Porous Metal Coatings Using Shockwave Induced Spraying

Abstract

A new spray process allows for deposition below a critical velocity limit of cold spray, while providing adhesion. Post deposition heat treatment has shown excellent coating strength. A wide variety of materials can be deposited. The spray process is based on ShockWave Induced Spraying (SWIS) but with much slower spray jet projection velocities. High porosity, pore size control, and porosity control are demonstrated to be controllable. Preheating of feedstock and uniform temperature of the SWIS delivery allow for the deposition below critical velocity.

Claims

1. A method for producing a porous coating on a substrate; the method comprising: providing a particulate material having a given melting point and a given particle size distribution; providing a ShockWave Induced Spraying (SWIS) device comprising a tubular chamber with a generally uniform cross-sectional area having a spraying end and a gas inlet opposite the spraying end, and a gas supply fluidly connected to the gas inlet, where the gas supply contains a gas at a pressure higher than a pressure within the tubular chamber, the SWIS device comprising: a first controllable valve located between the gas supply and gas inlet for regulating a flow of gas into the tubular chamber from the gas inlet; a powder feeding system having an outlet operatively connected to the tubular chamber downstream of the gas inlet to feed the particulate material into the tubular chamber; and a heater for preheating the particulate material to a preheat temperature prior to delivery to the tubular chamber, maintaining the gas in the gas supply at a temperature lower than the melting point of the particulate material; directing the spraying end of the spraying device towards the substrate; feeding the particulate material within the tubular chamber in a controlled manner; generating a pressure wave traveling along the tubular chamber from the gas inlet to the spraying end by opening and closing the controlling valve, the pressure wave accelerating the particulate material longitudinally within the tubular chamber towards the spraying end; and projecting the particulate material through the spraying end onto the substrate at an average particle velocity to coat the substrate; wherein, an amplitude and a frequency of the pressure wave, the preheat temperature, a feeding rate of the particulate material, and the particle size distribution of the particulate material are chosen so that the average particle velocity allows a deposition of the particles while limiting a deformation of the particles to produce a porous coating on the substrate.

2. The method of claim 1 where the SWIS device further comprises a second controllable valve for regulating the feed of the particulate material into the tubular chamber.

3. The method of claim 1 further comprising heat treating the coating on the substrate after deposition, to improve interparticle metallurgical contact.

4. The method of claim 3 where after heat treatment the porous coating has a shear strength greater than 20 MPa, or a tensile strength greater than 20 MPa.

5. The method of claim 1 where the particulate material is preheated at a preheating temperature of between 50° C. to 1000° C. prior to delivery to the tubular chamber.

6. The method of claim 1 where the particulate material is preheated at a preheating temperature of 0.15 to 0.7 times a melting point of the particulate material measured in ° C. prior to delivery to the tubular chamber.

7. The method of claim 6 where the preheating temperature is 0.3 to 0.6 times a melting point of the particulate material measured in ° C.

8. The method of claim 1 where the average particle velocity is lower than a critical particle velocity of the feedstock.

9. The method of claim 8 where the average particle velocity is 0.1 to 0.9 times the critical particle velocity.

10. (canceled)

11. The method of claim 1 where the particle size distribution has a nominal size of: 1 micron or more; 45 μM or more; between 45 and 300 μm; or between 45 and 150 μM.

12. (canceled)

13. (canceled)

14. (canceled)

15. The method of claim 1 where pressure waves are generated in a regular pulse train, the pulse train having a frequency of 1 to 100 Hz.

16. The method of claim 15 where the frequency of the pulse train is from 5 to 80 Hz.

17. The method of claim 1 where the feeding rate of the particulate material is from 1 to 100 g/min, or the porous coating has a porosity from 10% to 50%.

18. (canceled)

19. The method of claim 17 where the porous coating has a porosity from 20% to 40%.

20. The method of claim 1 where the particulate material consists of metallic particles, cermets, or a combination of metal particles with ceramic particles with less than 10 wt. % ceramic content.

21. (canceled)

22. The method of claim 1 where the particulate material consists essentially of: iron, copper, nickel, titanium, aluminum, chromium, zirconium, zinc, an alloy thereof, or a mixture thereof.

23. The method of claim 22 where particulate material consists essentially of: titanium, copper, nickel, CoNiCrAlY, or stainless steel.

