KR20100103196A - Evaluation method and instrument of high temperature indentation, thermal shock and hot corrosion - Google Patents

Abstract

PURPOSE: A method and a device for evaluating properties of damage occurred by thermal shock, high-temperature corrosion, and a contact load are provided to apply thermal shock to a sample in a short time. CONSTITUTION: A method and a device for evaluating properties of damage occurred by thermal shock, high-temperature corrosion, and a contact load is as follows. An electric furnace(22) composed of a heating body(21) and a fireproof material is formed in order to maintain high temperature. A load cell(11) for applying a load to the top of the electric furnace is formed. A ceramic tube(12) with excellent resistance to high-temperature is formed. An indenter applying a load to the ceramic tube, and a support(13) supporting a sample are formed.

Description

Method for evaluating damage characteristics due to contact load at high temperature, thermal shock and high temperature corrosion and its device {Evaluation method and instrument of high temperature indentation, thermal shock and hot corrosion}

The present invention can apply pressure in a single axis at a high temperature in order to predict the life of the machine operating in contact with each other at a high temperature in advance, the test piece can be taken out from high temperature to room temperature by using a motor and a belt, flowing a corrosive gas The present invention relates to a method for designing, fabricating, and utilizing a device capable of controlling the atmosphere of a specimen to evaluate damage caused by contact load at high temperature, thermal shock, and corrosion caused by high temperature corrosion.

Mechanical systems such as various thermal plants, chemical plants, and gas turbines in Korea are operating in high temperature environments to enhance various chemical reactions or energy efficiency, and not at room temperature, and their operating temperatures are increasingly associated with the rise of energy and environmental issues. There is a growing trend. In addition, various industrial sites use gas, fuel, etc. to operate mechanical systems, and various parts are engaged with each other to produce desired reactions or convert them into other energy through various mechanical actions and movements.

At this time, the parts interacting to operate the mechanical system are often engaged with other parts by some constant force, so that the mutual contact occurs to operate under a constant load. In addition, after a certain period of time operating and operating a thermal plant, a chemical plant, a gas turbine system at a high temperature, the cooling process for a certain time to cool the parts. This operation and operation is carried out by systematic management, but the system can be instantaneously cooled from high temperature due to intermittent electricity interruption or operator's mistake, so that a large temperature change (thermal shock) is applied to the operating parts. Can be set to. In addition, such an environment is often an environment in which various uses such as fuel and various chemical reactions occur.

Therefore, the interacting mechanical parts are contacted under a certain load, causing wear or contact load at any critical load, and when a large force is applied due to force majeure, severe wear or breakage may occur, and periodic / semi-periodic load is applied. Fatigue can lead to breakage due to prolonged use even under stresses lower than the strength of the constituent material. In addition, when exposed to high temperature for a long time, deterioration of the component material can be reduced, especially when the component material exposed to high temperature suddenly cooled due to thermal shock, etc., the inherent characteristics rapidly decrease and sometimes breakage and destruction occurs. When exposed to corrosive gases at high temperatures, the erosion and wear of materials can be accompanied, and the inherent mechanical properties can be drastically degraded.

Patents related to device design for evaluation at such a high temperature include Korean Patent Registration No. 10-0637724-0000 (name of the invention; thermal shock test apparatus for electronic parts), and Korean Patent Registration No. 20-0412679-0000 ( Name of Invention; Thermal Shock Tester), Korean Patent Registration No. 10-0595835-0000 (Name of Invention; Thermal Shock Tester), Korean Utility Model Publication No. 1997-0001328 (Invention; Repetitive High Temperature Corrosion Tester) ), Etc. are introduced. Patents related to the indentation evaluation method include Korean Patent Registration No. 10-0766394 (name of the invention: automatic indentation inspection device), Korean Patent Registration No. 10-0805873-0000 (name of the invention: Automatic indentation inspection of LCD panels Device). However, these devices are completely different from the purpose of this study, and there is no patent application regarding a device that simultaneously evaluates characteristics at high temperatures.

