RU2733520C1 - Method and device for making articles from powders by layer-by-layer selective growing - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to production of an item by layer selective growing from powder. Proposed device comprises hopper with powder, working chamber with substrate for growing the product and laser to selectively scan powder layer. Substrate is provided with an oscillating system configured to operate in resonance mode, which includes an ultrasonic emitter mounted by means of a concentrator for amplification of oscillations on the substrate. Height of ultrasonic radiator, concentrator and substrate is multiple of half-wave at preset frequency of ultrasonic vibrations. Method of product manufacturing by layer-by-layer selective growing out of powder includes action on grown on article substrate ultrasonic oscillations by means of oscillating system with frequency of ultrasonic vibrations of 16–80 kHz and amplitude of 5–70 mcm.

EFFECT: reduction of defect formation in articles due to reduction of residual stresses and improvement of quality of fusion or sintering of powder particles, acceleration of diffusion processes in article and higher physical and mechanical, technological and operational properties of produced articles.

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Description

The technical field to which the invention relates

The invention relates to the manufacture of a three-dimensional product by selectively melting a powder in the form of successively applied layers of one or different powders.

State of the art

From the prior art [patent RU 2401180 C2, publication date: 10.10.2010] is known a method for producing gradient materials from powders, which includes sequential application of layers of powder from different materials, selective sintering of a given area, application of a new layer and its sintering. The device for implementing the known method contains a working chamber with an entrance window, a laser, a working hopper with a piston, a feeding hopper, a carriage for filling and placing the powder. In this case, the device for filling and laying is additionally equipped with a mechanism for cleaning and rolling in the powder.

The disadvantage of this method is the formation of defects in the product after fusion or sintering due to the occurrence of residual stresses arising as a result of uneven cooling and phase transformations of the material, going with volumetric changes, high requirements for powders in their shape and dispersion, the complexity of the process, the formation of defects in products after their fusion due to the non-uniform density of the powder and the formation of a step at the boundary of the resulting product, since the height of the compacted layer is different within the boundaries of the product and outside it.

The closest analogue of the present invention (prototype) is a method of selective laser growing of parts from metal powders, which includes sequential application of layers of powder of a given thickness, their alignment by means of a knife or roller, selective fusion or laser beam sintering of a given area, applying a new layer and sintering it [ Grigoryants A.G. and other Laser additive technologies in mechanical engineering / Textbook. - M .: publishing house of MSTU im. N.E. Bauman, 2018 .-- 278 p., P. 65]. The device for implementing this method consists of a hopper with powder, a working chamber with a substrate, a leveling knife or roller, and a laser. After each layer is melted, the substrate of the powder hopper rises, the substrate of the working chamber is lowered, a new layer of powder is applied and leveled, and the powder is fused or laser-sintered to obtain a finished product.

The disadvantage of the prototype is the formation of residual thermal and deformation stresses caused by thermal processes during heating and cooling of the layers of the resulting product, which lead to plastic deformation of the product (change in its shape) and the formation of cracks, non-equilibrium structure, porosity, warpage, delamination after fusion or sintering [Grigoryants A.G. and other Laser additive technologies in mechanical engineering / Textbook. - M .: publishing house of MSTU im. N.E. Bauman, 2018 .-- 278 p., P. 81]. Therefore, to remove residual stresses, obtain an equilibrium structure, increase the viscosity and plasticity of the material after growing the products, it is necessary to carry out additional heat treatment of the resulting products. However, such heat treatment complicates the technological process, but does not solve all the problems that arise and is not applicable for all materials [Grigoryants A.G. and other Laser additive technologies in mechanical engineering / Textbook. - M .: publishing house of MSTU im. N.E. Bauman, 2018 .-- 278 p., P. 81-83].

Disclosure of the essence of the invention

The technical problem of the present invention was to eliminate the disadvantages of the known technical solutions, including the prototype.

The technical result of the proposed invention is to reduce defect formation in products by reducing residual stresses and improving the quality of fusion or sintering of powder particles, accelerating diffusion processes in the product and increasing the physical, mechanical, technological and operational properties of the resulting products.

