step 3 and then cut off the redundant background part of the photo;

[0024] In a preferred embodiment of the present invention, the fitting process is performed using the Contact Angle plug-in in ImageJ, and the specific steps are as follows:

[0025] First, set the baseline, and then mark points around the sample according to the sample morphology. After marking, use the plug-in for automatic fitting. The plug-in will automatically calculate the contact angle of the sample based on the points and the set baseline, and get a corresponding fitting value.

[0026] In a preferred embodiment of the present invention, the secondary processing is to remove the average value of the total data of the obtained fitting values ​​after processing all the photos, remove the abnormal data if any, and then obtain the wetting angle measurement result of a sample.

[0027] In a preferred embodiment of the present invention, if there is abnormal data, the abnormal data is removed using the following criteria:

[0028] Laida criterion: Applicable to the case where the number of measurements n ≥ 10. By calculating the standard deviation s, if the absolute value of the difference between a measurement value and the average value is ≥ 3s, the value is judged as an abnormal value;

[0029] Grubbs criterion: Applicable to the case where the number of sample measurements n is greater than 3 and less than 50. By calculating the absolute value of the maximum residual and the mean value divided by the standard deviation, if the result is ≥ G(n), the value is judged as an outlier;

[0030] Dixon criterion: It is applicable to measurement data of different times and identifies outliers through different calculation methods. Its advantage is that it can eliminate outliers multiple times, but only one can be eliminated at a time.

[0031] The beneficial effects of the present invention are:

[0032] (1) The present invention does not require any complex equipment. It can measure the wetting angle using a device with a camera function such as a camera, a plastic material pad such as plasticine, and a free software. There is no need to pay extra fees for measuring and characterizing the wetting angle, thus saving experimental costs.

[0033] (2) The present invention does not involve other complicated experimental operations, such as grinding metal ingots, measuring the size of each sample, etc., nor does it involve any complicated calculations. It can improve the detection efficiency, lower the measurement threshold of wetting angle characterization, and is also conducive to processing large amounts of data.

[0034] (3) The present invention will not damage the contact surface of the sample in order to measure the wetting angle. The method of the present invention can perform completely non-destructive measurement while maintaining the morphology of the metal ingot and the ceramic sheet after smelting. It is also beneficial to perform the next step of SEM, TEM and other characterization work on the experimental sample after the wetting angle measurement.

[0035] (4) The present invention creatively applies software fitting shape technology to wetting angle measurement, solving the problem that it is difficult to measure wetting angle in large-scale, multivariate wettability research experiments. Using software for fitting can reduce difficulties such as inaccurate measurement accuracy and cumbersome measurement processes. Because of its three advantages mentioned above, such as low cost, simplicity and little damage to samples, this method has irreplaceable advantages over traditional methods in terms of time, space and cost when conducting measurement-related work on multiple samples. It is a wetting angle measurement method with progressive significance for further studying the interfacial wetting phenomenon of metals and ceramics with the help of wetting angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Geometric diagram for wetting angle measurement.

[0037] Figure 2 The present invention is a flow chart of a preferred embodiment of a method for measuring the wetting angle between a high-temperature alloy and a ceramic mold shell.

[0038] Figure 3 This is the water-cooled copper sessile drop method experimental device and schematic diagram used in this experiment.

[0039] Figure 4 (a~e) is Figure 2 A schematic diagram of the fitting photo obtained in Example 1 is shown.

[0040] Figure 5 (a~e) is Figure 2 The diagram is a schematic diagram of the fitting photo obtained in the second embodiment shown.

[0041] Figure 6 for Figure 2 The figure shows a schematic diagram of the fitting photo obtained in the third embodiment of the present invention.

[0042] Figure 7 This is a sample picture obtained by processing in the comparative example. DETAILED DESCRIPTION

[0043] In order to further understand the content of the present invention, the present invention will be described in detail below in conjunction with specific embodiments.

[0044] It should be noted that the water-cooled copper smelting furnace, crucible, image processing software, etc. used in the present invention can use existing equipment according to actual conditions, change the crucible material and image processing software, etc., and there is no special requirement for experimental conditions. In this method, it is very important to keep the contact surface between the alloy ingot and the ceramic sheet horizontal and to reasonably process the obtained fitting graph and data, which is an important key step to obtain accurate measurement and reliable wetting angle data.

[0045] The method for measuring the wetting angle between the high-temperature alloy and the ceramic mold shell of the present invention has the following beneficial effects:

[0046] (1) The present invention does not require any complex equipment. It can measure the wetting angle using a device with a camera function, plasticine and a free software. There is no need to pay extra fees for measuring and characterizing the wetting angle, thus saving experimental costs.

[0047] (2) The present invention does not involve other complicated experimental operations, such as grinding metal ingots, measuring the size of each sample, etc., nor does it involve any complicated calculations. It can improve the detection efficiency, lower the measurement threshold of wetting angle characterization, and is also conducive to processing large amounts of data.

[0048] (3) The present invention will not damage the contact surface of the sample in order to measure the wetting angle. The method of the present invention can perform completely non-destructive measurement while maintaining the morphology of the metal ingot and the ceramic sheet after smelting. It is also beneficial to perform the next step of SEM, TEM and other characterization work on the experimental sample after the wetting angle measurement.