Although the damage caused by contact damage, thermal shock, and high temperature corrosion of mechanical parts operating at such a high temperature is in danger of shutting down the system in the domestic industry, the proper evaluation method and equipment or evaluation method suitable for the actual environment are not introduced. Anticipation of deterioration due to damage and development of related component materials are difficult, or due to breakage of some components, efforts and costs are required to repair the system. For this reason, the damage or abrasion of parts during the introduction of loads due to contact damage at high temperatures, the analysis of microcracks, the analysis of cracks that may occur due to thermal shock, the weight loss due to high-temperature corrosion or the consideration of defects are not systematically performed. Because.

It is difficult to identify the damage caused by contact with the existing equipment that measures tensile strength and compressive strength at high temperature. Equipment for measuring wear due to contact between parts is usually evaluated at room temperature, and equipment for measuring wear at high temperature is rare. There is a problem that the evaluation by corrosion is also performed separately by flowing the corrosive gas using a high temperature electric furnace. High-temperature and corrosive environments can act simultaneously on thermal plants, gas turbine systems, and chemical reactors, and large thermal shocks can act simultaneously by sudden cooling.

In this context, damage refers to deformation, dislocation, microcrack, crack, wear scar, etc. occurring in the material of the part and how much it is subjected to high temperature, thermal shock, and corrosion. While the occurrence of the material deteriorates the life of the component material, it can be said that it is difficult because there is no patent on the accurate statistical processing and the device for evaluating the degree of damage and the method for evaluating the property therefrom.

In order to apply contact loads at high temperatures, an accurate load-carrying device is required, and the indenter under load must not be degraded by high temperatures. In addition, even after sudden cooling to room temperature after exposure to a high temperature environment, no significant damage to the refractory material or heating element of the electric furnace should be applied. In addition, it is difficult to be able to accurately measure the area (area, diameter) of the damage caused by the contact load. In addition, it should be accompanied by a method of observing and evaluating damage accurately, and it should be possible to accurately determine the type and extent of cracking.

The present invention is provided to solve the problems of the prior art as described above, may cause damage to the test piece by applying a contact load at a high temperature, withdraw the test piece from the high temperature to room temperature in a short time to apply a thermal shock, high temperature The purpose of the present invention is to devise and design a device capable of flowing corrosive gas in a state, and to provide a method of simultaneously or individually evaluating high temperature contact damage, thermal shock, and high temperature corrosion characteristics by using such equipment.

According to the design drawings of the device for achieving the above object, in the method for evaluating damage behavior by contact load at high temperature and evaluating thermal shock and high temperature corrosion characteristics, The part of the furnace consisting of refractory material for blocking heat, the part of the load cell for applying the load to the top of the electric furnace to adjust its size and measuring it, and the two different parts A part composed of a ceramic tube having excellent high temperature resistance for contacting with the contactor, an indenter for screwing and applying a load to the ceramic tube, and a part for supporting the test piece; A part consisting of a motor and a belt such that the support for supporting the specimen is drawn to room temperature by an automatic or manual method; It is designed and manufactured to be configured as a controller part to control the operation of the part, the temperature can be warmed and reduced from room temperature to 1500 ^o C, the pressure can be pressurized and reduced pressure from room temperature atmospheric pressure to 5000N by the control of the load cell In addition, an input device for allowing the hot corrosion gas to enter the inside of the electric furnace and an output part for allowing the gas to flow out of the corrosive gas are interconnected, so that the corrosive gas can flow uniformly at a constant flow rate. Provided is a method of designing and designing a device to prevent damage to a refractory or heating element due to thermal shock even when drawn out as a support for supporting a specimen at a temperature of 1500 ^o C.