24. The method of claim 1 where the gas is nitrogen or air.

25. The method of claim 1 where maintaining the gas in the gas supply at a temperature lower than the melting point of the particulate material comprises maintaining a temperature of the gas from about 50° C. to about 1000° C.

26. The method of claim 1 where the pressure of the gas in the gas supply is between 250 and 800 psi; the amplitude of the pressure wave is from 1 MPa to 7 MPa; or the coating is performed under atmospheric pressure.

27. (canceled)

28. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order that the invention may be more clearly understood, embodiments thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which:

[0048] FIG. 1 is a schematic side cross-section view of a SWIS device;

[0049] FIG. 2 is a flowchart for a method for producing a porous coating using a SWIS device, in accordance with an embodiment of the present invention;

[0050] FIG. 3 is a micrograph image of Wah Chang CP Ti powder feedstock −75/+45 μm;

[0051] FIG. 4 is a micrograph image of Reading Ti alloy powder feedstock −149/+44 μm;

[0052] FIG. 5 is a micrograph image of a coating produced using the powder of FIG. 3;

[0053] FIG. 6 is a micrograph image of a coating produced using the powder of FIG. 4;

[0054] FIG. 5A is an enlarged micrograph image of the coating of FIG. 5;

[0055] FIG. 6A is an enlarged micrograph image of the coating of FIG. 6;

[0056] FIG. 7 is a micrograph image of a coating produced using CoNiCrAlY powder feedstock −45/+20 μm;

[0057] FIG. 8 is a micrograph image of a coating produced using CoNiCrAlY powder feedstock −38/+10 μm;

[0058] FIG. 9 is a micrograph image of a coating produced using CoNiCrAlY powder feedstock −23/+5 μm;

[0059] FIG. 10 is a micrograph image of a coating produced using coarse Cu powder feedstock at 30 Hz operation of the SWIS device;

[0060] FIG. 11 is a micrograph image of a coating produced using fine Cu powder feedstock at 30 Hz operation of the SWIS device;

[0061] FIG. 12 is a micrograph image of a coating produced using fine Cu powder feedstock at 50 Hz operation of the SWIS device;

[0062] FIG. 13 is a micrograph image of a coating produced using Ni feedstock powder (Amperit) with a porosity of 17% and pore size below 142 μm;

[0063] FIG. 14 is a micrograph image of a coating produced using Ni feedstock powder (Amperit) with a porosity of 26% and pore size below 400 μm;

[0064] FIG. 15 is a micrograph image of a coating produced using Ni feedstock powder (Praxair) with a porosity of 23%;

[0065] FIG. 16 is a micrograph image of a coating produced using Ni feedstock powder (Praxair) with a porosity of 20%;

[0066] FIG. 17 is a micrograph image of a coating produced using stainless steel feedstock powder and pore size below 800 μm; and

[0067] FIG. 18 is a micrograph image of a coating produced using stainless steel feedstock powder and pore size below 360 μm.

DETAILED DESCRIPTION

[0068] In general terms, the present disclosure concerns a method for producing a porous coating using a ShockWave Induced Spraying (SWIS) device. The porous coating is produced and deposited on a substrate. The coating and substrate may form an implant, such as an orthopedic implant, or on an electrode, or the coating may be an abradable seal or a fluid exchange media. The method comprises spraying a particulate material using a SWIS device, while preheating the particulate material to a preheat temperature prior to delivery to a tubular chamber for shockwave pressurization, and maintaining supplied gas at a temperature lower than the melting point of the particulate material, to spray the particulate material at an average particle velocity; wherein, an amplitude and a frequency of the pressure wave, the preheat temperature, a feeding rate of the particulate material and the particle size distribution of the particulate material are chosen so that the average particle velocity allows a deposition of the particles while limiting a deformation of the particles to ensure that the porous coating is produced on the substrate.

[0069] FIG. 1 is a schematic illustration of a SWIS device 100. The SWIS device 100 has a tubular chamber 106 having a substantially uniform cross-sectional area (in comparison with a deLaval type nozzle used in cold spray) with a spray nozzle 108 at a far end. The spray nozzle 108 may be chamfered at the nozzle end with an angle of less than 0.5°, over the last 8% of the extent of the tubular chamber 106, as was the WaveRider device used to demonstrate the present invention. The tubular chamber 106 is y coupled at a near end to both powder supply 116 and gas supply 112. The uniform cross-sectional area along the length of the tubular chamber 106 allows the gas flow travelling down the tubular chamber 106 to be maintained at a substantially constant temperature. This constant temperature delivers the particulate material 104 to substrate 122 with a higher temperature, and is found to provide increased deposition efficiency, at lower velocity, and indeed below the critical velocity limit of cold spray deposition. The gas temperature may be between about 50° C. to about 1000° C., or about 500° C. to about 900° C., depending on the feedstock material.