[0049] (4) The present invention solves the problem that it is difficult to measure the wetting angle in large-scale, multivariate wettability research experiments. Because of its three advantages mentioned above, such as low cost, simplicity and little damage to samples, this method has irreplaceable advantages over traditional methods in terms of time, space and cost when conducting measurement-related work on multiple samples. It is a wetting angle measurement method with progressive significance when further studying the interfacial wetting phenomenon between metals and ceramics with the help of the wetting angle.

[0050] The following is further described in conjunction with specific embodiments.

[0051] Embodiment 1:

[0052] like Figure 1 As shown, according to a preferred embodiment of the method for measuring the wetting angle between high-temperature alloys and different types of ceramic mold shells of the present invention, the measuring method includes the following steps in chronological order:

[0053] Step 1: contacting the nickel-based high-temperature alloy with five different ceramic mold shells and performing high-temperature smelting to obtain a sample consisting of an alloy ingot and a ceramic mold shell;

[0054] Step 2: Cut the sample obtained after smelting into appropriate ceramic pieces, and process the sample so that the contact line between the ceramic piece and the metal remains horizontal;

[0055] Step 3: Take photos of the sample while keeping the horizontal line in the camera flush with the contact surface; after each photo is taken, rotate the sample at a certain angle to obtain horizontal photos of the sample in different directions, and obtain a sufficient number of sample negatives;

[0056] Step 4: Process the obtained film appropriately, and finally use the plug-in in the ImageJ software to process the corresponding wetting angle data; then process these data to obtain the final result. Some values ​​in the final result are shown in Table 1.

[0057] In step 1, the grade of the nickel-based high-temperature alloy is DD6, the ceramic mold shell is an alumina-based ceramic mold shell with 0.5-2.5% BN added, with a total of five ratios, the smelting temperature is 1600°C, and the smelting method used is the water-cooled copper drop method, and its principle diagram is as follows Figure 2 As shown, the vacuum degree during melting does not exceed 10Pa.

[0058] In step 2, after smelting, the cut ceramic piece has a diameter of 25 mm, and the bottom of the ceramic piece is polished to be flat.

[0059] In step three, the rotation angle is 22.5° each time, and photos in different orientations are obtained by changing the shooting angle, and a total of 16 photos are obtained.

[0060] In steps 2 and 3, after polishing the bottom of the ceramic sheet, adjust the height appropriately so that it is at the same level as the camera, and then confirm that the contact lines in the sample are parallel.

[0061] In step 4, first try to use PS to straighten the skewed contact surface photo in step 3, and crop the redundant part of the photo. Then use the Contact Angle in ImageJ to fit the sample in the photo, and take the supplementary angle according to the fitted graph. After processing all the photos, the average value of the obtained data is removed, and abnormal data can be removed if necessary, and then the wetting angle measurement result of a sample is obtained.

[0062] Embodiment 2:

[0063] According to another preferred embodiment of the method for measuring the wetting angle of the present invention, the process steps, the equipment used, the technical principles and the beneficial effects are basically the same as those of the first embodiment, except that:

[0064] In step 1, the grade of the nickel-based high-temperature alloy used is DZ417G, the ceramic shell is an alumina-based ceramic shell with 0.5-2.5% kaolin added, the experimental temperature is 1500°C, and the smelting method used is the water-cooled copper sessile drop method, the principle diagram of which is as follows: Figure 3 As shown, the vacuum degree during melting does not exceed 10Pa.

[0065] In step 2, after smelting, the diameter of the cut ceramic piece is 20 mm, and plasticine is used to make the contact line between the alloy melt and the ceramic shell horizontal.

[0066] In step three, the rotation angle is 30° each time, and photos in different orientations are obtained by changing the shooting angle, and a total of 12 photos are obtained.

[0067] In steps 2 and 3, after polishing the bottom of the ceramic sheet, manually press the angle of the sample in the clay so that it is at the same level as the camera, and then confirm that the contact lines in the sample are parallel.

[0068] In step 4, the sample in the photo is fitted using a plug-in in ImageJ, and the complementary angle is processed according to the fitted graph; after processing all the photos, the obtained data is averaged, and abnormal data can be removed if necessary, and then the wetting angle measurement result of a sample is obtained. The final measurement result is averaged, and some of the results are shown in Table 2.

[0069] Embodiment three:

[0070] According to another preferred embodiment of the method for measuring the wetting angle of the present invention, the process steps, the equipment used, the technical principles and the beneficial effects are basically the same as those of the first embodiment, except that:

[0071] In step 1, the alloy type used is TiAl, the ceramic shell is a barium zirconate ceramic shell, the experimental temperature is 1500°C, and the smelting method used is a water-cooled copper sessile drop method, the schematic diagram of which is shown in FIG. Figure 3 As shown, the vacuum degree during melting does not exceed 10Pa.

[0072] In step 2, after smelting, the cut ceramic piece has a diameter of 15 mm, and plasticine is used to make the contact line between the alloy melt and the ceramic shell horizontal.

