RU2570117C1 - Unit for high temperature erosion testing - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: unit contains rack, secured on the foundation, bedplate installed on rack, camera and abrasive silo located on the bedplate, abrasive feed channel connected with silo, and air feed channel, they are inputs to the mixer, output from mixer is nozzle for air-abrasive mixture feed, it as the sample holder is located in the chamber. The unit additionally contains heater of the air-abrasive mixture secured on the mixer, sample heater secured on holder, branch pipe installed in the chamber through the thread hole in side surface of its casing, to fix the nozzle in chamber and distance to work surface of the test sample in the holder, flange installed on the chamber base using thread connections to fix the holder with test sample in chamber at angle to the nozzle axis.

EFFECT: expansion of functional abilities of the unit, and increased authenticity of tests.

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Description

The technical solution relates to test equipment and can be used to test alloys, coatings, and other materials operating under conditions of high-temperature erosion, characteristic of the tubes of furnace screens of boilers of thermal power plants.

A known installation for testing materials for gas abrasion wear [1], which implements mechanical acceleration of abrasive particles using centrifugal forces realized when the rotor rotates by an electric motor, due to which it is possible to control the feed rate of the abrasive particles. In this case, the samples are fixed symmetrically relative to the axis of the rotor in the holder, providing the ability to change the angle of attack of the abrasive. The disadvantage of the installation is the heterogeneity of the jet of abrasive over the cross section, which reduces the reliability of the results when testing coatings [2], in addition, there is no possibility of testing at high temperatures.

The technical solution, expanding the functionality of the installation [1] and providing the ability to test coatings for high-temperature gas abrasion wear [3], involves the placement of rotating samples in an electric furnace filled with suspended particles of abrasive. The disadvantages of the technical solution are the inability to control the speed of collision of particles with the sample and the angle of attack of the abrasive, which reduces the reliability of the results when testing coatings.

The installation [4] was selected as a prototype, in which the abrasive is accelerated by compressed air, which makes it possible to control the feed rate of the abrasive particles. The installation includes a chamber, an abrasive hopper, an abrasive supply path, an air supply path, a mixer, an air-abrasive mixture nozzle, and a sample holder. In contrast to the installation for testing for high temperature erosion [5], the nozzle for supplying an air-abrasive mixture is placed in an electric furnace. Due to the presence of the nozzle, the heterogeneity of the abrasive jet over the cross section is eliminated. The heating temperature of the test sample, fixed in the holder, is set in contact with air heated in an electric furnace, after which an abrasive is fed through the nozzle.

The disadvantages of the prototype include: the use of one heater (electric furnace) for the joint control of the heating temperature of the air-abrasive mixture and the test sample, which does not reflect the working conditions during high-temperature erosion of a wide range of parts, for example, in the electric power industry of boiler furnace screen tubes and reduces the reliability of test results for high temperature erosion; Rigid design of the sample holder, which allows testing only at two angles of attack of the abrasive (20 and 90 °) and at a fixed distance from the nozzle to the test sample (10 mm).

The objective of the technical solution is to expand the functionality of the installation and increase the reliability of the tests.

The problem is solved in that in the installation for testing high-temperature erosion, comprising a rack fixed in the foundation, a bed mounted on a rack, a chamber and an abrasive hopper located on the bed, an abrasive supply path connected to the hopper, and an air supply path serving entrances to the mixer, the exit from the mixer is an air-abrasive mixture supply nozzle, which, like the sample holder, is located in a chamber, characterized in that the air-abrasive mixture heater is additionally introduced; mounted on the mixer, and a sample heater mounted on the holder, a nozzle installed in the chamber through a threaded hole on the side surface of its body, for fixing the nozzle in the chamber and the distance to the working surface of the test sample in the holder, a flange mounted on the base of the chamber using threaded connections, for fixing the holder with the test sample in the chamber at an angle to the axis of the nozzle.

In FIG. 1 shows a diagram of an installation for testing high-temperature erosion, which includes a chamber 1, an abrasive hopper 2, an abrasive supply path 3, an air supply path 4, a mixer 5, an air-abrasive mixture supply nozzle 6, a sample holder 7, heaters 8 and 9 , fixing flange 10, fixing pipe 11, bed 12, stand 13.

