Method of spray forming an object

Abstract

The invention relates to a method of forming a 3-dimensional solid object, comprising the steps: a) cold spraying one or more metallic powder to form a solid three dimensional item; b) thermally sintering the item such that a portion of the sprayed powder liquefies and reduces spaces between, and/or non-adhesion of, one or more solid portions of the item; and c) causing or allowing the portion of the sprayed powder that liquefied on heating, to become solid.

Claims

1. A method of forming a 3-dimensional solid object, comprising the steps: a) cold spraying one or more metallic powder to form a solid three dimensional item, the one or more metallic powder comprising a blend of a at least a majority powder being a main matrix forming powder and at least a minority powder being a sintering powder; b) thermally sintering the item such that a portion of the sprayed powder liquefies and reduces spaces between, and/or non-adhesion of, one or more solid portions of the item; wherein: i. the item is heated and held at one or more temperature below a lowest melting temperature of an alloy formed by the matrix powder and the sintering; and then ii. is heated to a temperature above said lowest melting temperature; and c) causing or allowing the portion of the sprayed powder that liquefied on heating, to become solid.

2. A method according to claim 1, wherein the majority powder and/or the minority powder each comprise alloy.

3. A method according to claim 1, wherein a shape of the item when formed is substantially determined by the matrix forming powder.

4. A method according to claim 1, wherein it is substantially only the sintering powder that liquefies at step b).

5. A method according to claim 1, wherein the matrix forming powder has an additional metallic content of: a) less than 3% by weight, b) less than 2.2% by weight, or c) less than 1.5%, by weight.

6. A method according to claim 1, wherein at least majority or larger group of the matrix forming powder comprises primarily one or more of aluminium, copper, nickel, iron and/ or a 6000 series aluminium alloy.

7. A method according to claim 1, wherein the matrix forming powder comprises a ceramic substance.

8. A method according to claim 1, wherein the sintering at step b) is by a sintering powder comprising a majority of one or more of aluminium, copper, nickel, tin and zinc.

9. A method according to claim 1, wherein the sintering at step b) is by a sintering powder that is: a) less than 15% by weight of the sprayed powder; b) less than 10% by weight of the sprayed powder; or c) less than 5% by weight of the sprayed powder.

10. A method according to claim 1, wherein the combination of the matrix forming powder and the sintering powder has a minority of elements that provide sintering at step b), the minority of elements comprising one or more of magnesium, silicon, carbon, nickel, copper, zinc, tin, aluminium, lithium, chrome, iron and manganese.

11. A method according to claim 1, wherein: a) the cold sprayed one or more metallic powder, as the sprayed powder comprises aluminium, Al—Si—Mg and copper, and, at claim 1 step b), the item is: i. held at 524-610° C. for at least 1 to 7 hours; and subsequently ii. held at to 470-550° C.; and then iii. cooled such that alloying elements are in a saturated solid solution; or b) the sprayed powder comprises copper, and aluminium, up to about 15% by weight aluminium, and, at claim 1 step b), the item is held at 850-1000° C. for at least 8 to 16 hours; or c) the sprayed powder comprises copper and aluminium, up to about 15% by weight aluminium, with up to 4% iron, and up to 3% nickel or silicon; or d) the sprayed powder comprises copper and zinc, up to about 15% by weight zinc, and, at claim 1 step b), the item is held at 850-950° C. for at least 8-14 hours; or e) the sprayed powder comprises copper and tin, up to about 10% by weight tin, and, at claim 1 step b), the item is held at 850-950° C. for at least 8 to 14 hours; or f) the sprayed powder comprises iron and copper, up to about 5% by weight copper, and, at claim 1 step b), the item is held at 1,096-1,200° C. for at least 8-14 hours; or g) the sprayed powder comprises iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is held at 1,455-1,490° C. for at least 8-14 hours; or h) the sprayed powder comprises nickel and copper, up to about 15% by weight copper, and, at claim 1 step b), the item is held at 1,100-1,300° C. for at least 8-14 hours.