In addition, by using such a high temperature plunger, it is possible to apply a force up to 5000 N while raising the temperature from room temperature to 1500 ^o C, to evaluate the damage caused by contact load at high temperature, and to measure the indentation stress by measuring the diameter damaged by the contact load ( The relationship between the applied load divided by the damage area and the indentation strain (divided by the radius of the indenter that damaged the damage) can be assessed and applied to the lower half of the furnace from a maximum temperature of 1500 ^o C to room temperature. Corresponding alumina parts can be lowered at the same time, so that thermal shock can be applied to evaluate the degree of damage due to thermal shock, and damage caused by chemical corrosion at high temperature by flowing corrosive gas (H ₂ , Na, K, Cl, etc.) into the electric furnace It is characterized by providing a method for evaluating the degree.

The method of evaluating damage due to contact load is a method of processing a male screw in the form of a screw on an alumina tube, a female thread of a cap and fastening, a method of bonding an indenter to a cement cement, and a high temperature. It is composed of a method of bonding a ball indenter such as alumina, silicon nitride, silicon carbide and the like having excellent heat resistance to an alumina tube. In addition, the alumina tube on the opposite side that is in contact with the spherical indenter consists of an alumina tube machined with a female threaded cap and a male thread for fastening the cap. An XY table is mounted underneath the lower alumina tube to move the specimen to indent the spot.

The method of evaluating the thermal shock consists of the alumina tube in which the cap with the test piece attached is screwed together with the electric motor connected to the belt so that the entire alumina tube with the test piece attached to the lower part of the electric furnace is pulled out by the force of the motor. . At this time, the vertical movement of the alumina tube is configured to be automatically made by a timer.

The method for evaluating high temperature corrosion is designed to allow the gas to flow in and out of the electric furnace, so that the gas flows in and out through it, and the flow meter is installed so that a certain amount of gas flows.

As described in detail above, by designing, fabricating and evaluating a high temperature pluripotent group capable of evaluating damage caused by contact load at high temperature, thermal shock and high temperature corrosion, the contact load at high temperature It can be applied to cause damage to the specimen, draw out the specimen from high temperature to room temperature in a short time and apply thermal shock, devise and design a device that can flow corrosive gas in high temperature state, and utilize such equipment It is advantageous to provide a method for independently or simultaneously evaluating high temperature contact damage, thermal shock, and high temperature corrosion characteristics.

Although the technical idea of the method for evaluating various characteristics at high temperature of the test piece using the high temperature pluripotent machine of the present invention has been described together with the accompanying drawings, this is illustrative of the best embodiment of the present invention, but the ceramic or the specific high temperature. The present invention is not limited to the conditions and the specific bending strength test method. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

In the following, a preferred embodiment of the method for evaluating damage behavior due to high temperature contact load according to the present invention will be described in detail.

According to a preferred embodiment of the present invention, a silicon nitride ceramic powder, which is a main raw material, and a mixture mixed with other additives are sintered by atmospheric pressure sintering at the same time as the nitriding reaction to prepare a test piece, and a contact load is applied by applying a load using spherical pressure particles at a high temperature. The present invention relates to a method for evaluating damage behavior due to contact load.

In the following, the manufacturing process of the silicon nitride test piece manufactured by the atmospheric pressure sintering method simultaneously with the nitriding reaction will be described in detail.

To the silicon nitride ceramic powder, which is the main component of the test piece raw material, sintering aids such as alumina, yttria and silicon powder are added. At this time, the sintering aid is added to increase the bonding force between the silicon nitride ceramic powder particles to increase the volume shrinkage at the time of sintering, and the total amount of such sintering aid is added in an amount of 1.0 to 15.0 wt% based on the silicon nitride ceramic powder. do.

CarboxyMethyl Cellulose (CMC), which is an organic binder, is added to the mixed silicon nitride ceramic powder and the sintering aid as a molding aid. The carboxymethyl cellulose added at this time is added and mixed 1.0 to 5.0wt% with respect to the mass of the silicon nitride ceramic powder. Then, these raw materials are placed in a polyethylene container and dry mixed in a vibration pot mill for 1 hour to achieve uniform mixing.