The technical problem is solved and the technical result is achieved by the fact that in the proposed method of manufacturing products from powders by layer-by-layer selective growing, including the sequential deposition of powder layers, their leveling by means of a knife or roller and selective fusion, in the process of layer-by-layer selective growing, the product is exposed to ultrasonic vibrations.

In a preferred embodiment of the proposed method, the vibration frequency is in the range of 16-80 kHz, and the vibration amplitude is 5-70 μm, depending on the material and particle size of the powder, the size of the product. The choice of vibration frequency is determined by the fact that vibrations in the ultrasonic range have a number of advantages in comparison with vibrations of the audible range: the possibility of obtaining directional radiation and focusing vibrations, as a result of which the intensity of ultrasonic vibrations in certain zones of exposure increases. The amplitude of vibrations depends on the type of material being processed, the shape and size of the resulting product.

In another embodiment of the method, the product to be grown and the powder are simultaneously exposed to ultrasonic vibrations.

To implement the proposed method, a device is also proposed containing a hopper with a powder, a working chamber with a substrate, a leveling knife or roller for leveling the powder, a laser, and at least one ultrasonic emitter is installed on the substrate of the working chamber.

In one embodiment of the proposed device, the substrate of the working chamber corresponds in shape and size to the base of the product to be grown.

In another embodiment of the device, the vibrational system, including an ultrasonic emitter, a concentrator, a substrate, has a size that is a multiple of a half-wave of ultrasonic vibrations.

The introduction of ultrasound into the body of the resulting product and into the selective fusion zone allows obtaining the following effects:

1. When ultrasound passes through the product, diffusion processes, processes of thermal and chemical-thermal treatment, natural and artificial aging are accelerated, the physical-mechanical, technological and operational properties of products are improved [Khorbenko I.T. Ultrasound in mechanical engineering / Edition 2. - M .: Mechanical Engineering, 1974 .-- 280 p., P. 259-261].

2. When the processes of laser welding and ultrasonic processing of the material are combined, the formation of pores in the welded seams is suppressed, the metal structure is more uniform, the melt degassing occurs, and the mechanical characteristics of the product increase. At the same time, an increase in the frequency of ultrasonic vibrations leads to a decrease in porosity in the seam [Gorunov A.I. et al. Investigation of the influence of ultrasonic effects on laser welding of stainless steel / Materials of the V International Conference "Additive Technologies: Present and Future", March 22, 2019, p. 74-79].

3. The effect of ultrasound on the powder in the process of growing the product contributes to a denser and more uniform packing of powder particles (it starts to "flow", as it were), increasing its density, which also reduces defect formation in the products, improves the quality of fusion or sintering of powder particles.

Brief Description of Drawings

The essence of the proposed method and device for its implementation is illustrated by drawings, which should not limit the scope of claims of the claimed technical solution, since they are only illustrative materials of a particular case of its implementation.

FIG. 1 shows a diagram of an installation for implementing the proposed method for manufacturing products from powder by layer-by-layer selective growth.

FIG. 2 shows a variant of the design of the installation for the simultaneous action of ultrasound on the grown product and powder.

FIG. 3 shows a general view of a substrate with a disk radiator.

Implementation of the invention

The proposed method includes sequential deposition of layers of powder from one or different materials and selective sintering or fusion of a given area in the plane of each layer. The device for implementing the method consists of a working chamber and a powder feed hopper. The powder is melted by laser radiation scanning its surface. The powder is transferred from the feed hopper to the working chamber and leveled in the working chamber with a knife or roller.

The installation diagram for implementing the proposed method for manufacturing products from powder by layer-by-layer selective growth consists of a hopper 1 for feeding powder 2, a working chamber 3, in which the product is formed 4. The powder is melted by laser radiation 5, scanning the surface of the treatment zone. After each melting of the layer, the substrate 6 of the working chamber 3 is lowered by an amount slightly greater than the thickness of the model layer to level the process of shrinkage of the powder during fusion or sintering. After that, the substrate 7 of the hopper 1 rises. The powder 2 is transferred and leveled with a knife or roller 8 over the surface of the processing zone 9 and is selectively fused or sintered. This operation is repeated until the finished product is received.