12. A method according to claim 1, wherein: a) the cold sprayed one or more metallic powder, as the sprayed powder comprises aluminium, Al—Si—Mg and copper and, at claim 1 step b), the item is: i. held at 450-525° C. for 15-300 minutes; and subsequently ii. held at 524-610° C., for least 1-7 hours; and subsequently iii. held at to 470-550° C.; and then iv. cooled such that alloying elements are in a saturated solid solution; or b) the sprayed powder comprises copper and aluminium, up to about 15% by weight aluminium, and, at claim 1 step b), the item is: i. held at 325-400° C. for at least 4-18 hours; and subsequently ii. held at 850-1000° C. for at least 8-16 hours; or c) the sprayed powder comprises copper and zinc, up to about 15% by weight zinc, and, at claim 1 step b), the item is: i. held at 320- 400° C. for at least 1 to 8 hours; and subsequently ii. held at 850-950° C. for at least 8 to 14 hours; or d) the sprayed powder comprises copper and tin, up to about 10% by weight tin, and, at claim 1 step b), the item is: i. held at 200-230° C. for at least 1-8 hours; and subsequently ii. held at 850-950° C. for at least 8 to 14 hours; or e) the sprayed powder comprises copper and tin, up to about 10% by weight tin, and, at claim 1 step b), the item is: i. held at 231-400° C. for at least 5-25 minutes; and subsequently ii. held at to 850-950° C. for at least 8-14 hours; or f) the sprayed powder comprises iron and copper, up to about 5% by weight copper, and, at claim 1 step b), the item is: i. held at 800-1,096° C. for at least 1-8 hours; and subsequently ii. held at 1,096-1,200° C. for at least 8-14 hours; or g) the sprayed powder comprises iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is held at 1,455-1,490° C. for at least 8-14 hours; or h) the sprayed powder comprises iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is: i. held at 1,000-1,455° C. for at least 1-8 hours; and subsequently ii. held at 1,455-1,490° C. for at least 8-14 hours; or i) the sprayed powder comprises iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is: i. held at 1,455-1,490° C. for at least 8-14 hours; and subsequently ii. held at to 750-900° C., and subsequently iii. cooled to produce a martensitic structure; or j) the sprayed powder comprises nickel and copper, up to about 15% by weight copper, and, at claim 1 step b), the item is: i. held at 900-1,100° C. for at least 1-8 hours; and subsequently ii. held at 1,100-1,300° C. for at least 8-14 hours.

13. A method according to claim 1, wherein: a) the cold sprayed one or more metallic powder, as the sprayed powder comprises copper and aluminium, up to about 15% by weight aluminium, and, at claim 1 step b), the item is: i. held at 325-400° C. for at least 4-18 hours; and subsequently ii. held at 850-1,000° C. for at least 8-16 hours; and subsequently iii. held at to 800-1000° C.; and then iv. cooled such that alloying elements are in a saturated solid solution; or b) the sprayed powder comprises copper and zinc, up to about 15% by weight zinc, and, at claim 1 step b), the item is: i. held at 320-400° C. for at least 1 to 8 hours; and subsequently ii. held at 420-550° C. for at least 5-25 minutes; and subsequently iii. held at 850-950° C. for at least 8 to 14 hours; or c) the sprayed powder comprises iron and copper, up to about 5% by weight copper, and, at claim 1 step b), the item is: i. held at 1,096-1,200° C., for at least 8-14 hours; and subsequently ii. held at to 750-900° C., and subsequently iii. cooled to produce a martensitic structure.