[0073] In step three, the rotation angle is 40° each time, and photos in different orientations are obtained by changing the shooting angle, and a total of 9 photos are obtained.

[0074] In steps 2 and 3, after polishing the bottom of the ceramic sheet, manually press the angle of the sample in the clay so that it is at the same level as the camera, and then confirm that the contact lines in the sample are parallel.

[0075] In step 4, the sample in the photo is fitted using a plug-in in ImageJ, and the complementary angle is processed according to the fitted graph; after processing all the photos, the obtained data is averaged, and abnormal data can be removed if necessary, and then the wetting angle measurement result of a sample is obtained. The final measurement result is averaged, and some of the results are shown in Table 3.

[0076] Comparative Example:

[0077] TiNi alloy and BaZrO were prepared by sessile drop method using Bridgeman furnace.3 After smelting, several TiNi alloy ingots were inlaid, and then half of the cross section was ground off, sandpaper ground and polished. The final sample photo is as follows Figure 7 As shown, it can be seen that this process requires tedious steps such as mounting, grinding, and polishing. It takes 2 to 3 days to process a batch of samples to obtain wetting angle data, and the ingot is destroyed, making it impossible to perform other characterizations such as XRD and SEM of the bottom.

[0078] Table 1 Wetting angle test results of nickel-based high-temperature alloy samples in Example 1

[0079]

[0080] Table 2 Wetting angle test results of nickel-based high-temperature alloy samples in Example 2

[0081]

[0082]

[0083] Table 3 Wetting angle test results of TiAl in Example 3

[0084]

[0085] Special note: The technical solution of the present invention involves many parameters, and the synergy between the various parameters needs to be comprehensively considered to obtain the beneficial effects and significant progress of the present invention. Moreover, the value ranges of the various parameters in the technical solution are obtained after a large number of experiments, which is obviously creative.

[0086] It is not difficult for those skilled in the art to understand that the method for measuring the wetting angle of nickel-based high-temperature alloys of the present invention includes any combination of the invention content and specific implementation methods of the above-mentioned invention specification and the various parts shown in the drawings. Due to the limited space and to make the specification concise, the various schemes composed of these combinations are not described one by one. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A new wetting angle measurement method, characterized in that: The measuring method comprises the following steps in order Step 1: contacting the alloy ingot with the ceramic mold shell and performing high-temperature smelting to obtain a sample consisting of the alloy ingot and the ceramic mold shell; Step 2: Cut the sample obtained after smelting into appropriate ceramic pieces, and process the sample so that the contact line between the ceramic piece and the metal remains horizontal; Step 3: Take photos of the sample while keeping the horizontal line in the camera flush with the contact surface; after each photo is taken, rotate the sample at a certain angle to obtain horizontal photos of the sample in different directions, and obtain a sufficient number of sample negatives; Step 4: Process the obtained film appropriately, use wetting angle processing software to process the film to obtain corresponding wetting angle data; then process these data to obtain the final result.

2. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 1, characterized in that: The diameter of the alloy ingot in step 1 is in the range of 5 to 15 mm; The high temperature smelting is carried out in a sessile drop method using a crucible as a carrying container for the alloy ingot and the ceramic sheet.

3. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 1, characterized in that: The cut smelting sample in step 2 is a smelted alloy ingot with a diameter ranging from 5 to 10 mm, and the diameter of the ceramic sheet is 5 to 10 mm larger than the size of the smelted alloy ingot.

4. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 1, characterized in that: In the step 3, the plastic material liner is used to maintain the level; The certain angle in step 3 is 30-45°; The number of sample negatives in step 3 is not less than 8.

5. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 1, characterized in that: The preliminary processing in step 4 is to use plane graphics processing software to straighten the photo with the skewed contact surface in step 3 and then cut off the redundant background part of the photo.

6. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 1, characterized in that: The fitting process in step 4 is performed using the Contact Angle plug-in in ImageJ. The specific steps are as follows: First, set the baseline, and then mark points around the sample according to the sample morphology. After marking, use the plug-in for automatic fitting. The plug-in will automatically calculate the contact angle of the sample based on the points and the set baseline, and get a corresponding fitting value.

7. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 1, characterized in that: The secondary processing in step 4 is to remove the average value of the total data of the obtained fitting values ​​after processing all the photos, remove the abnormal data if there is any, and then obtain the wetting angle measurement result of a sample.

8. The method for measuring the wetting angle between an alloy melt and a ceramic mold shell according to claim 6, characterized in that: If there is abnormal data, the abnormal data is removed using the following criteria: Laida criterion: Applicable to the case where the number of measurements n ≥ 10. By calculating the standard deviation s, if the absolute value of the difference between a measurement value and the average value is ≥ 3s, the value is judged as an abnormal value; Grubbs criterion: Applicable to the case where the number of sample measurements n is greater than 3 and less than 50. By calculating the absolute value of the maximum residual and the mean value divided by the standard deviation, if the result is ≥ G(n), the value is judged as an outlier; Dixon criterion: It is applicable to measurement data of different times and identifies outliers through different calculation methods. Its advantage is that it can eliminate outliers multiple times, but only one can be eliminated at a time.

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