A coating long-term high-temperature bending test device and method

Abstract

The present invention discloses a long-term high-temperature bending test device and method for coatings, and belongs to the technical field of high-temperature mechanical experiments. The device includes a stress loading device, which includes a limit bracket, a replaceable test bench, a replaceable pressure head and a counterweight module; wherein the limit bracket includes a support rod and a top seat and a base, and the two ends of the support rod are respectively connected to the top seat and the base; the replaceable test bench is arranged on the side surface of the base facing the top seat; the replaceable pressure head is used to apply pressure to the coating sample to be tested placed on the replaceable test bench; the counterweight module is added to the replaceable pressure head to counterweight the replaceable pressure head. The device and the corresponding method can solve the problem of long-term high-temperature mechanical loading at a lower cost while expanding the high-temperature mechanical loading form of the coating, which is conducive to studying the long-term high-temperature evolution behavior of the coating under gradient stress conditions, and then provide a basis and guidance for the failure analysis and long-life design of the surface protective coating of the hot end components with complex configurations.

Description

Technical Field

[0001] The present invention relates to the technical field of high temperature mechanical experiments, and in particular to a device and method for a long-time high temperature bending experiment of a coating. Background Art

[0002] Ceramic and metal coatings, represented by thermal barrier and environmental barrier coatings, are key thermal protection technologies and are widely used in the surface protection of hot-end components in high-tech fields such as aerospace, energy and power, and ocean power generation. Their service conditions not only involve extremely high temperature environments, but also complex mechanical conditions such as substrate constraints, inertial forces, and aerodynamic loads. Ceramic and metal coatings that are in high-temperature conditions for a long time will undergo structural or material evolution processes such as sintering, phase change, and oxidation, which are sensitive to load conditions and stress states. Experimental research on the influence of stress on the long-term high-temperature evolution process of coatings is of great significance for the failure analysis and long-life design of surface protective coatings of complex configuration hot-end components.

[0003] At present, the thermal load application method in the field of high-temperature experimental technology is relatively mature. The uniform or gradient temperature field of the actual service condition of the coating can be simulated by various devices such as muffle furnace, halogen lamp, laser source, etc. The average temperature and temperature gradient can reach 1000℃ and 200℃ / mm respectively. However, since the coating thickness is usually small (hundreds of microns to several millimeters), the mechanical loading methods suitable for the coating in high-temperature environments are still limited.

[0004] High-temperature indentation experimental equipment can apply short-term compressive stress to the micro-area on the surface of the sample, but it is difficult to perform long-term high-temperature loading on the entire sample due to the size and material of the indenter; Thermal Mechanical Analyzer can apply three-point bending load to the coating sample, but due to the loading method and fixture size, the maximum stress applied to the sample is usually small and the experimental cost is high.

[0005] Therefore, it is necessary to develop high-temperature mechanical experimental equipment and methods suitable for coatings, so as to achieve long-term and low-cost experimental characterization of their high-temperature evolution process within a large load range.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a coating long-term high-temperature bending test device and method to solve the above-mentioned technical problems.

[0008] This application can be implemented as follows:

[0009] In a first aspect, the present application provides a coating long-term high-temperature bending test device, including a stress loading device, the stress loading device including a limit bracket, a replaceable test bench, a replaceable pressure head and a counterweight module;

[0010] The limiting bracket includes a support rod and a top seat and a base that are arranged opposite to each other, and the two ends of the support rod are connected to the top seat and the base respectively;

[0011] The replaceable test table is arranged on a side surface of the base facing the top seat;

[0012] The replaceable pressure head is used to apply pressure to the coating sample to be tested placed on the replaceable test bench; the weight module is added to the replaceable pressure head to balance the weight of the replaceable pressure head.

[0013] In an optional embodiment, there are multiple support rods, and the multiple support rods are arranged along the edges of the top seat and the base, and the edge of the replaceable test bench abuts against the support rods.

[0014] In an optional embodiment, a plurality of support rods are arranged at equal intervals.

[0015] In an optional embodiment, the replaceable test bench includes a test bench body and a contact member;

[0016] The test bench body is located on a side surface of the base facing the top seat, and the edge of the test bench body abuts against the support rod; the contact piece is arranged on the upper surface of the test bench body to provide a contact point for the coating sample to be tested.

[0017] In an optional embodiment, the contact member includes a first contact strip and a second contact strip, and the first contact strip and the second contact strip are symmetrically arranged with the center of the test bench body as a symmetry axis;

[0018] Or, the contact member includes a first contact ball, a second contact ball and a third contact ball, the first contact ball, the second contact ball and the third contact ball are arranged at equal intervals and the distances between the center of the first contact ball, the center of the second contact ball and the center of the third contact ball and the center of the test bench body are equal.