[0070] A gas supply 112 is in controlled fluid connection with the y coupler. The gas contained in the gas supply 112 is pressurized to a pressure higher than that of the tubular chamber 106, using known pressurized gas supplies, valves, and heaters, preferably with the valves upstream of the heater. The pressure of the gas in the gas supply 112 may be between 250 and 1000 psi. The connection of the gas supply 112 with the inside of the tubular chamber 106 is controlled by a first valve, located between the pressurized gas supply and the heater. The first valve allows a control of the gas flow into the tubular chamber 106 of the shockwave induced spraying device 100.

[0071] The SWIS device 100 further comprises a powder feeding system 116 for feeding particulate material 104 to an inside of the tubular chamber 106 via they coupler. The powder feeding system 116 includes a container for holding a feedstock powder 104, that is connected to the tubular chamber 106. The powder feeding system 116 allows for controlled delivery of particulate material 104 to the tubular chamber 106. For example, the feeding rate of the particulate material 104 can be from 1 to 100 g/min. This control is shown to be provided by an optional second valve 118 between the powder feeding system 116 and the tubular chamber 106 to regulate the amount and/or timing of particulate material 104 being fed to the tubular chamber 106. In the embodiment used for proof of concept, the SWIS device, referred to herein is the WaveRider system, uses a volumetric powder feeder for varying a federate, by changing a rotation speed of a wheel, however a valve 118 may be preferred in future embodiments. It will be noted that by leaving the second valve 118 open or partially open during the pressurization of the chamber 106, pulses of pressure expand into the powder feeding system 116 at the regularity of the pressure waves. This is effective for decreasing a speed with which the powder jet strikes the surface, in accordance with the present invention.

[0072] The powder feeding system 116 further includes a heater 120 for preheating the particulate material 104 to a preheat temperature prior to its delivery into the tubular chamber 106. The preheat temperature may be substantially similar to the gas temperature, which can contribute to an increased deposition efficiency. The preheat temperature may be between 50° C. to 1000° C. The preheat temperature to which the particulate material 104 is preheated is preferably a fraction less than one, of the melting point of the particles or a lowest melting point of the constituents thereof; for example the fraction ranging from 0.15 to 0.7, or more preferably from 0.3 to 0.6.

[0073] A particulate material 104 is provided in the container. The particulate material 104 may be metallic particles, cermet particles, or a combination of metal and ceramic particles. Particles of the particulate material 104 have a melting point and a given particle size. In an embodiment, the particulate material be a metal such as iron, copper, nickel, titanium, aluminum, chromium, zirconium and zinc. The particles can also comprise an alloy of those metals. In the embodiment wherein the particulate material also comprises ceramic particles, the ceramic particles can comprise titania, zirconia, alumina or a combination thereof, with total ceramic content being less than 20 wt. %, more preferably less than 10 wt. %, more preferably less than 5 wt. %. The particles may have a nominal size greater than 1 micron, such as a nominal size from 45 to 300 microns, or from 45 to 150 micron. The powders may have any morphology, granulometry, coating or structuration, as these features of powders are known to improve or alter deposition efficiency, porosity, or adhesion properties.

[0074] Using the SWIS device 100, the SWIS process (also known as pulsed gas dynamic spray) accelerates feedstock powder particles with a gas maintained at a lower temperature than the melting point of the powder(s). In order to do so, pulses of a high pressure gas are induced in a tube, thereby creating shockwaves that accelerate the particles towards the substrate. Hence, the SWIS process is inherently a discontinuous process. Of note, the powder temperature is maintained at substantially the same temperature as the gas, contrary to the cold spray deposition, where a supersonic nozzle further accelerates and cools down the particles.

[0075] The SWIS process may involve adjusting a rate of the powder injection, the powder temperature, as in other thermal and cold spray processes, but additionally allows for adjustment of a rate of the opening of the first valve (or the relative opening and closing timings of first and second (118) valves), which is particularly useful for controlling powder acceleration. We here show that powder particles can be projected at the gas temperature with speeds that reduce the deformation of the particles upon impact, while ensuring an adequate coating formation in terms of deposition efficiency and deposition rate. The SWIS process can generate porous coatings by depositing with slower speeds and with lower deformation levels than cold spray.