14. A method according to claim 1, wherein: a) the cold sprayed one or more metallic powder, as the sprayed powder consists of Aluminium, Al—Si—Mg and copper, and, at claim 1 step b), the item is: i. held at 524-610° C. for at least 1 to 7 hours; and subsequently ii. held at to 470-550° C.; and then iii. cooled such that alloying elements are in a saturated solid solution; or b) the sprayed powder consists of Aluminium, Al—Si—Mg and copper and, at claim 1 step b), the item is: i. held at 450-525° C. for 15-300 minutes; and subsequently ii. held at 524-610° C., for least 1-7 hours; and subsequently iii. held at to 470-550° C.; and then iv. cooled such that alloying elements are in a saturated solid solution; or c) the sprayed powder consists of copper, and aluminium, up to about 15% by weight aluminium, and, at claim 1 step b), the item is held at 850-1000° C. for at least 8 to 16 hours; or d) the sprayed powder consists of copper and aluminium, up to about 15% by weight aluminium, and, at claim 1 step b), the item is: i. held at 325-400° C. for at least 4-18 hours; and subsequently ii. held at 850-1000° C. for at least 8-16 hours; or e) the sprayed powder consists of copper and aluminium, up to about 15% by weight aluminium, and, at claim 1 step b), the item is: i. held at 325-400° C. for at least 4-18 hours; and subsequently ii. held at 850-1,000° C. for at least 8-16 hours; and subsequently iii. held at to 800-1000° C.; and then iv. cooled such that alloying elements are in a saturated solid solution; or f) the sprayed powder consists of copper and aluminium, up to about 15% by weight aluminium, with up to 4% iron, and up to 3% nickel or silicon; or g) the sprayed powder consists of copper and zinc, up to about 15% by weight zinc, and, at claim 1 step b), the item is held at 850-950° C. for at least 8-14 hours; or h) the sprayed powder consists of copper and zinc, up to about 15% by weight zinc, and, at claim 1 step b), the item is: i. held at 320-400° C. for at least 1 to 8 hours; and subsequently ii. held at 850-950° C. for at least 8 to 14 hours; or i) the sprayed powder consists of copper and zinc, up to about 15% by weight zinc, and, at claim 1 step b), the item is: i. held at 320-400° C. for at least 1 to 8 hours; and subsequently ii. held at 420-550° C. for at least 5-25 minutes; and subsequently iii. held at 850-950° C. for at least 8 to 14 hours; or j) the sprayed powder consists of copper and tin, up to about 10% by weight tin, and, at claim 1 step b), the item is held at 850-950° C. for at least 8 to 14 hours; or k) the sprayed powder consists of copper and tin, up to about 10% by weight tin, and, at claim 1 step b), the item is: i. held at 200-230° C. for at least 1-8 hours; and subsequently ii. held at 850-950° C. for at least 8 to 14 hours; or l) the sprayed powder consists of copper and tin, up to about 10% by weight tin, and, at claim 1 step b), the item is: i. held at 231-400° C. for at least 5-25 minutes; and subsequently ii. held at to 850-950° C. for at least 8-14 hours; or m) the sprayed powder consists of iron and copper, up to about 5% by weight copper, and, at claim 1 step b), the item is held at 1,096-1,200° C. for at least 8-14 hours; or n) the sprayed powder consists of iron and copper, up to about 5% by weight copper, and, at claim 1 step b), the item is: i. held at 800-1,096° C. for at least 1-8 hours; and subsequently ii. held at 1,096-1,200° C. for at least 8-14 hours; or o) the sprayed powder consists of iron and copper, up to about 5% by weight copper, and, at claim 1 step b), the item is: i. held at 1,096-1,200° C., for at least 8-14 hours; and subsequently ii. held at to 750-900° C., and subsequently iii cooled to produce a martensitic structure; or p) the sprayed powder consists of iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is held at 1,455-1,490° C. for at least 8-14 hours; or q) the sprayed powder consists of iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is: i held at 1,000-1,455° C. for at least 1-8 hours; and subsequently ii. held at 1,455-1,490° C. for at least 8-14 hours; or r) the sprayed powder consists of iron and nickel, up to about 5% by weight nickel, and, at claim 1 step b), the item is: i. held at 1,455-1,490° C. for at least 8-14 hours; and subsequently ii. held at to 750-900° C., and subsequently iii. cooled to produce a martensitic structure; or s) the sprayed powder consists of nickel and copper, up to about 15% by weight copper, and, at claim 1 step b), the item is held at 1,100-1,300° C. for at least 8-14 hours; or t) the sprayed powder consists of nickel and copper, up to about 15% by weight copper, and, at claim 1 step b), the item is: i. held at 900-1,100° C. for at least 1-8 hours; and subsequently ii. held at 1,100-1,300° C. for at least 8-14 hours.