[0019] In an optional embodiment, the replaceable pressure head includes a pressure portion, a connecting rod and a bearing portion;

[0020] A limiting hole is provided on the top seat, and the pressurizing part is used to contact the surface of the coating sample to be tested during the experiment. One end of the connecting rod is connected to the pressurizing part, and the other end passes through the limiting hole and extends in a direction away from the base and is connected to the bearing part; the counterweight module is carried by the bearing part.

[0021] In an optional embodiment, the axis of the connecting rod, the center of the limiting hole, the center of the test bench body, the center of the bearing portion and the center of the counterweight module are all collinear.

[0022] In an optional embodiment, the pressurizing portion is in a truncated cone shape;

[0023] When the contact element includes a first contact strip and a second contact strip, the pressurizing portion is in the shape of a positive truncated cone with a small top and a large bottom, and the bottom of the pressurizing portion also has a third contact strip and a fourth contact strip to cooperate with the first contact strip and the second contact strip to form four contact sites for the coating sample to be tested;

[0024] When the contact member includes the first contact ball, the second contact ball and the third contact ball, the pressing portion is in the shape of an inverted frustum of a cone with a larger top and a smaller bottom.

[0025] In an optional embodiment, the third contact strip and the fourth contact strip are symmetrically arranged with the center of the test bench body as a symmetry axis.

[0026] In an optional embodiment, the contact position between the lower end of the inverted truncated cone-shaped pressurizing portion and the coating sample to be tested is the center position of the test bench body.

[0027] In an optional embodiment, the counterweight module is in a ring shape, and the counterweight module passes through the connecting rod and is loaded on the bearing part.

[0028] In an optional embodiment, the stress loading device is made of high temperature structural ceramics by sintering or additive manufacturing.

[0029] In alternative embodiments, the high temperature structural ceramic comprises aluminum oxide or silicon carbide.

[0030] In an optional embodiment, the coating long-term high-temperature bending test device further includes a heating device, and the heating device is used to heat the coating sample to be tested.

[0031] In alternative embodiments, the heating device comprises a muffle furnace, a halogen lamp, or a laser source.

[0032] In the second aspect, the present application provides a coating long-term high-temperature bending test method, comprising the following steps: using any of the aforementioned embodiments of the coating long-term high-temperature bending test device, applying a constant bending load to the coating sample to be tested through a stress loading device and simultaneously heating the coating sample to be tested through a heating device, so that the coating sample to be tested forms a gradient stress field along the thickness direction in a high-temperature environment.

[0033] In an optional embodiment, the stress loading device applies a constant bending load to the coating sample to be tested in a uniaxial bending mode and a biaxial bending mode; wherein the uniaxial bending mode corresponds to a four-point bending loading mode, and the biaxial bending mode corresponds to a piston-three-ball loading mode.

[0034] In an optional embodiment, when a four-point bending loading method is adopted, the coating sample to be tested is in the shape of a long strip, the contact member includes a first contact strip and a second contact strip, the pressurizing portion is in the shape of a positive truncated cone with a small top and a large bottom, and the bottom of the pressurizing portion also has a third contact strip and a fourth contact strip to cooperate with the first contact strip and the second contact strip to form four contact sites for the coating sample to be tested;

[0035] The corresponding extreme value of tensile stress or compressive stress is calculated as follows: 3PL / 4wb 2 ; Wherein, P is the total gravity of the replaceable pressure head and the counterweight module, L is the distance between the contact point between the first contact strip and the coating sample to be tested and the contact point between the second contact strip and the coating sample to be tested, w is the width of the coating sample to be tested, and b is the thickness of the coating sample to be tested.

[0036] In an optional embodiment, the distance between the contact point between the third contact strip and the coating sample to be tested and the contact point between the second contact strip and the coating sample to be tested is half of L.

[0037] In an optional embodiment, when a piston-three-ball loading method is adopted, the coating sample to be tested is circular, and the contact member includes a first contact ball, a second contact ball and a third contact ball, and the first contact ball, the second contact ball and the third contact ball are arranged at equal intervals, and the center of the first contact ball, the center of the second contact ball and the center of the third contact ball are at the same distance from the center of the test bench body; the pressurizing part is in an inverted frustum shape with a larger upper part and a smaller lower part, and the contact position of the lower end of the pressurizing part and the coating sample to be tested is the center position of the test bench body; the first contact ball, the second contact ball, the third contact ball and the lower end of the pressurizing part cooperate to form four contact points for the coating sample to be tested;

[0038] The corresponding extreme value of tensile stress or compressive stress is calculated as follows: 0.2387P(XY)b 2 ; where X and Y are (1+v)[1+ln(r1 / r3) 2 ]+(1-v)(r1 / r3) 2 and (1+v)ln(r2 / r3) 2 +[(1-v) / 2](r2 / r3) 2 ; P is the total gravity of the replaceable pressure head and the counterweight module, b is the thickness of the coating sample to be tested, v is the Poisson's ratio of the coating sample to be tested, r1 is the radius of the circle where the first contact ball, the second contact ball and the third contact ball are located, r2 is the radius of the contact surface between the lower end of the pressurizing part and the coating sample to be tested, and r3 is the radius of the coating sample to be tested.