Meanwhile, separately from the solid mixture of the silicon nitride ceramic powder, the sintering aid and the molding aid, water is put together in a kneader and mixed evenly for 30 to 60 minutes to form a liquid mixture. At this time, the mass ratio of the liquid mixture is mixed in a ratio of 5.0-15.0 wt% of water with respect to the mass of the silicon nitride ceramic powder.

The solid mixture and the liquid mixture formed as described above are mixed again and aged at room temperature for 24 hours. After charging the matured mixture in the BN crucible, the silicon powder is filled. The filled crucible is placed in a vacuum heat treatment furnace and heated to a temperature of 1250-1450 ^o C. At this time, the atmosphere is maintained with nitrogen.

Meanwhile, the reason for maintaining the atmosphere as nitrogen in the above process is that the charged silicon and the nitrogen maintaining the atmosphere are converted into silicon nitride by a chemical reaction within a given temperature range. If the temperature is lower than 1250 ^o C, the silicon does not melt and no chemical reaction occurs. If the temperature is higher than the temperature of 1450 ^o C, the chemical reaction occurs excessively, so that a dense sintered body is not obtained.

The reactant, which has undergone nitrification, is heated up to 1750 ^~ 1820 ^o C in an electric furnace to keep it at high temperature for 1 ~ 3 hours, and to be made into a completely compact sintered body without surface pores for constant roll cooling. do.

After removing the densified specimen from the electric furnace and removing the excess silicon coagulant on the outside, the surface is polished and machined like a mirror using diamond.

In the following, a method of evaluating damage behavior of silicon nitride specimens prepared by atmospheric sintering at the same time as the nitriding reaction due to contact load at high temperature will be described.

In the drawings, Figure 1 is a photograph showing a schematic diagram of the high-temperature plurier designed and manufactured in the present invention, Figure 2 is a contact damage occurred in the silicon nitride test piece evaluated in accordance with one of the various conditions and the load and damage applied at this time The graph shows the indentation stress and strain from the radius of the indenter.

The silicon nitride test piece prepared as shown in FIG. 1 slots the top of the cap and fixes the test piece. The cap on which the specimen is mounted is screwed into the lower alumina tube. In addition, as a method for fixing the test piece, a method in which a cement having a predetermined thickness is adhered to the lower part of the test piece by bonding with ceramic cement and pressing for more than 24 hours by a clamp is also used.

Meanwhile, the alumina, silicon nitride, and silicon carbide ceramic balls are fixed to the cap in the same manner as above, and then fastened by screws to the upper alumina tube in the same manner.

The lower alumina tube is moved upwards by a motor connected by a belt to contact the spherical pressure particles mounted on the upper alumina cap. At this time, a heat resistant window is installed in the central part of the electric furnace to check the contact.

After contacting the specimen with the ceramic spherical indenter, pressure is applied using a load gauge mounted on the alumina tube equipped with the spherical indenter. When a certain pressure is applied, the pressure stops automatically.

After removing the load applied to the test specimens contacted at a constant pressure in a high temperature state by using a load cell, the electric furnace is cooled at a constant speed, and the cooled test specimens are cooled down to near room temperature by pulling down the lower alumina tube by a motor. The drawn specimen is analyzed by an optical microscope or an electron microscope to observe and analyze the degree of damage.

Examples were given to various methods evaluated using the high temperature pluripot designed and manufactured in the present invention shown in FIG. 1 to separate Examples 1 to 7 as shown in Table 1.

Example 1 relates to the damage evaluation caused by applying a load of 100 kgf at a temperature of 700 ^° C. in the method for evaluating damage behavior by contact load at a high temperature as described above. Shown in Evaluation is performed by the method shown in FIG. 3 as a method for evaluating the strength reduction of the test piece due to damage. The damage site of the test piece manufactured according to the embodiment is positioned below the strength measurement, and then the strength reduction rate is evaluated by evaluating the strength by the bending strength test. On the other hand, the results of analyzing the damage before the strength degradation due to contact damage is shown in Table 2. This method obtains the data by measuring the indentation stress divided by the area of the damage contacted as in Example 1 and the indentation strain by dividing the radius of the damage by the radius of the indenter. According to Table 2, the indentation stress and the indentation strain generally increase with increasing load, and the indentation stress increases with increasing indentation strain. On the other hand, the linear part of the indentation stress-indentation strain curve corresponds to the modulus of elasticity before yield failure occurs and the elastic modulus of the specimen can be measured.

