RU2593066C1 - Diffusion welding of ceramic-matrix composite with metals - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention can be used at connection of ceramic-matrix composite with metals. On element from ceramic-matrix composite activating intermediate layer is applied and elements are assembled with arrangement of interlayer between them. Activating layer used is nickel, silver, gold or copper and applied in form of galvanic coating with thickness 3-9 mcm on element of ceramic-matrix composite. At assembly of elements intermediate gasket with thickness of 0.05-0.1 mm made from nickel foil or porous tape of ultrafine powder of metal chosen from group: nickel, copper, silver, gold is arranged. Welding of produced assembly is performed at temperature of 1,050-1,100 °C, specific compression pressure of not more than 2.5 kg/mm², delay time of not less than 60 minutes, wherein heating rate is equal to cooling rate and does not exceed 50 °C/min.

EFFECT: method enables to obtain high-quality welded joint with required strength characteristics; plastic deformation of metal part is less than 5 %, its microstructure does not change, plastic deformation of part from ceramic-matrix composite is absent.

1 cl, 1 tbl, 4 ex

Description

The invention relates to welding, and in particular to methods of connecting parts from a ceramic composite to metals by diffusion welding, and can be used to weld parts operating in operating conditions with high quality requirements for welded joints.

The prototype of this invention is a method of diffusion welding of ceramics made of silicon nitride with steel (USSR author's certificate No. 1676772, class B23K 20/16, publ. 09/15/91), according to which a metallized layer based on molybdenum powder is preliminarily applied to the surface to be welded. Between the welded surfaces of the intermediate strip, steel and ceramic, layers of vanadium and copper, respectively, are located. The details are squeezed, heated and isothermal.

The disadvantage of this method is the low productivity of the process and the high complexity of manufacturing, the use of expensive and rare-earth metals molybdenum and vanadium, the formation in the connection zone of chemicals (solid solutions of molybdenum in vanadium and copper), significantly different from the base of the parts to be joined, which changes the physicomechanical properties welded products, i.e. strength characteristics of the weld, do not have a sufficient level.

A known method of connecting a heat-resistant alloy on a cobalt basis with ceramics based on silicon nitride (RF application No. 2433026, publ. 10.11.2011, IPC V23K 20/00 (2006.01)) using diffusion welding of a heat-resistant alloy on a cobalt basis with ceramic based silicon nitride using an intermediate material at a temperature of 900 ± 10 ° C, a pressure of 17 ± 1 MPa for 1800 ± 30 s, and a mechanical mixture of nickel, copper and cobalt, which contains 0.1 ... 0.3, is used as an intermediate material the weight. % Cu, 0.1 ... 0.3 weight. % Co, the rest is Ni.

The disadvantage of this method is the low productivity and high complexity of manufacturing, low strength characteristics, low diffusion permeability.

The problem to which the invention is directed is to develop a method for the diffusion welding of a ceramic composite with metals in vacuum, to eliminate the above disadvantages, to expand technical capabilities through the use of an intermediate transition layer, which has high mechanical properties and forms a durable and high-quality welded joint optimal selection of the welding mode. This allows:

- reduce the complexity of the welding process;

- eliminate significant changes in the structure of the metal material;

- provide the necessary strength of the connection;

- minimize the plastic deformation of the metal part and exclude it in the composite.

The specified technical result is achieved by the fact that the proposed method of diffusion welding of parts from a ceramic-ceramic composite with metals in vacuum allows applying a galvanic coating of nickel, silver, gold or copper to a thickness of 3-9 μm on the composite, and placing nickel foil between the galvanic layer and the metal surface or porous tape based on ultrafine powder of nickel, copper, silver or gold with a thickness of 0.05-0.1 mm The applied galvanic coating and the intermediate layer significantly reduce the value of residual stresses. In addition, the galvanic coating with the intermediate layer forms a solid solution, which provides a smooth, continuous change in the composition and properties in the weld zone, as well as the diffusion mobility of the elements, contributing to the formation of a strong connection. The specified intermediate layer of Nickel has high mechanical strength, and also contributes to its strong attachment to the composite due to the fact that during the action of pressure there is an interaction of nanodispersed nickel oxides with the composite.

The welding process includes the assembly of parts for welding, evacuation, heating to a welding temperature and holding in vacuum for a time, ensuring the passage of the diffusion process. Welding temperature 1000-1100 ° C. The speed of heating parts for welding should not exceed 50 deg / min, the specific compression pressure of not more than 2.5 kg / mm ² , the exposure time of 60 minutes Then the welding force is removed and cooled to room temperature, while the cooling rate should be equal to the heating rate, i.e. 50 deg / min.