[0039] The beneficial effects of this application include:

[0040] The long-term high-temperature bending test device for coatings provided by the present application is a device that matches a limit bracket, a replaceable test bench, a replaceable pressure head and a counterweight module, and the counterweight module is added to the replaceable pressure head to counterweight the replaceable pressure head, and the replaceable pressure head applies pressure (constant bending load) to the coating sample to be tested placed on the replaceable test bench, so that a long-term stable gradient stress field can be formed in the thickness direction of the coating sample to be tested. The experimental device has a simple structure, low manufacturing and use costs, and can characterize the effects of two different stress states of tension and compression on high-temperature evolution behavior on a sample as needed, which is conducive to the high-throughput characterization of complex stress action laws.

[0041] The corresponding experimental method is simple and easy to implement. Single-axis and double-axis bending loading is conducive to forming a large stress gradient inside the small-sized coating sample to be tested, and the coating sample can be heated with the help of existing muffle furnaces, halogen lamps, laser sources and other devices, which is conducive to reducing the experimental hardware and operating costs. In addition, by using different replaceable test benches and replaceable pressure heads, different forms of high-temperature mechanical experiments such as single-axis and double-axis bending can be carried out, which is conducive to expanding the high-temperature mechanical loading forms of coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A schematic diagram of the structure of the long-term high-temperature bending test device for coatings in a uniaxial bending mode provided in the present application at a first viewing angle;

[0044] Figure 2 A schematic diagram of the structure of the coating long-term high-temperature bending test device in the uniaxial bending mode provided in the present application at a second viewing angle;

[0045] Figure 3 A schematic diagram of the structure of the coating long-time high-temperature bending test device in the uniaxial bending mode provided in the present application from a third viewing angle;

[0046] Figure 4 A schematic structural diagram of a coating long-time high-temperature bending test device in a uniaxial bending mode provided in the present application at a fourth viewing angle;

[0047] Figure 5 A schematic diagram of the structure of the long-term high-temperature bending test device for coatings in a biaxial bending mode provided in the present application at a first viewing angle;

[0048] Figure 6A schematic diagram of the structure of the long-term high-temperature bending test device for coatings in a biaxial bending mode provided in the present application at a second viewing angle;

[0049] Figure 7 A schematic diagram of the structure of the long-term high-temperature bending test device for coatings in a biaxial bending mode provided in the present application from a third viewing angle;

[0050] Figure 8 A schematic structural diagram of a coating long-time high-temperature bending test device in a biaxial bending mode provided in the present application at a fourth viewing angle;

[0051] Fig. 9 This is a cross-sectional microstructure diagram of the upper portion of a coating sample that has undergone a long-term high-temperature bending test in the application example of this application;

[0052] Fig.10 This is a cross-sectional microstructure diagram of the lower part of the coating sample that has undergone a long-term high-temperature bending test in the application example of this application.

[0053] Icons: 11-top seat; 111-limiting hole; 12-base; 13-support rod; 21-test bench body; 221-first contact strip; 222-second contact strip; 223-first contact ball; 224-second contact ball; 225-third contact ball; 31-pressurizing part; 311-third contact strip; 312-fourth contact strip; 32-connecting rod; 33-bearing part; 40-weight module; 5-coating sample to be tested. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0055] The long-term high-temperature bending test device and method for coatings provided in this application are described in detail below.

[0056] Please refer to Figures 1 to 8 , the present application proposes a coating long-term high-temperature bending test device, including a stress loading device, the stress loading device includes a limit bracket, a replaceable test bench, a replaceable pressure head and a counterweight module 40;

[0057] The limiting bracket includes a support rod 13 and a top seat 11 and a base 12 arranged opposite to each other, and both ends of the support rod 13 are connected to the top seat 11 and the base 12 respectively;

[0058] The replaceable test bench is arranged on a side surface of the base 12 facing the top base 11;

[0059] The replaceable pressure head is used to apply pressure to the coating sample 5 to be tested placed on the replaceable test bench; the weight module 40 is added to the replaceable pressure head to balance the weight of the replaceable pressure head.