[0076] In comparison with vacuum deposition, the coating can be done under atmospheric pressure and does not require a vacuum deposition chamber. This makes the deposition easier than with vacuum plasma spray method (no need to generate a vacuum with a pressurized gas emitting particulate spray nozzle, faster cycle time, no maintenance of the vacuum system). The size of the object to be coated is not restricted to the size of the vacuum chamber.

[0077] According to a first aspect of the invention and referring to FIG. 2, there is provided a method 10 for producing a porous coating 102 using SWIS device 100. The method 10 includes the following steps.

[0078] A particulate material 104 is provided at step 12. The particulate material 104 is suitable for the SWIS process as described above. The SWIS device 100 is then provided step 14. The SWIS device 100 is preferably the WaveRider System™ or a modified WaveRider System™ with the valve 118 as shown in FIG. 1. A gas in the gas supply 112 is provided at a temperature lower than the melting point of the particulate material 104 (step 16) and the spraying end 108 of the SWIS device 100 is directed towards the substrate 122 to be coated (step 18). The particulate material 104 is then dispensed into the tubular chamber 106 by the powder feeding system 116 in a controlled manner (step 20). The feeding of the particulate material 104 into the tubular chamber 106 may occur at regular time intervals with variable, or constant, amounts of the particulate material 104 entering the tubular chamber 106 in each interval (in steady state). This amount may influence a speed at which the particulate material 104 exits the spraying end 102. The controlled manner of dispensing the particulate material 104 further comprises preheating the powder to a temperature that is also below the melting point, with heater 120.

[0079] The gas supply is actuated to generate a pressure wave, by opening and closing the first valve, which is a part of gas supply 112. The pressure wave is propagated through the tubular chamber 106 from the gas inlet 110 to the spraying end 108 (step 22). The pressure wave accelerates the particulate material 104 longitudinally through the spraying end 108, and is projected onto the substrate with an average particle velocity.

[0080] The pressure wave can be generated by opening and the closing the first valve at a given rate to produce a regular series of pressure waves. As the pressure waves are generated, particulate material 104 injected since the last feed, is projected at each pulse.

[0081] In this method, the amplitude and the frequency of the pressure wave, the preheat temperature, the feeding rate of the particulate material and/or the particle size of the particulate material can be adjusted so that the average particle velocity allows a deposition of the particles while limiting the deformation of the particles (step 24). The amplitude of the pressure wave may be from 1 to 7 MPa, or more preferably from 2 to 4 MPa. The frequency of the pressure waves can be from 1 to 100 Hz, more preferably from 5 to 40 Hz.

[0082] The steps of this method are not inherently ordered, in as much as there are continuous processes for feeding powder, heating powder, heating gas, supplying gas in pulses, and moving the nozzle with respect to the substrate to produce coatings, as will be appreciated by those of skill in the art.

[0083] Limiting the deformation of the particles can result in a coating that is porous in contrast to a dense coating, in which particles are highly deformed. The average particle velocity must be sufficient to ensure an adhesion of the particles to the substrate 122, but also low enough to limit the deformation of the particles, for example, so that a porous coating can be obtained. The average particle velocity that allows deposition of a porous coating may be lower than a critical particle velocity. Herein the critical particle velocity is the minimal impact velocity required for the particles to be deposited on a substrate with at least 10% deposition efficiency is reliably produced. The critical particle velocity is determined by time of flight particle measurement on cold spray conditions at which 10% deposition efficiency is observed. The average particle velocity may be from 0.1 to 0.9 times the critical particle velocity, more preferably from 0.3 to 0.7 times the critical particle velocity.

[0084] The average particle velocity depends on the particle size, the pressure amplitude of the pressure wave and a length of time that the first valve is opened. Thus the average particle velocity can be reduced by: using a coarser particulate material; decreasing the pressure of the gas in the gas supply 112; or decreasing a time that the first valve is opened. Applicant also finds a variation based on a frequency of the pressure waves, for some feedstocks.

[0085] Moreover, the average particle velocity as well as the particles size distribution can influence a porosity of the porous coating. The porous coating may have a porosity ranging from 10% to 50%, or more preferably from 20% to 40%, as measured using ASTM B962.

