RU2310551C2 - Method for restoring machine parts surface flaws - Google Patents

Abstract

FIELD: metallurgy, namely methods for repairing machine parts surface flaws, possibly restoration of machine parts of high alloy refractory steels and alloys having operation flaws such as air holes, dents, local worn zones of rubbing surfaces.

SUBSTANCE: method comprises steps of filling dressed flaw sites with melt powder material containing solder and filler at deposition of said material by means of argon micro-plasma; sealing applied material by depositing onto it refractory material layer with thickness 0.2 - 0.3 mm at temperature exceeding at least by 100°C melting temperature of filler; depositing aluminum oxide layer with thickness 0.1 - 02 mm as barrier layer preventing tinning of repaired part surface with solder; then performing high-temperature soldering in vacuum and also in gas-shield atmosphere; mechanically working part. Invention allows receive high quality soldered joints without changing shape of deposited material in all spatial positions of part during restoration at porosity of soldered joints no more than 1.5%.

EFFECT: possibility for receiving high quality soldered joints.

5 cl, 1 ex

Description

The invention relates to the field of repair of parts, in particular to methods of repair of parts from high alloy heat-resistant steels and alloys, and can find application in the aviation and shipbuilding industries, as well as in power engineering.

A known method for correcting surface defects on parts made of heat-resistant alloys such as gas turbine blades (US Patent No. 5735448, B23K 1/008, 228-119). The surface on which defects are found is cleaned and coated on it, containing: 2-6% volatile organic carrier; 20-60% of a water-based carrier; 3% fluxing agent containing a halide compound; 1-5% thickener, the rest is a metal aggregate, which is a two-component powder mixture. The first component of the mixture is a fine powder, the chemical composition of which corresponds to the chemical composition of the part. The second component contains a similar metal powder, as well as an additive that reduces the melting point. The first and second components are thoroughly mixed, as a result of which the total chemical composition of the mixture approximately corresponds to the chemical composition of the part. After coating, the part is heated to 524-552 ° C. Then, the component is continued to be heated to the melting temperature of the second component of the mixture, while the first component remains in the solid state. After that, the part is heated to 1193-1215 ° C, as a result of which the melting point depressant diffuses into the part and the first component, causing repeated isothermal solidification. After exposure, the part is cooled and subjected to minimal machining to the original size.

The disadvantages of this method: the inability to obtain high-quality soldered joints in any spatial position of the part; the soldering process is carried out only in vacuum.

The closest technical solution, selected as a prototype, is a method for repairing surface defects of gas-turbine engine products (RF Patent No. 2240214, В23Р 6/00). The method includes cleaning the repaired surface of the products, applying a filler in the form of a paste based on a metal powder with an organic binder, high-temperature vacuum soldering followed by homogenization of the product with a composite overlay coating and final machining of the products. Before applying the filler in the form of a paste, a flexible filler of nickel mesh with a sintered layer of granules made of heat-resistant nickel alloy is applied to the surface to be repaired. After applying the filler in the form of a paste, the fillers are sintered with the product in a vacuum and then applied to the filler layer of heat-resistant solder on a nickel basis. Granules sintered with a nickel mesh are placed in one layer and are uniform in size. The paste filler consists of a powder of heat-resistant nickel alloy having a particle size of 2.5-3 times smaller than the size of the granules sintered with a nickel mesh. High-temperature vacuum brazing is carried out according to the thermal vacuum treatment of the base material with the possibility of carrying out it simultaneously with the homogenization of the composite overlay coating.

This method does not allow to eliminate operational defects on repaired surfaces such as shells, nicks, local wear of rubbing surfaces, which during soldering can be located in vertical and ceiling positions, and also does not provide stable soldered joints with a continuity of ≤1.5%.

The problem to which the invention is directed was to obtain stable high-quality soldered joints in all spatial positions, not only in a vacuum, but also in a shielding gas medium with a continuity not exceeding ≤1.5%.

To solve the technical problem, we propose the following method for repairing surface defects of machine parts made of high alloy steels and alloys, including preparing the surface of the part, spraying powder materials using argon microplasma, followed by high-temperature soldering and machining. Spraying using argon microplasma consists in the following: defects on parts are filled with molten powder material consisting of solder and filler, which is protected from oxidation by atmospheric oxygen by an argon stream flowing out of the plasma torch nozzle; the applied material is sealed by spraying a heat-resistant VKNA material with a thickness of 0.2-0.3 mm with a temperature of ≥100 ° C higher than the melting temperature of the filler, and aluminum oxide 0.1- thick 0.2 mm. Soldering is carried out both in vacuum and in a shielding gas medium. The essence of the spraying of powder materials using argon microplasma is that the sprayed powder is introduced in the initial portion of the plasma arc at an angle to the plasma flow. In this case, heating and acceleration of the particles of the sprayed material occurs directly in the plasma arc, where the temperature reaches 8000-9000 ° C. This can significantly increase the efficiency of the spraying process. It should also be noted that the flow of sprayed particles has a small divergence angle (≈3-5 degrees) with an outlet nozzle-anode diameter of 2.0-3.0 mm, which allows dense local coatings to be applied, and the effect of heat flow on the part is negligible.