[0060] For reference, the top seat 11 and the base 12 are of the same shape and size, and the cross-sections of the two are both circular. The top seat 11 and the base 12 overlap in vertical projection.

[0061] There are multiple support rods 13, which are arranged along the edges (also understood as the circumferential direction) of the top seat 11 and the base 12, and the edge of the replaceable test bench abuts against the support rods 13. In a preferred embodiment, the multiple support rods 13 are arranged at equal intervals.

[0062] The support rods 13 can provide support for the replaceable test bench, the replaceable pressure head, the counterweight module 40, etc. At the same time, the support rods 13 can also constrain the in-plane displacement of the replaceable test bench.

[0063] Optionally, the support rod 13, the top seat 11 and the base 12 may be formed integrally, or may be connected and fixed by conventional connection methods (such as snap connection, bonding, etc.).

[0064] In the present application, the replaceable test bench includes a test bench body 21 and a contact member;

[0065] The test bench body 21 is located on a side surface of the base 12 facing the top seat 11 , and the edge of the test bench body 21 abuts against the support rod 13 ; the contact member is arranged on the upper surface of the test bench body 21 to provide a contact point for the coating sample 5 to be tested.

[0066] For reference, the cross section of the test bench body 21 may also be circular, and its center is colinear with the center of the base 12. The contact piece protrudes upward from the upper surface of the test bench body 21, and contacts with the coating sample 5 to be tested placed on the test bench body 21 to support it.

[0067] In some embodiments, Figures 1 to 3 The contact member includes a first contact strip 221 and a second contact strip 222 . The first contact strip 221 and the second contact strip 222 are symmetrically arranged with the center of the test bench body 21 as the symmetry axis and are arranged at a position close to the edge of the test bench body 21 .

[0068] In other embodiments, Figures 5 to 7 The contact member includes a first contact ball 223, a second contact ball 224 and a third contact ball 225. The first contact ball 223, the second contact ball 224 and the third contact ball 225 are arranged at equal intervals and the center of the first contact ball 223, the center of the second contact ball 224 and the center of the third contact ball 225 are at the same distance from the center of the test bench body 21.

[0069] It can also be understood that the circular shapes of the first contact ball 223, the second contact ball 224 and the third contact ball 225 can form a circle together. The first contact ball 223, the second contact ball 224 and the third contact ball 225 are of the same size.

[0070] In the present application, the replaceable pressure head includes a pressure portion 31 , a connecting rod 32 , and a bearing portion 33 ;

[0071] The top seat 11 is provided with a limiting hole 111, and the pressurizing part 31 is used to contact the surface of the coating sample 5 to be tested during the experiment. One end of the connecting rod 32 is connected to the pressurizing part 31, and the other end passes through the limiting hole 111 and extends in a direction away from the base 12 and is connected to the bearing part 33; the counterweight module 40 is carried by the bearing part 33.

[0072] The axis of the connecting rod, the center of the stop hole 111, the center of the test bench body 21, the center of the bearing portion 33 and the center of the counterweight module 40 are all collinear. Preferably, the center of the circle where the multiple support rods 13 are located coincides with the center of the stop hole 111. Through the above arrangement, the replaceable indenter and the replaceable test bench can always be vertically aligned, thereby meeting the uniaxial or biaxial bending loading conditions.

[0073] In addition, the setting of the limiting hole 111 can also constrain the displacement of the replaceable pressing head in the surface (ie, in the horizontal direction), and only allow it to move in the vertical direction.

[0074] In the present application, the pressurizing portion 31 is in a truncated cone shape as a whole, and the truncated cone shape is in a positive direction and a negative direction respectively according to different test requirements.

[0075] Specifically, when the contact member includes the first contact strip 221 and the second contact strip 222, the pressurizing portion 31 is in the shape of a positive truncated cone with a small top and a large bottom, and the bottom of the pressurizing portion 31 also has a third contact strip 311 and a fourth contact strip 312 (such as Figure 1 ) to cooperate with the first contact strip 221 and the second contact strip 222 to form four contact sites for the coating sample 5 to be tested;

[0076] Preferably, the third contact bar 311 and the fourth contact bar 312 are symmetrically arranged with the center of the test bench body 21 as the symmetry axis. The third contact bar 311 and the fourth contact bar 312 protrude downward from the bottom of the pressurizing portion 31 to form contact with the coating sample 5 to be tested thereunder to apply a mechanical load.

[0077] When the contact member includes the first contact ball 223 , the second contact ball 224 and the third contact ball 225 , the pressing portion 31 is in the shape of an inverted truncated cone with a larger top and a smaller bottom.

[0078] Preferably, the contact position between the lower end of the inverted truncated cone-shaped pressurizing portion 31 and the coating sample 5 to be tested is the center position of the test bench body 21 .