[0086] Optionally, the coating of the substrate 122 may be followed by a heat treatment to improve metallic bonds at an interface between the particles. The heat treatment may be annealing. For titanium coatings, the heat treatment can advantageously be performed below 1000° C., reducing damage to, and increasing a range of, suitable substrates. If the metal is reactive at the temperature of the heat treatment, it is performed in a protected environment, such as an argon atmosphere or in a vacuum.

Example 1 Ti

[0087] Two types of titanium powder particles (Wah Chang CP Ti −75/+45 μm and Reading Ti alloy −149/+44 μm) were shockwave induced sprayed onto Ti6Al4V cylindrical tensile (d=1″) and shear (d=0.75″) substrates using the WaveRider system, which is substantially as shown in FIG. 1, except that the valve 118 is not provided. Further details on this system is provided, for example in Journal of Thermal Spray Technology, v20(4)pp. 866-881, June 2011), which is incorporated herein by reference. The WaveRider system was used following parameters:

TABLE-US-00002 Gas Nitrogen Gas temperature 800° C. Pressure 600 psi Frequency 30 Hz DDP 25 mm Powder temperature 600° C. Powder rate 2.7 g/min (Wah Chang); 4.9 g/min (Reading) Step size 2 mm Robot speed 10 mm/sec # pass 1

Table 2. Parameters Used for Shockwave Induced Spraying

[0088] Post deposition, the samples were subjected to a heat treatment for 1 hr at 850° C. in a high vacuum (diffusion pump) furnace.

[0089] The Wah Chang and Reading powders were examined, and are shown as FIGS. 3, 4, respectively. Preliminary experiments conducted without the post-deposition heat treatment showed partial metallic bonds at the interface between particles and the coating-substrate interface. After heat treatment, good interparticle metallurgical contact was created with both powders. Heat treatment did not cause important modification of the uncoated substrate surface as practically no thermal etching lines were observed on the Ti6Al4V.

[0090] FIGS. 5, 6 are coating cross-section images of the heat treated coatings produced respectively from the Wah Chang and Reading powders. Coating thickness for both samples varied from 0.7 to 1.1 mm, probably associated with a non-optimized step size and/or frequency/traverse speed. FIGS. 5A, and 6A are enlarged views near the substrate interface of the same coatings. Scanning electron microscopy examination of shockwave induced sprayed porous titanium coatings using Wah Chang and Reading particle powders shows excellent surface roughness and gripping. Porosities of 37 and 33% were obtained using Wah Chang and Reading powders respectively, both within the range obtained with vacuum plasma spray. Deposition efficiency was 51 and 60% using Wah Chang and Reading powders, respectively. Larger pores were obtained using Reading powder, likely due to the larger particle size distribution.

[0091] Shear and tensile tests were performed on both groups to evaluate the shear and tensile strengths of the porous coatings. Both groups ruptured in the adhesive used to join adjacent parts during tensile and shear testing. This translates in shear strength >31.7±3.6 MPa and tensile strength >69 MPa for samples fabricated using Wah Chang powders and shear strength >31.3±1.4 MPa and tensile strength >69 MPa for coatings composed of Reading powders. These properties are much higher than the ASTM standard requirement for shear (20 MPa) and tensile (22 MPa) strengths. Heat treatment post-deposition was required to obtain strong bonding properties as shear and tensile strengths of samples ‘as sprayed’ were well under the targeted standard requirements. In applications where the mechanical strength are not critical (e.g.: electrodes), the material could be used without heat treatment.

Example 2 CoNiCrAlY

[0092] Scanning electron microscopy examination of CoNiCrAlY coatings deposited via SWIS are shown as FIGS. 7-9. Microstructure and porosity of the coatings (even the pore size) can be tuned by choosing the appropriate granulometry of the powder feedstock and spray parameters. Specifically these coatings were produced with the same process parameters as for the Ti coatings, except: the gas pressure was 700 psi; DDP was 5 mm; the powder temperature was at room temperature; the powder feed rate was not monitored; and the step size was 1 mm; the traverse speed was 5-10 mm/s; and the coating was deposited in 3-5 passes. Coatings deposited using Oerlikon Metco feestock powders having sizes −45/+20 μm, −38/+10 μm, and −23/+5 μm resulted in coating with porosities of 16.4%, 30.5%, and 22% respectively, as shown in FIGS. 7, 8 and 9.