Example 2 shows the results of evaluating the strength decrease after the evaluation by the high temperature thermal shock test using the high temperature plurier presented in the present invention. In this thermal shock, after heating the test specimen in the electric furnace to 700 ^o C, withdraw the lower alumina tube at room temperature within 1 minute, apply thermal shock and maintain it for 1 minute, then raise the alumina tube to the electric furnace for 1 minute. The cycle of maintaining the cycle is repeated several tens to thousands of times. After thermal shock, the upper surface of the test piece is placed between the lower spans of the strength test jig as shown in FIG. 3 to measure the strength.

Example 3 relates to a result of measuring the strength after placing the exposed surface in the lower span of the strength test jig of FIG. 3 after exposing the corrosive gas at a high temperature of 700 ^° C for a predetermined time. Corrosive gas is a gas containing Na, K, H, Ar, H ₂ flows, and measure the strength degradation of the test piece worn by corrosion.

Examples 4 to 6 are Examples 4, wherein the high-temperature corrosion test and the high-temperature thermal shock test were simultaneously performed using the high-temperature plural machine designed and manufactured according to the present invention. It consists of Example 6 which performed the high temperature corrosion test and the thermal shock test simultaneously, and relates to the result of evaluating the case where a high temperature, a load, a corrosion environment, and a thermal shock environment act simultaneously.

TABLE 1

TABLE 2

As shown in the results of Table 1 and Table 2, the high temperature pluripotency which can be evaluated under high temperature, load, corrosion environment and thermal shock environment according to the present invention not only evaluates each evaluation method simultaneously but also It is a distinctive invention that can be evaluated in one way to consider the impact. In addition, stress-strain behavior, which is one of the typical methods of evaluating mechanical behavior, can be obtained at high temperature and local damage in that indentation stress-indentation strain behavior can be obtained under compressive stress, unlike stress-strain at existing room temperature. It is an invention that can be evaluated from.

1 is a view showing a drawing of a high-temperature pluripot designed and manufactured according to the present invention,

FIG. 2 is a photograph showing a high temperature contact damage of a ceramic test piece evaluated according to one condition of various embodiments of the present invention (a), and a graph (b) showing the indentation stress-strain curve due to contact damage.

Figure 3 is a schematic diagram showing the strength measurement method for evaluating the strength degradation of the test piece evaluated by the high temperature universal machine.

Claims (9)