[0079] It can also be understood that: in the present application, the stress loading device applies a constant bending load to the coating sample 5 to be tested in a uniaxial bending mode and a biaxial bending mode; wherein the uniaxial bending mode corresponds to a four-point bending loading mode, and the biaxial bending mode corresponds to a piston-three-ball loading mode. When the contact member is a contact strip, it corresponds to a four-point bending loading mode (uniaxial bending mode), and when the contact member is a contact ball, it corresponds to a piston-three-ball loading mode (biaxial bending mode).

[0080] It should be noted that among the basic mechanical loading modes such as tension, compression, bending and shear, uniaxial and biaxial bending loads can form a gradient stress field in the thickness direction of the coating sample. One sample can simultaneously characterize the influence of two different stress states of tension and compression on the high-temperature evolution behavior, which is conducive to the high-throughput characterization of complex stress action laws.

[0081] Furthermore, in the present application, the counterweight module 40 is in a circular ring shape, and the counterweight module 40 passes through the connecting rod 32 and is loaded on the bearing portion 33 .

[0082] Specifically, the counterweight module 40 can be stacked by a plurality of stackable unit circular ring blocks as required, that is, they can be nested outside the connecting rod 32 and carried on the bearing portion 33 in a stacked manner. In a specific experiment, according to the uniaxial and biaxial test modes and the required stress gradient, the required total weight of the counterweight module 40 is calculated by the following extreme value calculation formulas of tensile stress or compressive stress, respectively. The counterweight module 40 and the replaceable indenter are used together to load the coating sample 5 to be tested by gravity.

[0083] The stress loading devices can be manufactured by sintering or additive manufacturing of high temperature structural ceramics, wherein the high temperature structural ceramics may exemplarily include aluminum oxide or silicon carbide.

[0084] The stress loading device in the present application can be used to perform uniaxial or biaxial loading high temperature bending mechanics experiments for hundreds of hours in a high temperature environment above 1000°C.

[0085] Furthermore, the coating long-term high-temperature bending test device provided in the present application also includes a heating device (not shown), which is used to heat the coating sample 5 to be tested.

[0086] For reference, the heating device may illustratively include a muffle furnace, a halogen lamp, or a laser source.

[0087] Correspondingly, the present application also provides a coating long-term high-temperature bending test method, comprising the following steps: using the above-mentioned coating long-term high-temperature bending test device, applying a constant bending load to the coating sample 5 to be tested through a stress loading device and simultaneously heating the coating sample 5 to be tested through a heating device, so that the coating sample 5 to be tested forms a gradient stress field along the thickness direction in a high-temperature environment.

[0088] The coating sample 5 to be tested may be a thermal barrier and environmental barrier coating, for example.

[0089] For reference, the stress loading device applies a constant bending load to the coating sample 5 to be tested in a uniaxial bending mode and a biaxial bending mode; wherein the uniaxial bending mode corresponds to a four-point bending loading mode, and the biaxial bending mode corresponds to a piston-three-ball loading mode.

[0090] When the four-point bending loading method is adopted, the coating sample 5 to be tested is in the shape of a long strip, the contact member includes a first contact strip 221 and a second contact strip 222, the pressurizing portion 31 is in the shape of a positive frustum with a small top and a large bottom, and the bottom of the pressurizing portion 31 also has a third contact strip 311 and a fourth contact strip 312 to cooperate with the first contact strip 221 and the second contact strip 222 to form four contact points for the coating sample 5 to be tested; a gradient uniaxial stress field is formed along the thickness direction of the coating sample 5 to be tested.

[0091] The corresponding extreme value of tensile stress or compressive stress is calculated as follows: 3PL / 4wb 2 ; Wherein, P is the total gravity of the replaceable pressure head and the counterweight module 40, L is the distance between the contact point between the first contact strip 221 and the coating sample 5 to be tested and the contact point between the second contact strip 222 and the coating sample 5 to be tested, w is the width of the coating sample 5 to be tested, and b is the thickness of the coating sample 5 to be tested.

[0092] The distance between the contact point between the third contact strip 311 and the coating sample 5 to be tested and the contact point between the second contact strip 222 and the coating sample 5 to be tested is half of L (ie, L / 2).