Argon-microplasma installation provides a stable process of applying powder materials. Particles of molten material in the form of fine droplets when applied to a defective surface of the part are deformed upon impact and the formation of porosity in the deposited material is almost completely eliminated. Filling the broken defects on the parts with molten material consisting of solder and filler provides a porosity of ≤1.5%. Reducing the fluidity of the solder, as well as increasing the strength of soldered joints, is achieved by adding a certain amount of filler to the solder. Work began with a solder ratio of 40% - filler 60%. With this ratio, partial leakage occurred during soldering of the deposited material from the broken defects. As the percentage of filler in the mixture (solder-filler) increased, the fluidity of the sprayed material decreased, and with the percentage of solder 20% - filler 80%, the fluidity of the sprayed mixture was practically absent, which makes it possible to obtain high-quality soldered joints in all spatial positions at high temperature soldering, this porosity in the deposited material is practically absent and does not exceed 1.5%. The data were obtained as a result of metallographic studies. The heat-resistant VKNA material applied by an argon-microplasma installation with a temperature of ≥100 ° C higher than the filler temperature creates a sufficiently strong and airtight skeleton on the outer surface of the deposited material (solder + filler), which prevents the solder from flowing out during soldering and allows to obtain high-quality soldered joints during soldering in protective gases. The absence of a tinned zone provides a barrier layer consisting of alumina; the outer surface of the material retains its original appearance with characteristic irregularities formed during plasma spraying.

Implementation example

This method was used to repair nozzle vanes of the first, second, and third stage of a gas turbine engine with operational surface defects: nicks, sinks, wear of rubbing surfaces, etc. The blades are made of alloys ZhS6U and ChS70. Mechanically, defective places were cut with the complete removal of defective areas. Cutting control was carried out by capillary defectoscopy. Then the blades were degreased. Spraying was carried out using an argon-microplasma unit such as UGNP. SPLIT defects on the blades filled with molten powder material consisting of a solder VI _p 50 and _p 36 EP filler at a percentage of brazing filler and 20% + 80%. Then, the VKNA heat-resistant material was sprayed with a thickness of 0.2-0.3 mm with a temperature of ≥100 ° C higher than the melting temperature of the filler to seal the deposited material. The heat-resistant material VKNA created a strong and airtight frame on the outer surface of the sawn material. As a barrier layer, excluding tinning by soldering the surface of the blade, aluminum oxide 0.1-0.2 mm thick was sprayed.

The assembled blades were subjected to high temperature soldering in vacuum according to the regime:

Temperature T _arr - 1190 ^{+ 10 °} С;

The exposure time is 10-15 minutes;

Medium rarefaction - (1-4) · 10 ^-4 mm Hg

Part of the blades with sprayed materials was subjected to high-temperature brazing in an Ar medium according to the regime:

Soldering temperature - 1200 ^{+ 10 °} С;

The exposure time is 15 min;

Protective environment

Ar with a flow rate of 1-2 l / min.

The quality control of soldered joints was carried out visually and using optical instruments with an increase of 4 times.

The blades were machined to the desired geometric dimensions. Sealed areas after machining were subjected to x-ray inspection and capillary method. Metallographic analysis showed that after soldering in the deposited material, the porosity does not exceed 1%, the structure of the material is fine-grained, and the size and shape of the deposited material are practically unchanged.

The repaired blades were deemed suitable for further use as part of the product.

Thus, the proposed method for repairing surface defects of machine parts provides a complete restoration of the structural dimensions of the parts, obtaining high-quality soldered joints in all spatial positions of the part, allows to obtain a significant economic effect in the repair of parts and increase their service life.

Claims (5)

1. A method of repairing surface defects of machine parts, including preparing the surface of the part, applying the material to the defective part of the surface, high-temperature soldering and machining, characterized in that the material used is a powder material consisting of solder and filler, and it is applied by sputtering with argon microplasma in in the form of molten powder material and seal the applied material by spraying a heat-resistant VKNA material with a temperature of ≥100 ° С higher than the melting temperature ator, and before high-temperature soldering to the surface component to be repaired is sprayed barrier layer of aluminum oxide to eliminate surface tinning solder. 2. The repair method according to claim 1, characterized in that the heat-resistant material VKNA is sprayed with a thickness of 0.2-0.3 mm. 3. The repair method according to claim 1, characterized in that the aluminum oxide is sprayed with a thickness of 0.1-0.2 mm 4. The repair method according to claim 1, characterized in that the high-temperature soldering is carried out in vacuum or in a protective gas medium. 5. The repair method according to claim 1, characterized in that for the implementation of high-temperature brazing in all spatial positions and to obtain soldered joints with porosities not exceeding ≤1.5%, without changing the shape of the deposited material, use a material consisting of 20% solder and 80% filler.