Example 3 Cu

[0093] Two types of copper powder particles (Plasma Giken PG-PMP-1015 coarse 75 μm and Plasma Giken PG-PMP-1012 fine 20 μm) were SWIS sprayed onto mild steel substrates to form coatings. SEM images of these coatings are provided as FIGS. 10, 11, and 12. Specifically these coatings were produced with the same process parameters as for the Ti coatings, except: the gas temperatures ranged from 300-400° C.; DDP was 20 mm; the powder temperatures were unheated; powder rate was not monitored; step size was 1 mm; traverse speed was only 5 mm/s; the coating was produced in 2 passes; and a different frequencies (e.g. 30-50 Hz) were used in the different coatings. Coating microstructure, porosity and pore size can be tuned over a wide range by choosing the appropriate granulometry of the powder feedstock and spray parameters. Porosity of 7% and 20% were produced with pore sizes below 142, 100, and 215 microns. FIGS. 10 and 11 show 7% porosities with the coarse and fine powders, respectively, and FIG. 12 shows 20% porosity with the fine powder at the higher frequency pulse train.

Example 4 Ni

[0094] Three types of nickel powders e.g. Praxair Ni101 (−45/+11 μm), Praxair Ni 969 (−75/+45 μm) and HC Starck Amperit 176.068 (−35/+15 μm) were deposited according to the invention, onto mild steel substrates. Specifically these coatings were produced with the same process parameters as for the Ti coatings, except: the gas temperatures ranged from 500-600° C.; DDP was 10 mm; the powder temperatures were unheated; powder rate was not monitored; step size was 1 mm; traverse speed was 5 to 10 mm/s; and the coating was produced in 2 passes. Porosities of 17-26% were produced with pore sizes below 400, 350, and 142 μm.

Example 5 Stainless Steel

[0095] Stainless steel SS316L feedstock from Sandvik was deposited according to the invention, onto mild steel substrates. The feedstock had a particle size distribution −75/+45 μm. Specifically these coatings were produced with the same process parameters as for the CoNiCrAlY coatings, except that the DDP was 20 mm, traverse speed was 5 mm/s; and the coating was produced in 2 passes.

[0096] None of these experiments leveraged the powder heating capabilities of the WaveRider device, and it is considered that preheating the powders will allow for deposition at lower velocities, to produce higher porosity coatings, with higher deposition efficiencies. The results clearly show that a wide range of metals, and likely cermets with low ceramic content, can be sprayed to produce porous coatings in accordance with the present invention.

[0097] Other advantages that are inherent to the structure are obvious to one skilled in the art. The embodiments are described herein illustratively and are not meant to limit the scope of the invention as claimed. Variations of the foregoing embodiments will be evident to a person of ordinary skill and are intended by the inventor to be encompassed by the following claims.