[0093] When the piston-three-ball loading method is adopted, the coating sample 5 to be tested is circular, and the contact member includes a first contact ball 223, a second contact ball 224 and a third contact ball 225. The first contact ball 223, the second contact ball 224 and the third contact ball 225 are arranged at equal intervals, and the center of the first contact ball 223, the center of the second contact ball 224 and the center of the third contact ball 225 are at the same distance from the center of the test bench body 21; the pressurizing part 31 is an inverted frustum of a cone with a larger upper part and a smaller lower part, and the contact position of the lower end of the pressurizing part 31 with the coating sample 5 to be tested is the center position of the test bench body 21; the first contact ball 223, the second contact ball 224, the third contact ball 225 and the lower end of the pressurizing part 31 cooperate to form four contact points with the coating sample 5 to be tested; and a gradient biaxial stress field is formed along the thickness direction of the coating sample 5 to be tested.

[0094] The corresponding extreme value of tensile stress or compressive stress is calculated as follows: 0.2387P(XY)b 2 ; where X and Y are (1+v)[1+ln(r1 / r3) 2 ]+(1-v)(r1 / r3) 2 and (1+v)ln(r2 / r3) 2 +[(1-v) / 2](r2 / r3) 2 ; P is the total gravity of the replaceable pressure head and the counterweight module 40, b is the thickness of the coating sample 5 to be tested, v is the Poisson's ratio of the coating sample 5 to be tested, r1 is the radius of the circle in which the first contact ball 223, the second contact ball 224 and the third contact ball 225 are located, r2 is the radius of the contact surface between the lower end of the pressurizing part 31 and the coating sample 5 to be tested, and r3 is the radius of the coating sample 5 to be tested.

[0095] As a reference, the operation process of the long-term high-temperature bending test method for coatings provided in the present application can be referred to as follows: first, a uniaxial or biaxial mode is selected according to the required stress state of the coating sample 5 to be tested; then the corresponding replaceable test bench and the replaceable pressure head are installed on the limit bracket, and the limit hole 111 on the limit bracket and the support rod 13 ensure that the replaceable test bench and the replaceable pressure head are aligned; then, according to the uniaxial or biaxial mode, the strip or circular coating sample 5 to be tested is placed on the replaceable test bench, and the height of the replaceable pressure head is lowered until it contacts the coating sample; according to the uniaxial or biaxial mode, the required total weight of the counterweight module 40 is calculated by the corresponding tensile and compressive stress extreme value formulas, and the counterweight module 40 is placed on the replaceable pressure head, and a constant bending load is applied to the coating sample 5 to be tested, and a gradient stress field is formed along the thickness direction of the coating sample 5 to be tested; the coating sample 5 to be tested is heated by devices including but not limited to a muffle furnace, a halogen lamp, a laser source, etc., so as to achieve long-term and low-cost gradient stress loading of the coating sample 5 to be tested in a high-temperature environment.

[0096] As mentioned above, the long-term high-temperature bending test device and method for coatings provided in this application have a simple structure and low manufacturing and use costs. By applying a constant bending load, a long-term stable gradient stress field is formed in the thickness direction of the coating sample 5 to be tested. The influence of two different stress states, tension and compression, on the high-temperature evolution behavior can be simultaneously characterized on one sample, which is conducive to the high-throughput characterization of complex stress action laws; the experimental method is simple and easy, and single-axis and double-axis bending loading is conducive to the formation of a large stress gradient inside the small-sized coating sample 5 to be tested, and the coating sample can be heated with the help of existing muffle furnaces, halogen lamps, laser sources and other devices, which is conducive to reducing experimental hardware and operating costs. In addition, by using different replaceable bases 12 and replaceable pressure heads, different forms of high-temperature mechanical experiments such as single-axis and double-axis bending can be carried out, which is conducive to expanding the high-temperature mechanical loading form of the coating.

[0097] Application Example 1

[0098] The coating long-term high-temperature bending test device and method provided in the present application are used to conduct a long-term high-temperature bending test on the coating sample 5 to be tested, as follows:

[0099] S1. Pretreatment: The thermal barrier coating was prepared by using the melted and crushed powder of Meike 204NS through an F4 plasma spray gun in an atmospheric environment. After being corroded by 30% concentrated hydrochloric acid for 6 hours, the substrate was peeled off to obtain a coating sample (thickness 0.4 mm, width 5 mm, length 30 mm).

[0100] S2. Mode selection: Use the coating long-term high-temperature bending test device provided in this application, uniaxial mode, and a span (L) of 20 mm.

[0101] S3. Mechanical loading: Place the coating sample pre-treated in step S1 on the replaceable test bench of the coating long-term high-temperature bending test device in S2, lower the replaceable pressure head until it contacts the coating sample, and place a counterweight module 40 on the replaceable pressure head with a load of 1.6N.

[0102] S4. High temperature experiment: Place the device and the coating sample as a whole in a muffle furnace, raise the temperature to 1200℃ at a rate of 10℃ / min for 20h high temperature experiment, and then cool it to room temperature at a rate of 10℃ / min and take out the coating sample.