15. A method according to claim 1, wherein the cold sprayed one or more metallic powder, as the sprayed powder at claim 1 step a) consists of or comprises: a) spheroidal particles; and/or b) particles that are not irregular, spiky or rough; and/or c) particles, at least 90% of which are 15-80 μm in span; d) particles, at least 90% of which are 15-45 μm span.

16. A method according to claim 1, wherein the matrix forming powder has a hardness of less than 200 HV.

17. A method according to claim 1, wherein the matrix forming powder has a hardness of less than 150 HV.

18. A method according to claim 1, wherein the matrix forming powder has a hardness of less than 100 HV.

19. A method according to claim 1, wherein: a) a shape of the item when formed is substantially determined by the matrix forming powder; b) it is substantially only the sintering powder that liquefies at step b); c) matrix forming powder has an additional metallic content of: i. less than 3% by weight, ii. less than 2.2% by weight, or iii. less than 1.5%, by weight; d) at least most of the matrix forming powder comprises primarily one or more of aluminium, copper, nickel, iron and/or a 6000 series aluminium alloy; e) the sintering at step b) is by a sintering powder comprising a majority of one or more of aluminium, copper, nickel, tin and zinc; and f) the combination of the matrix forming powder and the sintering powder has a minority of elements that provide sintering at step b), the minority comprising one or more of magnesium, silicon, carbon, nickel, copper, zinc, tin, aluminium, lithium, chrome, iron and manganese.

20. A method according to claim 1, wherein: a) a shape of the item when formed is substantially determined by the matrix forming powder; b) it is substantially only the sintering powder that liquefies at step b); c) at least most of the matrix forming powder comprises primarily one or more of aluminium, copper, nickel, iron and/or a 6000 series aluminium alloy; d) the sintering at step b) is by a sintering powder comprising a majority of one or more of aluminium, copper, nickel, tin and zinc; and e) the combination of the matrix forming powder and the sintering powder has a minority of elements that provide sintering at step b), the minority comprising one or more of magnesium, silicon, carbon, nickel, copper, zinc, tin, aluminium, lithium, chrome, iron and manganese.

Description

IMAGES

(1) Some preferred embodiments of the invention will now be described by way of example and with reference to the accompanying images of which:

(2) FIG. 1 is a phase diagram for copper;

(3) FIG. 2 illustrates, photographically, a series of blocks prepared by cold spraying a blend of Al—Si10-Mg powder+3% Cu powder;

(4) FIG. 3 is a phase diagram for Al—Si10-Mg; and

(5) FIG. 4: illustrates, photographically, a further block prepared by cold spraying a blend Al—Si10-Mg+3% Cu.

DETAILED DESCRIPTION

(6) Various three dimensional objects were formed by cold spraying according to the details noted below.

EXAMPLE 1

(7) Cold Sprayed Aluminium Alloy 6061 Powder

(8) Aluminum Alloy 6061 is a commercially available product, for example as described at https://en.wikipedia.org/wiki/6061_aluminium_alloy.

(9) Aluminum Alloy 6061 is sometimes used as a solid “wrought” product having a density of about 2.7 g/cm.sup.3, a melting pint of approximately 580° C., a modulus of elasticity of about 70-80 GPa, a Poissons ratio of about 0.33, a thermal conductivity of about 173 W/m.Math.K and an electrical resistivity of about 3.7-4.0×10-6 Ω.Math.cm.

(10) Aluminum Alloy 6061 is available in Australia as a powder from Ecka Granules Germany, a subsidiary of Kymera International (https://www.kymerainternational.com/), and has a composition substantially as shown in the table below.

(11) TABLE-US-00001 Component Amount (% wt) Aluminium Balance Magnesium 0.8-1.2 Silicon 0.4-0.8 Iron Max. 0.7 Copper 0.15-0.40 Zinc Max. 0.25 Titanium Max. 0.15 Manganese Max. 0.15 Chromium 0.04-0.35 Others 0.05

(12) Cold sprayed powdered Aluminum Alloy 6061 is often substandard to the wrought version in terms of the tensile strength of the finished product. This is believed to be attributable to incomplete bonding of particles within a layer, and/or between sprayed layers, in the microstructure of a cold sprayed item.