The essence of the invention lies in the fact that the selected welding modes and the intermediate layer allow you to activate the diffusion mobility of the atoms of the materials and thereby ensure high mechanical properties of the weld. The applied pressure must be lower than the yield strength of the metal material being welded so that it does not cause its plastic deformation, therefore, does not change the initial microstructure, and also eliminates the need for laborious machining. The choice of temperature is due to the fact that when heated below 1000 ° C, diffusion mobility of atoms is not achieved and high strength of the weld is not ensured, and when heated above 1100 ° C, plastic deformation of parts more than 5% is formed and a sharp increase in metal grain is observed. The exposure time of 60 min ensures the complete passage of the diffusion exchange process between the electroplated layer, nickel foil or porous tape based on ultrafine powder and metal. When holding for less than 60 min, diffusion processes do not have time to provide a strong connection.

Example 1. A piece of a ceramic composite was welded with a steel part. The ceramic matrix composite is a TiNC bar with dimensions of 20 × 20 × 20 mm. The part is made of steel grade EP866, with a diameter of 20 mm, a height of 50 mm, a 6 mm thick nickel plating is applied to the composite. An intermediate gasket with a diameter of 20 mm and a thickness of 0.05 mm made of nickel is placed between the galvanized composite element and the steel element. Further, the steel part is joined with its end surface in the center of the composite part.

The elements to be connected were placed in a diffusion installation with a specific compression pressure of 2 kg / mm ² , holding time 60 min and heating rate not exceeding 50 ° C / min, welding was carried out at a temperature T = 1050 ° C, after which the compression pressure was removed and cooling was carried out to room temperature at a rate not exceeding 50 ° C / min.

Example 2. A piece of a ceramic composite was welded with a steel part. The ceramic matrix composite is a TiNC bar with dimensions of 20 × 20 × 20 mm. A part made of steel grade EP866, with a diameter of 20 mm, a height of 50 mm, a copper plating of 9 μm thickness is applied to the composite. An intermediate spacer of nickel foil or a porous tape of ultrafine nickel powder with a diameter of 20 mm and a thickness of 60 μm is placed between the galvanized composite element and the steel element. Further, the steel part is joined with its end surface in the center of the composite part.

The elements to be connected were placed in a diffusion installation with a specific compression pressure of 1.5 kg / mm ² , holding time of 100 min and heating rate not exceeding 50 ° C / min, welding was carried out at a temperature of T = 1000 ° C, after which the compression pressure was removed and carry out cooling to room temperature at a rate not exceeding 50 ° C / min.

Example 3. A part was made of a ceramic composite with a steel part. The ceramic matrix composite is a TiNC bar with dimensions of 20 × 20 × 20 mm. A part made of steel grade EP866, with a diameter of 20 mm, a height of 50 mm, a silver plating thickness of 5 μm is applied to the composite. An intermediate gasket with a diameter of 20 mm and a thickness of 0.1 mm of nickel is placed between the galvanized composite element and the steel element. Further, the steel part is joined with its end surface in the center of the composite part.

The elements to be connected were placed in a diffusion installation with a specific compression pressure of 2.5 kg / mm ² , holding time of 60 min and heating rate not exceeding 50 ° C / min, welding was carried out at a temperature of T = 1100 ° C, after which the compression pressure was removed and carry out cooling to room temperature at a rate not exceeding 50 ° C / min.

Example 4. A piece of a ceramic composite was welded with a steel part. The ceramic matrix composite is a TiNC bar with dimensions of 20 × 20 × 20 mm. A part made of steel grade EP866, with a diameter of 20 mm, a height of 50 mm, a galvanic coating of gold with a thickness of 3 μm is applied to the composite. An intermediate strip of nickel foil or a porous tape of ultrafine copper powder with a diameter of 20 mm and a thickness of 60 μm is placed between the galvanized composite element and the steel element. Further, the steel part is joined with its end surface in the center of the composite part.

The elements to be connected were placed in a diffusion unit with a specific compression pressure of 2 kg / mm ² , holding time 120 min and heating rate not exceeding 50 ° C / min, welding was carried out at a temperature T = 1020 ° C, after which the compression pressure was removed and cooling was carried out to room temperature at a rate not exceeding 50 ° C / min.

The test results of the mechanical properties of parts at a temperature of 20 ° C, according to standard test methods, are presented in the table.

Thus, the proposed method of diffusion welding of a ceramic composite with metals provides a solid connection, not less than 90% of the tensile strength in bending of the base material, which is much higher compared to the prototype and the analogue. As a result of using the proposed method, the range of application of welded joints from ceramic-ceramic composites is expanded and their resource is increased.

Claims (1)

The method of diffusion welding of elements from a ceramic composite and metal, including applying an activating intermediate layer to an element from a ceramic composite, assembling elements with spacers between them and welding the assembly at a temperature and compression pressure, characterized in that a metal selected from group, including nickel, copper, silver and gold, while it is applied in the form of a galvanic coating with a thickness of 3-9 microns on an element of a ceramic composite, when assembling using a 0.05-0.1 mm thick strip of nickel foil or a porous tape of ultrafine metal powder selected from the group consisting of nickel, copper, silver and gold is welded, and the assembly obtained is welded at a temperature of 1000-1100 ° C, specific pressure compression of not more than 2.5 kg / mm ² and the exposure time of at least 60 minutes, while the heating rate is equal to the cooling rate and does not exceed 50 ° C / min.