Installation works as follows. The sample is fixed in the holder 7, which is placed in the chamber 1 and fixed, at a certain angle, by the flange 10. After that, the nozzle for feeding the air-abrasive mixture 6 is fixed in the pipe 11, thus, the distance from the nozzle to the working surface of the test sample and the angle of attack between the working surface of the sample in the holder and the axis of the nozzle. When compressed air is supplied along the path 4, the abrasive material from the hopper 2 enters the supply path of the abrasive 3 to the mixer 5 by injection. After which air is mixed with the abrasive and an air-abrasive mixture is formed. The mixture of air and abrasive is heated using heater 8, after which it exits through nozzle 6. After the interaction of the air-abrasive mixture with the test sample, the abrasive is poured into the hopper, injected into the abrasive supply path 3, so the abrasive cycle is closed in the laboratory setup presented. Exhaust air is removed by exhaust through the top of the unit. The sample is heated using the heater 9 by means of heat transfer from the holder 7. After completion of the tests, the sample is removed from the holder, it is cleaned from abrasive particles and weighed. The amount of wear is judged by the value of the difference in mass of the sample before and after the test.

Changing the angle of attack between the working surface of the sample in the holder 7 and the axis of the nozzle 6 in the range of 30-90 ° occurs due to the fixing flange 10 mounted on the camera 1, which allows you to position the holder with the sample fixed in it relative to the axis of the nozzle and expand the installation functionality. The indicated angles of attack are characteristic in tests for gas-abrasive wear and erosion of alloys and coatings. Thus, hardened steels wear out most intensively at an angle of attack of 60 °, and hard coatings - at an angle of attack of 90 °, and when the angle of attack changes from 60 ° to 30 °, the wear rate of coatings decreases faster than that of hardened steel. The discovered patterns are related to the fact that the hardness of the coatings under study is higher than that of hardened steel. Therefore, when testing with large angles of attack, to exhaust the ductility and create a riveted layer that can break, that is, to implement the main wear mechanism under these test conditions, harder materials, such as coatings, need less time than steel. At small angles of attack, when the micro-cutting mechanism is the main wear factor, coatings may turn out to be more resistant than steel [2].

The change in the distance from the nozzle to the working surface of the test sample in the holder 7 in the range of 10-50 mm occurs due to the fixation of the nozzle for supplying the air-abrasive mixture 6 with a fixing pipe 11 mounted on the chamber 1, which allows to expand the installation functionality. The distance interval of 10-50 mm is selected from the following considerations. At a distance of less than 10 mm, the abrasive particles do not have time to accelerate to the maximum speed required by the test conditions (76 m / s), and above 50 mm the particle speed decreases below the minimum required by the test conditions (38 m / s) [1].

The heating temperatures of the air-abrasive mixture and the test sample are changed separately using two separate heaters 8 and 9, which reflects the operating conditions for high-temperature erosion of a wide range of parts, for example, in the electric power industry of steam generator pipes, and allows to increase the reliability of the results of tests for high-temperature erosion.

Literature

1. GOST 23.201-78. Mechanical tests. Ensuring wear resistance of products.

2. L.I. Tushinsky, A.V. Plokhov, A.O. Tokarev. IN AND. Sindeev. Methods of research materials. - M .: Mir, 2004 .-- 384 p.

3. N. Pokhmurska, B. Wielage, T. Grund, M. Student and Y. Sirak. Arc sprayed coatings obtained from iron based cored wires under high temperature abrasive wear conditions. International Thermal Spray Conference Exposition ITSC 2008: book of abstract. Singapore: 2008. P.326-329.

4. S. Dallaire, H. Levert, and J.-G. Legoux. Erosion Resistance of Arc-Sprayed Coatings to Iron Ore at 25 and 315 ° C. Journal of Thermal Spray Technology, Vol. 10 (2), 2001. P.337-350.

5. DIN 50332-1989. Solid particle erosion test; basic rules.

Claims (1)

Installation for testing high-temperature erosion, comprising a stand fixed in the foundation, a stand mounted on a stand, a chamber and an abrasive hopper located on the bed, an abrasive supply path connected to the hopper, and an air supply path serving as inputs to the mixer, exit from the mixer is a nozzle for supplying an air-abrasive mixture, which, like the sample holder, is located in the chamber, characterized in that the heater of the air-abrasive mixture mounted on the mixer is additionally introduced, the sample heater a nozzle mounted on the holder, installed in the chamber through a threaded hole on the side surface of its housing, for fixing the nozzle in the chamber and the distance to the working surface of the test sample in the holder, a flange mounted on the base of the camera with threaded connections, for fixing the holder with the test sample in the chamber at an angle to the axis of the nozzle.