(13) Aluminum Alloy 6061 powder was cold sprayed using compressed air at 30 bar and 500° C. to produce a series of standard tensile test bars. These were heat treated as follows: Anneal: 575° C.×4 hr+Air Cool Solutionise: 530° C.×1 hr+Water Quench Age: 200° C.×1 hr

(14) The bars were then subjected to break and elongation testing, with average results as shown in the table below. The table also provides a comparison with wrought Aluminum Alloy 6061.

(15) TABLE-US-00002 Cold Sprayed Aluminum Wrought Aluminum Alloy 6061 powder Alloy 6061 Break Stress, MPa 147 310 Elongation at Break, % 0.33 8

(16) As indicated in the table, it is possible to effectively cold spray items from Aluminum Alloy 6061 powder. These deposit and build effectively, but the particles involved do not bond quite as well and give the same strength as for wrought aluminum.

EXAMPLE 2

(17) Cold Sprayed Aluminum Alloy 6061 Powder+4% Cu Powder

(18) Copper particles were found to deposit well when cold sprayed. However pure copper appears to have no or insufficient ability for thermal hardening and so is generally believed to be of limited use for structural applications. It was an unlikely candidate for cold spraying items that need to have significant strength.

(19) However the inventors have discovered that Copper powder can be combined with Aluminum Alloy 6061 powder and cold sprayed to good effect. When sprayed in mixture with Aluminum Alloy 6061 powder, the copper powder was found to form a liquid phase above 548° C. in the resulting 3D product (as illustrated in FIG. 1). It was surprisingly discovered that that the copper gave rise to a finished item significantly harder than for Aluminum Alloy 6061 powder alone. The copper was found to have moderate diffusivity in the aluminum, making the copper able to form a ready sintering liquid phase and less likely to simply dissolve into the aluminum matrix.

(20) A blend of Aluminum Alloy 6061 powder and 4% Cu powder, by weight, was cold sprayed using compressed air at 30 bar and 500° C. to form a series of standard tensile test bars. These were heat treated as follows: Sintering: 610° C.×3 hr+Furnace cool Solutionising: 505° C.×1 hr+Water Quench Aging: 160° C.×1 hr

(21) The resulting material was tensile tested and was found to have significant strength. This is illustrated in the table below, including a comparison to the Example 1 results.

(22) TABLE-US-00003 Cold Sprayed Aluminum Alloy 6061 powder Cold Sprayed Wrought with 4% Cu Aluminum Alloy Aluminum powder 6061 powder Alloy 6061 Break Stress, MPa 293 147 310 Elongation at Break, % 1.5 0.33 8

(23) The Example 2 item, ie with copper in the blend, was significantly stronger than the Example 1 item, and also compared very well against the wrought item. In short, the addition of the copper powder, together with the ‘after-spraying heat treatment’, gave remarkably improved a breaking stress and elongation parameters.

EXAMPLE 3

(24) Porosity of 6061+4% Cu Varies Depending on Heat Treatment

(25) Referring to FIG. 2 a series of blocks were formed by cold spraying a blend of Aluminum Alloy 6061 powder and 4% Cu powder, by weight, at 30 bar and 500° C. These were then heat treated as follows:

(26) TABLE-US-00004 Sintering Treatments for FIG. 2 Sample Number Heat Treatment Details A No heat treatment B 555° C. × 6 hr + (FC + 530° C.) × 1 hr + WQ C 570° C. × 6 hr + (FC + 530° C.) × 1 hr + WQ D 605° C. × 1 hr + FC + 530° C. × 1 hr + WQ FC = Furnace Cool WQ = Water Quench.

(27) As shown in FIG. 2, Sample A did not show any visible porosity. However Samples B and C displayed substantial gross porosity during the heat treatment, lowering their density and making the finished item unsuitable for many mechanical applications. In surprising contrast, Sample D displayed no visible porosity, making it a candidate for mechanical applications.

