METHOD FOR ADDITIVE MANUFACTURING OF THREE-DIMENSIONAL OBJECTS

Abstract

A method for additive manufacturing three-dimensional objects from metals and their alloys in the process of melting subsequent layers of the alloying material in the form of a powder with a laser beam or an electron beam with the manufacturing of the object itself and support structures which are subsequently removed from the object itself through chemical etching of the material, characterized in that the support structures have a permeability higher than 10.sup.-12 m.sup.2, measured in the direction parallel to the plane defined by the layer of the deposited powder, with the thickness of the support structure wall is no larger than 1 mm, and the etching liquid contains at least one component which on its own causes a passive layer to form on the surface of the processed material and the etching liquid is subject to ultrasounds with an intensity larger than the cavitation threshold in the medium.

Claims

1. A method for additive manufacturing of three-dimensional objects from metals and their alloys in a process of melting subsequent layers of an alloying material in the form of a powder with a laser beam or an electron beam to obtain said object being manufactured with support structures which are afterwards detached from said object by chemical etching of the material in the etching liquid, characterized in that the support structures have a permeability higher than 10.sup.-12 m.sup.2, as measured in at least one direction parallel to a plane defined by a layer of the deposited powder, and thickness of the support structure wall equal or lower than 1 mm, and the etching liquid contains at least one compound having by itself an effect of forming a passive layer on the surface of the processed material and the etching liquid is subjected to ultrasounds with an intensity larger than cavitation threshold of a medium.

2. The method according to claim 1, characterized in that the support structures are soaked in a solution containing one of the components of the etching liquid and then moved to a container containing the second component of the etching liquid.

3. The method according to claim 2, characterized in that the first solution includes an aqueous solution of metal fluorides, chlorides, or bromides, and the second solution contains an oxidizing acid.

4. The method according to claim 3, characterized in that the after soaking the support structures with the first solution, the solvent is evaporated.

5. The method according to claim 2, characterized in that after the support structures are soaked with the first component, the surplus of the first component is removed by rinsing in a cleaning solution.

6. The method according to claim 1, characterized in that the ultrasound intensity is higher than 5 W/m.sup.2.

7. The method according to claim 1, characterized. in that the area of contact of the support structure with said object has a porosity larger than said object.

8. The method according to the claim 1, characterized in that the distance between support structure walls is larger than 100 μm.

9. The method according to claim 1, characterized in that the produced support structures directly supporting said object have height of maximally 20 mm and remaining height is filled by forming support structures having greater thickness and lower porosity.

10. The method according to claim 1, characterized in that the manufactured object and the support structures are made from metallic materials, such as: technical grade titanium, austenitic steel, high-temperature nickel alloys, AlSil2 silumin.

11. The method according to claim 1, characterized in that the manufactured object and the support structures are made from alloys containing at least 80 atom percent of titanium and the etching reagent is a solution of HF and HNO.sub.3 in a concentration from 1% to 4% and 2% to 7%, respectively.

12. The method according to claim 1, characterized in that said object and the support structures are made from alloys containing at least 80 atom percent nickel and iron, and the etching reagent is a solution of HF and HNO.sub.3 in a concentration from 4% to 20% and 1% to 4%, respectively and preferably, said object and the support structures are made from alloys containing at least 80 atom percent aluminum and the etching reagent is a solution of NaOH and KOH in a concentration from 10% to 50% in a temperature of 50-80° C.

13. A method for additive manufacturing three-dimensional objects from metals and their alloys in the process of melting subsequent layers of the alloying material in a form of a powder with a laser beam or an electron beam to manufacture said object with support structures which are subsequently removed from said object through chemical etching of the material, characterized in that the support structures have a permeability higher than 10.sup.-12 m.sup.2, measured in the direction parallel to the plane defined by the layer of the deposited powder, with the thickness of the support structure wall lower or equal 1 mm, and the etching takes place in at least two solutions, with the first solution causing a passive layer to develop on the material surface, and the second solution causing selective dissolution of the passive layer.

14. The method according to claim 13, characterized in that the material subjected to etching is an AlSil2 aluminum alloy and the first solution contains an oxidizing acid and the passive layer consists of oxides or hydroxides of the material subjected to etching and the second solution contains a non-oxidizing acid.

15. The method according to claim 14, characterized in that the first solution includes an alkaline solution of metal fluorides, chlorides, or bromides, and the second solution contains hydrochloric acid.

16. The method according to claim 13, characterized in that the first solution contains metal ions with an electrochemical potential larger in relation to the base material than the corrosion potential of the material etched in the solution, and the second solution contains.

17. The method according to the claim 16, characterized in that the etched material is steel 1.2709 and the first solution contains copper (II) salt ions, and the second solution contains ammonium ions.

18. The method according to the claim 13, characterized in that the processing is conducted alternatively in the first and the second solution.

19. The method according to the claim 13, characterized in that the etched components are rinsed in one or more neutralizing solutions between processing in different etching solutions.