To reduce defect formation in products by reducing residual stresses, improving the quality of fusion or sintering of powder particles, suppressing the formation of pores, accelerating diffusion processes, heat treatment processes, to increase the physicomechanical, technological and operational properties of the resulting products in the process of layer-by-layer selective growth on the product act with ultrasonic vibrations. For this, at least one ultrasonic emitter 10 (magnetostrictive, piezoceramic or other transducer) is installed on the substrate 6 of the working chamber 3. Substrate 6, in shape and size corresponding to the base of the grown product, is part of an oscillatory system, which includes: an ultrasonic (magnetostrictive or piezoceramic) emitter (transducer), a concentrator (an intermediate element between the ultrasonic emitter and a knife or roller, which is installed if necessary fluctuations); emitter - substrate 6. Substrate 6 is in this case the emitting element of the system. The vibration frequency is preferably in the range from 16 to 80 kHz, and the vibration amplitude is preferably 5 to 70 µm, depending on the material and particle size of the powder, the size of the product. Concentrators are made of structural medium-carbon steels, titanium, aluminum and other alloys. The substrate 6 rests on the base of the substrate 11 and moves with it. To reduce the energy loss of ultrasonic vibrations, an insulating pad 12 is located between the substrate 6 and the base of the substrate 11.

When ultrasonic vibrations are simultaneously applied to the grown product and the powder, the substrate 6 in shape and size corresponds to the base of the substrate 12.

All these elements represent a system coordinated with each other in terms of acoustic, mechanical and design parameters. The system should operate in a resonant mode, i.e., it is preferable that the height of the emitter, concentrator and substrate be a multiple of the half-wave L = λ / 2 at the selected frequency. Wavelength λ = C / ƒ, where: С - wave propagation speed, ƒ - vibration frequency. When a product is grown, it is part of the oscillatory system. In the process of growing the product, its height increases, and the resonance mode can be violated. Therefore, the ultrasonic generator must have a resonance mode adjustment system. When adjusting the resonance mode (changing the vibration frequency), the wavelength changes, so all parts of the grown product will periodically be located between the antinode of displacements (at this point, the maximum vibration amplitude and minimum voltage are observed) and the displacement node (in this place, the maximum voltage and minimum vibration amplitude are observed ). This contributes to the production of a product with desired and uniform properties throughout the volume.

After preparation of the powder layer, a protective gas (nitrogen, argon) is supplied to the working chamber. Next, the layer of powder is subjected to fusion or sintering with a laser beam in accordance with the software of the fusion or sintering mode. With the design of the next layers, the cycle of operations is repeated until the entire product is manufactured. Ultrasonic vibrations are turned on after obtaining a certain height from the product, which depends on the material of the product and its dimensions.

After that, the finished product is subjected to cooling, powder cleaning and removal from the working chamber.

Execution example

As an emitter when installing it on a substrate, you can use the oscillatory systems UZAGS-0.3 / 22-O, UZAGS-0.4 / 22-O with an oscillation frequency of 22 ± 1.65 kHz and a substrate 6 in the form of a disk emitter (Fig. 3). Emitter power 300 W, 400 W. A concentrator 13 is installed between the emitter 10 and the substrate (disk emitter) 6 to amplify the oscillations. To connect the emitter 10, the concentrator 13 and the substrate 6 to each other, a threaded connection is used with a stud, which allows, if necessary, to disconnect and connect them. Substrate material, concentrator - titanium alloy.

Claims (2)

1. A device for manufacturing an article by layer-by-layer selective growing from powder, containing a hopper with powder, a working chamber with a substrate for growing the article and a laser made with the possibility of selective scanning of the powder layer, characterized in that the substrate is equipped with an oscillating system capable of operating in a resonant mode comprising an ultrasonic emitter installed by means of a concentrator to amplify vibrations on the substrate, the height of the ultrasonic emitter, the concentrator and the substrate being a multiple of a half-wave at a given frequency of ultrasonic vibrations. 2. A method of manufacturing an article by layer-by-layer selective growing from powder in a device for manufacturing an article by layer-by-layer selective growing according to claim 1, including sequential deposition of powder layers and selective scanning with a laser, while the article grown on the substrate is affected by ultrasonic vibrations by means of an oscillatory system with a frequency of ultrasonic vibrations 16-80 kHz and an amplitude of 5-70 microns.

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