EXAMPLE 4

(28) Al—Si10-Mg+3% Cu Fails to Cold Spray

(29) A common powdery alloy for 3D printing (eg Selective Laser Melting) is Al-10Si—Mg. A typical composition for this is illustrated below.

(30) TABLE-US-00005 Component Amount (% wt) Aluminium Balance Magnesium 0.25-0.35 Silicon 9.5-10.5 Iron Max. 0.7 Copper 0.05 max Zinc Max. 0.25 Titanium Max. 0.15 Manganese Max. 0.15 Chromium 0.04-0.35 Others 0.05

(31) Al-10Si—Mg alloy is designed to fuse and was thought to be suitable for liquid phase sintering in a cold spray context. As illustrated in FIG. 3, it has a large two-phase region (eg a large temperature zone in which it can be solid or liquid) suitable for liquid formation. Furthermore, it is able to be hardened in a similar manner to sprayed Aluminum Alloy 6061. The addition of Cu was thought to be sufficient for lowering the temperature at which sintering liquid is first present, to as little as 524° C. (Fig X). It was thought that this would promote the action of liquid phase sintering, as well as augmenting hardening response on final heat treatment as described above.

(32) To test the above, a block of material was cold sprayed using a blend of Al—Si10-Mg powder and 3% Cu powder, by weight. The powder was applied using air at 30 bar and 500° C. However the block did not form correctly, as shown at FIG. 4. This was because the Al—Si10-Mg was found to have a low deposition efficiency in that only approximately 15% of the material sprayed was successfully incorporated into the block, the rest rebounding. This surprisingly poor result was attributed to an excessive proportion of hard silicon in the aluminum powder.

EXAMPLE 5

(33) 6061+5% Al-10Si—Mg+1% Cu with Pre-Sintering Treatment Gives Surprising Performance

(34) The 6061 alloy powder of Examples 1 and 2 was blended with 5% Al-10Si—Mg and 1% Cu, then cold sprayed. The sprayed part was then subjected to an unusual heat treatment, including a “pre-sintering” treatment, as follows: Pre-Sintering: 500 C×20 min Sintering: 595 C×4 hr Solutionise: 530 C×1 hr+Water Quench

(35) The samples were then aged 150 C×2.5 hr

(36) This returned the remarkable result tabulated below:

(37) TABLE-US-00006 Previous Examples Cold Sprayed Aluminum Alloy 6061 Cold Sprayed powder with Aluminum Wrought 4% Cu Alloy 6061 Aluminum Example 5 powder powder Alloy 6061 Break Stress, 298 293 147 310 MPa Elongation at 7.5 1.5 0.33 8 Break, %

EXAMPLE 6

(38) Application of Pre-Sintering to Aluminium Bronze

(39) Without wishing to be bound by theory, it is believed that pre-sintering treatment in Example 5 may improve the penetration of liquid along poorly-bonded interfaces, and act to reduce porosity. This effect may be generalized to various alloy systems, for example, aluminium bronze.

(40) A pure copper powder was blended with the 10% 6061 powder of Examples 1 and 2. This was cold sprayed into parts and then heat treated in 2 ways, then tested, as per the table below. Additionally, a fully alloyed aluminium bronze powder (ie without a sintering agent) was cold sprayed and tested for comparison. The blended powder with 2 pre-sintering steps performed remarkably well.

(41) TABLE-US-00007 Composition of Elongation, Powder Heat Treatment UTS, MPa % Blend of Powders 400 C. × 5 hr, then 280 4.4 Cu + 10% 6061 950 C. × 12 hr Blend of Powders 325 C. × 16 hr, then 312 5.3 Cu + 10% 6061 555 C. × 0.5 hr, then 950 C. × 16 hr Aluminium Bronze 850 C. × 10 hr + WQ 180 0.3 alloy (Cu—10% Al)

(42) In terms of disclosure, this document hereby envisages and discloses each item, step or other feature mentioned herein in combination with one or more of any of the other items, steps or other features disclosed herein, in each case regardless of whether such combination is claimed.

(43) While some preferred forms of the invention have been described by way of example it should be understood that modifications and improvements can occur without departing from the invention or the following claims.