Description

Example 1

[0039] Two materials were used in the experiments: technical grade titanium (TiCP) and silumin AlSil2. From both of these materials an object in the shape of a cube with a side length of 20 mm was produced, placed with a wall parallel to the plane determined by the deposited powder layer, on supports with a height of 10 mm. The support structure was composed of parallel plates with a width determined by a single passing of a laser beam with 50 W power at 400 mm/s speed for TiCP and 60 W and 600 mm/s for AlSil2, i.e., 90 and 120 micrometers, respectively. For the support structures, a TiCP alloy with a porosity of 11% and a AlSil2 alloy with a porosity of 9% were used. The distance between plates was set at 500 μm. The support structure permeability was calculated to be 5*10.sup.-7 m.sup.2. The prepared AlSil2 alloy model along with the support structures was initially cleaned in an ultrasonic bath in distilled water, and was subsequently placed in a reaction chamber, where an etching agent in the form of 10% NaOH solution was added. The etching was carried out in a temperature of 80° C., in the minimal time required for the model to be separated, which was 8 minutes with ultrasound intensity of 0.5 W/cm.sup.2 at a 20 kHz frequency. The loss of mass in the manufactured object was 0.21 g.

[0040] The finished TiCP alloy model along with the support structures was initially cleaned in an ultrasonic bath in distilled water, and was subsequently placed in a reaction chamber, where an etching agent in the form of 1.3% HF and 9% HNO.sub.3 solution was added. The etching was carried out in a temperature of 80° C., in the minimal time required for the model to be separated, which was 6 minutes with ultrasound intensity of 0.3 W/cm.sup.2 at a frequency of 20 kHz. The loss of mass in the manufactured object was 0.51 g.

[0041] For the sake of comparison, the same cube models were produced from the same materials, with the difference being that the support structures were placed in the standard way, i.e., as walls crossing each other, maintaining identical distances between the walls, i.e. 500 μm. For the TiCP alloy model, the minimal etching time was 20 minutes, with a 4.2 g loss in weight of the manufactured object, and for the AlSil2 alloy object the minimal etching time was 96 minutes, with a 2.61 g loss in weight of the manufactured object. Both experiments were conducted with ultrasound intensity of 0.5 W/cm.sup.2 at a frequency of 20 kHz.

Example 2

[0042] In another example of the realization, a cube with a side of 20 mm was produced from TiCP. Support structures in the shape of poles with a diameter of 500 μm and porosity of 12% were produced with the parameters of 40 W and 500 mm/s. The distance between the supports was 200 μm and the calculated permeability was 10.sup.-9 m.sup.2. What is important, the low permeability value was a consequence of the deposition of the sintered powder between the support structures. Next, the object was rinsed with distilled water for 10 min, and subsequently twice for 3 min in a solution of 1.3% HF and 9% HNO.sub.3 with ultrasound intensity of 0.5 W/cm.sup.2 at frequency of 20 kHz, which allowed for the support structures to be completely etched.

Example 3

[0043] In another example of the realization, a cube with a side of 20 mm was produced from TiCP. Support structures in the shape of poles with a diameter of 500 μm and porosity of 0.5% were produced with the parameters of 50 W and 500 mm/s. The distance between the supports was 200 μm and the calculated permeability was 10.sup.-9 m.sup.2. What is important, the low permeability value was a consequence of the deposition of the sintered powder between the support structures. Next, the object was rinsed with distilled water for 10 min, and subsequently four times for 3 min in a solution of 1.3% HF and 9% HNO.sub.3 with ultrasound intensity of 0.5 W/cm.sup.2 with a frequency of 20 kHz, which allowed for the support structures to be completely etched.

Example 4

[0044] Another example of the realization of the invention is a component of a heat engine from AlSil2. Support structures in the shape of poles with a diameter of 500 μm and porosity of 12% were produced with the parameters of 40 W and 500 mm/s. The distance between the supports was 2000 μm and the calculated permeability was 10.sup.-5 m.sup.2. Next, the object was rinsed with distilled water for 10 min, and subsequently for 3 min each in a solution of 10% KClO.sub.4 and 3 min in a 5% HCl solution. The last two steps were repeated five times with ultrasound intensity of 0.5 W/cm.sup.2 at a frequency of 20 kHz.

Example 5

[0045] Another example of the realization of the invention is a component of a heat engine from TiCP. Support structures in the shape of poles with a diameter of 500 μm and porosity of 2% were produced with the parameters of 60 W and 500 mm/s. The distance between the supports was 1000 μm and the calculated permeability was 10.sup.-5 m.sup.2. Next, the object was rinsed with distilled water for 10 min, and subsequently for 10 min in a solution of 10% NaF, then it was dried for 4 hours in a temperature of 373 K. Then, the object was rinsed for 1 min in distilled water and moved to a solution of 9% HNO.sub.3, where it was rinsed for 6 minutes with ultrasound intensity of 0.5 W/cm.sup.2 at a frequency of 20 kHz.

Example 6

[0046] Another example of the realization of the invention is a cube with a side of 20 mm, made of 1.2709 steel. Support structures in the shape of cylinders with a diameter of 2 mm, wall thickness of 100 μm and porosity of 2% were produced with the parameters of 30 W and 125 mm/s. The distance between the supports was 1000 μm and the calculated permeability was 2*10.sup.-7 m.sup.2. Next, the object was rinsed with distilled water for 10 min, and subsequently for 12 min in a solution of 5% CuSO.sub.4 and 2 min in 5% NH4Cl and 5% HCl. The last two steps were repeated ten times with ultrasound intensity of 0.5 W/cm.sup.2 at the 20 kHz frequency.