[0103] S5. Sample characterization: The coating samples were prepared by vacuum cold mounting method for metallographic specimens, and the surface roughness was reduced to below 1 μm according to the standard metallographic polishing process to observe the evolution of coating microstructure and mechanical properties.

[0104] The cross-sectional microstructure of the coating after long-term high-temperature bending test is shown in Figure 2. Fig. 9 and Fig.10 shown. Fig. 9It shows that the sintering of the upper part of the coating sample is accelerated under the action of compressive stress, the porosity is low, and the microcracks between the layers are well healed; Fig.10 It shows that the sintering of the lower part of the coating sample slows down under the action of tensile stress, the porosity is high, and most of the microcracks between the layers remain open and unhealed.

[0105] The average porosity and elastic modulus results obtained by the imaging method and nanoindentation method are shown in Table 1 and Table 2, respectively.

[0106] Table 1 Cross-sectional porosity of coating samples after high temperature bending test

[0107]

[0108] Table 2 Elastic modulus of the coating sample section after high temperature bending test

[0109]

[0110] It can be seen from Tables 1 and 2 that the gradient stress field formed by the uniaxial bending load has a significant effect on the high-temperature evolution behavior of the coating sample: the sintering in the tensile stress zone is slowed down, the porosity is higher, and the elastic modulus is lower, while the sintering in the compressive stress zone is accelerated, the porosity is lower, and the elastic modulus is higher.

[0111] Above Fig. 9 , Fig.10 The results shown in Table 1 and Table 2 are consistent with the theoretical results of the effect of the gradient stress field formed by the uniaxial bending load on the high-temperature evolution behavior of the coating sample, indicating that the long-term high-temperature bending experimental device and method for the coating provided in the present application are accurate and feasible, and can realize long-term and low-cost experimental characterization of its high-temperature evolution process within a large load range.

[0112] In summary, the device and method provided in this application can expand the high-temperature mechanical loading form of the coating while solving the problem of long-term high-temperature mechanical loading at a lower cost, which is conducive to studying the long-term high-temperature evolution behavior of the coating under gradient stress conditions, and thus provide a basis and guidance for the failure analysis and long-life design of surface protective coatings of complex configuration hot end components.

[0113] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A coating long-term high-temperature bending test device, characterized in that: It includes a stress loading device, which includes a limit bracket, a replaceable test bench, a replaceable pressure head and a counterweight module; Wherein, the position-limiting bracket comprises a support rod and a top seat and a base disposed opposite to each other, and two ends of the support rod are respectively connected to the top seat and the base; The replaceable test bench is arranged on a side surface of the base facing the top seat; The replaceable pressure head is used to apply pressure to the coating sample to be tested placed on the replaceable test bench; the weight module is added to the replaceable pressure head to balance the weight of the replaceable pressure head; The replaceable test bench includes a test bench body and a contact member; The test bench body is located on a side surface of the base facing the top seat, and the edge of the test bench body abuts against the support rod; the contact member is arranged on the upper surface of the test bench body to provide a contact point for the coating sample to be tested; The contact element comprises a first contact strip and a second contact strip, wherein the first contact strip and the second contact strip are symmetrically arranged with the center of the test bench body as a symmetry axis; Or, the contact member includes a first contact ball, a second contact ball and a third contact ball, the first contact ball, the second contact ball and the third contact ball are arranged at equal intervals, and the center of the first contact ball, the center of the second contact ball and the center of the third contact ball are at the same distance from the center of the test bench body; The replaceable pressure head includes a pressure-applying portion, a connecting rod and a bearing portion; The top seat is provided with a limiting hole, the pressurizing part is used to contact the surface of the coating sample to be tested during the experiment, one end of the connecting rod is connected to the pressurizing part, and the other end passes through the limiting hole and extends in a direction away from the base and connected to the bearing part; the counterweight module is carried by the bearing part; The pressurizing portion is in a truncated cone shape; When the contact member includes a first contact strip and a second contact strip, the pressurizing portion is in the shape of a positive truncated cone with a small top and a large bottom, and the bottom of the pressurizing portion further includes a third contact strip and a fourth contact strip to cooperate with the first contact strip and the second contact strip to form four contact points for the coating sample to be tested; When the contact member includes a first contact ball, a second contact ball and a third contact ball, the pressurizing portion is in the shape of an inverted frustum of a cone with a larger top and a smaller bottom.

2. The coating long-term high-temperature bending test device according to claim 1 is characterized in that: There are multiple support rods, which are arranged along the edges of the top seat and the base, and the edges of the replaceable test table abut against the support rods.

3. The coating long-term high-temperature bending test device according to claim 2 is characterized in that: The plurality of support rods are arranged at equal intervals.