REFERENCES

[0098] 1. Ryan G, Pandit A, Apatsidis D P. Fabrication methods of porous metals for use in orthopaedic applications. Biomaterials 2006; 27: 2651-2670. [0099] 2. Matassi F, Botti A, Sirleo L, Carulli C, Innocenti M. Porous metals for orthopedics implants Clinical Cases in Mineral and Bone Metabolism 2003; 10(2):111-115. [0100] 3. Messersmith P B, Cooke F W. Stress enhancement and fatigue susceptibility of porous coated Ti-6Al-4V implants: an elastic analysis. J Biomed Mater Res 1990; 24: 591-604. [0101] 4. Simmons C A, Valiquette N, Pilliar R M. Osseointegration of sintered porous-surfaced and plasma spray-coated implants: An animal model study of early postimplantation healing response and mechanical stability. J. Biomed Mater Res 1999, 47, 127-138. [0102] 5. Wolfarth D, Ducheyne P. Effect of a change in interfacial geometry on the fatigue strength of porous-coated Ti-6A1-4V. J Biomed Mater Res 1994; 28:417-25. [0103] 6. Yue S, Pilliar R M, Weatherly G C. The fatigue strength of porous-coated Ti-6% Al-4% V implant alloy. J Biomed Mater Res 1984; 18:1043-58. [0104] 7. Martell J M, Pierson III R H, Jacobs J J, Rosenberg A G, Maley M, Galante J O. Primary total hip reconstruction with a titanium fiber-coated prosthesis inserted without cement. J Bone Joint Surg Am 1993; 75:554-71. [0105] 8. Ducheyne P. Orderly oriented wire meshes as porous coatings on orthopaedic implants I: Morphology. Clinical Materials 1986; 1:59-67. [0106] 9. Fabi D W, Levine B R. Porous Coatings on Metallic Implant Materials. ASM Handbook, Volume 23: Materials for Medical Devices. 2012:307-319. [0107] 10. U.S. Pat. No. 7,854,958B2 [0108] 11. Gardon M, Latorre A, Torrell M, Dosta S, Fernandez J, Guilemany J M. Cold gas spray titanium coatings onto a biocompatible polymer. Materials Letters. 2013:97-99. [0109] 12. Price T S, Shipway P H, McCartney D G. Effect of cold spray deposition of a titanium coating on fatigue behavior of a titanium alloy. Journal of Thermal Technology. 2006; 15 (4): 507-512. [0110] 13. Marrocco T, McCartney D G, Shipway P H. Production of titanium deposits by cold gas dynamic spray. TWI. 2005. [0111] 14. Li C J, Li W Y. Deposition characteristics of titanium coating in cold spraying. Surface and Coatings Technology. 2003; 167:278-283. [0112] 15. Choudhuri A, Mohanty P S, Karthikeyan J. Bio-ceramic composite coatings by cold spray technology. ASB Industries. [0113] 16. Qiu D, Zhang M, Grondahl L. A novel composite porous coating approach for bioactive titanium-based orthopedic implants. Society for Biomaterials. 2012:862-872. [0114] 17. Sun J, Han Y, Cui K. Innovative fabrication of porous titanium coating on titanium by cold spraying and vacuum sintering. Materials Letters. 2008; 62:3623-3625. [0115] 18. Li W Y, Zhang C, Guo X, Xu J, Li C J, Liao H, Coddet C, Khor K A. Ti and Ti-6Al-4V coatings by cold spraying and microstructure modification by heat treatment. [0116] 19. Vo P, Irissou E, Legoux J G, Yue S. Mechanical and microstructural characterization of cold-sprayed Ti-6Al-4V after heat treatment. [0117] 20. Zahiri S H, Fraser D, Jahedi M. Recrystallization of cold spray-fabricated CP titanium structures. Journal of Thermal Spray Technology. 2009; 18(1):16-22. [0118] 21. R. E. Blose, B. H. Walker, R. M. Walker, and S. H. Froes, New Opportunities to Use Cold Spray Process for Applying Additive Features to Titanium Alloys, Met. Powder Rep., 2006, 61(9), p 30-37 [0119] 22. R. Blose, Spray Forming Titanium Alloys Using the Cold Spray Process, Thermal Spray 2005: Thermal Spray Connects: Explore Its Surfacing Potential!, E. Lugscheider Ed., ASM International, Materials Park, O H, 2005, p 199-207 [0120] 23. W. Y. Li, X. P. Guo, C. Verdy, L. Dembinski, H. L. Liao, C. Coddet, Scr. Mater. 2006, 55, 327. [0121] 24. T. Stoltenhoff, C. Borchers, F. Gärtner, H. Kreye, Surf. Coat. Technol. 2006, 200, 4947. [0122] 25. H. Y. Lee, S. H. Jung, S. Y. Lee, K. H. Ko, Mater. Sci. Eng. A 2006, 433, 139. [0123] 26. W. Y. Li, C. J. Li, and H. L. Liao, Effect of Annealing Treatment on the Microstructure and Properties of Cold-Sprayed Cu Coating, J. Therm. Spray Technol., 2006, 15(2), p 206-211 [0124] 27. U.S. Pat. No. 8,298,612B2 [0125] 28. M. Karimi, G. W. Rankin, B. Jodoin, “Shock-wave induced spraying: Gas and particle flow and coating analysis”, Surface and Coatings Technology, Volume 207, August 2012, p. 435-442 [0126] 29. M. Yandouzi, H. Bu, M. Brochu and B. Jodoin, “Nanostructured Al-Based Metal Matrix Composite Coating Production by Pulsed Gas Dynamic Spraying Process”, Journal of Thermal Spray Technology, 2012, Volume 21, Numbers 3-4, Pages 609-619 [0127] 30. B. Jodoin, P. Richer, G. Bérubé, L. Ajdelsztajn, M. Yandouzi, “Pulsed-Gas Dynamic Spraying: Process Analysis, Development and Selected Coating Examples”, Surface and Coatings Technology, Volume 201 (16-17), May 2007, p. 7544-7551 [0128] 31. U.S. Pat. No. 8,192,792B2