In the method of manufacturing a high temperature pluripot capable of measuring the high temperature contact damage, thermal shock, and high temperature corrosion characteristics, respectively or simultaneously, Constructing a furnace comprising a heating element for maintaining a high temperature and a refractory material for blocking heat to the outside; Constructing a load cell for applying a load to the upper portion of the electric furnace for adjusting the load and for adjusting and measuring the size thereof; Constructing a high temperature resistant ceramic tube supporting the two different parts in contact; And Comprising an indenter for applying a screw to the ceramic tube and applying a load and a support for supporting a test piece; Damage due to contact load at high temperatures, thermal shock and corrosion characteristics evaluation method characterized in that consisting of. In the manufacturing method using a high temperature pluripot manufactured by claim 1, Processing the external thread in the form of a screw on the alumina tube, and processing the cap with the internal thread to fasten it; Adhering the indenter to the cap with ceramic cement; And Bonding a ball indenter of at least one of alumina, silicon nitride, and silicon carbide having excellent heat resistance at a high temperature to an alumina tube; It consists of The cap on which the test piece is attached to the opposite alumina tube in contact with the spherical indenter is machined with a female thread, and consists of an alumina tube processed in the form of a male thread to fasten the cap, and after the indentation is applied to one point of the test piece, A method for evaluating damage characteristics due to damage due to contact load, thermal shock and high temperature corrosion at a high temperature, characterized in that an XY table capable of moving the specimen to indent at a point is mounted under the lower alumina tube. The method according to claim 1 or 2, Method for evaluating damage characteristics due to contact load at high temperature, thermal shock and high temperature corrosion, It is possible to apply the force up to 5000N while raising the temperature from normal temperature to 1500 ^o C, and to evaluate the damage caused by contact load at high temperature, and to evaluate the relationship between indentation stress and indentation strain by measuring the diameter damaged by the contact load. The parts corresponding to the lower half of the electric furnace from the temperature of 1500 ^o C to the room temperature can be simultaneously lowered, so that the thermal shock is applied to evaluate the degree of damage due to the thermal shock, and the corrosive gas is flowed into the electric furnace at high temperature. A method for evaluating damage characteristics due to contact load damage, thermal shock and high temperature corrosion at a high temperature, wherein the damage due to chemical corrosion can be evaluated to provide a method for evaluating the above tests individually or simultaneously. The method of claim 3, wherein The indentation stress is calculated by dividing the applied load by the damage area, and the indentation strain is calculated by dividing by the radius of the indenter that applied the radius of the damage, and is characterized by damage due to contact load, thermal shock and high temperature corrosion at high temperatures. Assessment Methods. The method of claim 3, wherein The corrosive gas is at least one of H ₂ , Na, K, Cl, Ar, damage due to contact load at high temperatures, thermal shock and damage characteristics evaluation by high temperature corrosion. Means composed of a motor, a belt and an alumina tube such that the support for supporting the test piece is drawn out to room temperature by an automatic or manual method; A controller for controlling each part to operate; A temperature controller capable of warming and reducing temperature from room temperature to 1500 ^o C; A load cell capable of pressurizing and depressurizing from room temperature atmospheric pressure to 5000N by control of the controller; An input device for allowing the hot corrosion gas to enter the interior of the electric furnace; Means for allowing the output gas to flow outside of the corrosive gas so that the corrosive gas can flow uniformly at a constant flow rate; Means for preventing damage to the fireproof material or heating element due to thermal shock even when drawing out as a support for supporting the specimen at a temperature of 1500 ^o C, Damage due to contact load at high temperatures, thermal shock and damage characteristics evaluation apparatus due to high temperature corrosion, characterized in that consisting of. The method of claim 6, Method for evaluating damage characteristics due to contact load at high temperature, thermal shock and high temperature corrosion, It is possible to apply the force up to 5000N while raising the temperature from normal temperature to 1500 ^o C, and to evaluate the damage caused by contact load at high temperature, and to evaluate the relationship between indentation stress and indentation strain by measuring the diameter damaged by the contact load. The parts corresponding to the lower half of the electric furnace from the temperature of 1500 ^o C to the room temperature can be lowered simultaneously, so that the thermal shock is applied to evaluate the degree of damage due to the thermal shock, and the corrosive gas is flowed into the electric furnace at high temperature. A method for evaluating damage characteristics due to contact load damage, thermal shock and high temperature corrosion at a high temperature, wherein the damage due to chemical corrosion can be evaluated to provide a method for evaluating the above tests individually or simultaneously. The method of claim 7, wherein The indentation stress is calculated by dividing the applied load by the damage area, and the indentation strain is calculated by dividing by the radius of the indenter that applied the radius of the damage, and is characterized by damage due to contact load, thermal shock and high temperature corrosion at high temperatures. Assessment Methods. The method of claim 7, wherein The corrosive gas is at least one of H ₂ , Na, K, Cl, Ar, damage due to contact load at high temperatures, thermal shock and damage characteristics evaluation by high temperature corrosion.

Images