4. The coating long-term high-temperature bending test device according to claim 1 is characterized in that: The axis of the connecting rod, the center of the limiting hole, the center of the test bench body, the center of the bearing part and the center of the counterweight module are all collinear.

5. The coating long-term high-temperature bending test device according to claim 1 is characterized in that: The third contact strip and the fourth contact strip are symmetrically arranged with the center of the test bench body as a symmetry axis.

6. The coating long-term high-temperature bending test device according to claim 1 is characterized in that: The contact position between the lower end of the inverted truncated cone-shaped pressurizing portion and the coating sample to be tested is the center position of the test bench body.

7. The coating long-term high-temperature bending test device according to claim 1 is characterized in that: The counterweight module is in a circular ring shape, passes through the connecting rod and is loaded on the bearing part.

8. The coating long-term high-temperature bending test device according to claim 1 is characterized in that: The stress loading device is manufactured by sintering or additive manufacturing of high temperature structural ceramics.

9. The coating long-term high-temperature bending test device according to claim 8, characterized in that: The high temperature structural ceramics include aluminum oxide or silicon carbide.

10. The coating long-term high-temperature bending test device according to any one of claims 1 to 9, characterized in that: The coating long-term high-temperature bending test device also includes a heating device, which is used to heat the coating sample to be tested.

11. The coating long-term high-temperature bending test device according to claim 10, characterized in that: The heating device includes a muffle furnace, a halogen lamp or a laser source.

12. A coating long-term high-temperature bending test method, characterized in that: The method comprises the following steps: using the coating long-time high-temperature bending test device described in any one of claims 1 to 11, applying a constant bending load to the coating sample to be tested through a stress loading device and simultaneously heating the coating sample to be tested through a heating device, so that the coating sample to be tested forms a gradient stress field along the thickness direction in a high-temperature environment.

13. The coating long-term high-temperature bending test method according to claim 12, characterized in that: The stress loading device applies a constant bending load to the coating sample to be tested in a uniaxial bending mode and a biaxial bending mode; wherein the uniaxial bending mode corresponds to a four-point bending loading mode, and the biaxial bending mode corresponds to a piston-three-ball loading mode.

14. The coating long-term high-temperature bending test method according to claim 13, characterized in that: When the four-point bending loading method is adopted, the coating sample to be tested is in the shape of a long strip, the contact member includes a first contact strip and a second contact strip, the pressurizing portion is in the shape of a positive truncated cone with a small top and a large bottom, and the bottom of the pressurizing portion also has a third contact strip and a fourth contact strip to cooperate with the first contact strip and the second contact strip to form four contact points for the coating sample to be tested; The corresponding extreme value of tensile or compressive stress is calculated as follows: PL / 4 wb 2 ; in, P is the total weight of the replaceable pressure head and the counterweight module, L is the distance between the contact point between the first contact strip and the coating sample to be tested and the contact point between the second contact strip and the coating sample to be tested, w is the width of the coating sample to be tested, b is the thickness of the coating sample to be tested.

15. The coating long-term high-temperature bending test method according to claim 14, characterized in that: The distance between the contact point between the third contact strip and the coating sample to be tested and the contact point between the second contact strip and the coating sample to be tested is L half.

16. The coating long-term high-temperature bending test method according to claim 13, characterized in that: When the piston-three-ball loading method is adopted, the coating sample to be tested is circular, and the contact member includes a first contact ball, a second contact ball and a third contact ball, which are arranged at equal intervals and the center of the first contact ball, the center of the second contact ball and the center of the third contact ball are at the same distance from the center of the test bench body; the pressurizing part is in the shape of an inverted frustum with a larger top and a smaller bottom, and the contact position of the lower end of the pressurizing part with the coating sample to be tested is the center position of the test bench body; the first contact ball, the second contact ball, the third contact ball and the lower end of the pressurizing part cooperate to form four contact points with the coating sample to be tested; The corresponding extreme value of tensile or compressive stress is calculated as follows: 0.2387 P ( X - Y ) b 2 ; in, X and Y Respectively (1+ v )[1+ln( r 1 / r 3) 2 ]+(1- v )( r 1 / r 3) 2 and (1+ v )ln( r 2 / r 3) 2 +[(1- v ) / 2]( r 2 / r 3) 2 ; P is the total weight of the replaceable pressure head and the counterweight module, b is the thickness of the coating sample to be tested, v is the Poisson’s ratio of the coating sample to be tested, r 1 is the radius of the circle where the first contact ball, the second contact ball and the third contact ball are located. r 2 is the radius of the contact surface between the lower end of the pressurizing part and the coating sample to be tested, r 3 is the radius of the coating sample to be tested.

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