Low-Temperature Spray Process Creates Adherent and Continuous Coatings of Fine-Grained and Nano-Sized Metal Powders

Howard Gabel, President, Inovati, Santa Barbara, CA

MRS Bulletin, February, 2003, Page101

A low-temperature metal spray coating technology has been developed from obser- vations made by its inventors during particle impact studies conducted at the NASA White Sands Test Facility, Las Cruces, New Mexico. The patented process plus specifical- ly designed spraying apparatus are being further developed and commercialized by the U.S. company, Inovati, in Santa Barbara, Calif. The spray apparatus has been improved over past versions with respect to accelerant gas formulation, powder feeding, spray nozzle design, and the spray parame- ters for optimal film quality and adhesion..

Oxidation behavior of Cu–Cr environmental barrier coatings on Cu–8Cr–4Nb

Linux U. Ogbuji, NASA Glenn Research Center, Cleveland, OH

Surface and Coating Technologies, Volume 197, March 31, 2005, Pages 327-335

Oxidation behavior of some Cu–Cr alloys (with 8.5–25.6 wt.% Cr, in both stand-alone coupons and spray coatings on Cu–8Cr–4Nb) was studied by TGA and cyclic oxidation. Judging by the more stringent cyclic oxidation results, protection of the substrate Cu–8Cr–4Nb was effective for the whole 10-h duration of testing up to 750 8C only for coatings with 21% or higher Cr. Similar protection was exhibited by Cu–17Cr only up to 650 8C, and only for b3 h at 750 8C. In all cases the Cr2O3 subscale nucleated discretely (and always under a non-adherent scale of Cu oxides), and passive protection did not start until the nuclei joined into a continuous barrier and parabolic oxidation kinetics set in. The only protection achieved before that stage of Cr2O3 coalescence was via sacrificial oxidation of the coating...

Heat treatment of cold spray coatings to form protective intermetallic layers

K. Spencer, M.-X. Zhang

Scripta Materialia, Volume 61, Issue 1, July 2009, Pages 44-47, ISSN 1359-6462

A new technique for generating thick Mg/Al intermetallic coatings on Mg-Al-Zn alloys through post-spray annealing of aluminium cold spray coatings is discussed. Annealing at 400 [degree sign]C, which is close to the solution treatment temperature for AZ91 alloy, results in the formation of thick Mg17Al12 and Al3Mg2 intermetallic layers. These layers have high hardness, and increase the corrosion resistance to a level similar to that of aluminium alloys...

Ni-based fully amorphous metallic coating with high corrosion resistance

Wang, A. P., Zhang, T., and Wang J.Q.
Philosophical Magazine Letters, 86 (1) (2006), pp. 5-11

A new technique for generating thick Mg/Al intermetallic coatings on Mg-Al-Zn alloys through post-spray annealing of aluminium cold spray coatings is discussed. Annealing at 400 [degree sign]C, which is close to the solution treatment temperature for AZ91 alloy, results in the formation of thick Mg17Al12 and Al3Mg2 intermetallic layers. These layers have high hardness, and increase the corrosion resistance to a level similar to that of aluminium alloys...

Coatings: Kinetic Metallization, 2004 MDA Technology Applications Report

Robinson, T.
Missile Defense Agency, Advanced Applications Program, 2004, pp. 36-37

The Naval Surface Warfare Center (NSWC) Carderock Division is responsible for all technical aspects of improving performance of ships, submarines, military watercraft, and unmanned vehicles for the Navy. The NSWC recently installed a Kinetic Metallization (KM) coating devel- opment system developed by Inovati. KM is a solid-state deposition process that creates and applies corrosion-resistant coatings. Conventional thermal spray coatings tend to be ineffective in seawater because they are excessively porous, which allows seawater to seep through. KM allows the deposition of fully dense coatings, minimizing porosity and in turn reducing cor- rosion. Thermal spray also contains scattered concentrations of oxides, which create pathways for the corrosion process. KM coatings have oxides evenly distributed throughout, which creates a more uniform microstructure that blocks the corrosive properties of sea water...

Kinetic Metallization Compared with HVOF

Gabel, H.
Advanced Materials & Processes, May 2004, ASM International, Metals Park, OH

Kinetic metallization (KM) is a solid-state process in which metallic powders are sprayed through aspeciallydesigned,twophase, sonic deposition nozzle that accelerates metal particles entrained in an inert carrier gas. Once accelerated to high speed, the particles are directed onto a substrate, onto a mandrel, or into a mold. Subsequent high-speed collision of the metal particles causes very large strain (approximately 80% in the di- rection normal to impact) in the parti- cles. This deformation results in a huge increase in particle surface area (ap- proximately 400%), producing a new surface that is oxide free. When these active surfaces come into contact, pure metallurgical bonds are formed. Met- allurgical bonding is achieved exclu- sively through the solid-state reaction, with no bulk melting...

Low Temperature Metal Coating Method, Lawrence Livermore National Laboratory

Gabel, H.
CRADA No. TSB-1155-95 (Livermore CA, University of California, April 3, 2000).

A new metal coating method, called KEM (kinetic energy metallization), demonstrated in the laboratory by Inovati, utilized fast-moving solid particles entrained in a gas that are caused to flow through a nozzle to effect particle deposition on metal surfaces at room temperature conditions. This method (US Patent 5,795,626) was an attractive and viable alternative to the currently available high-temperature coating methods available...

The Solid-State Spray Forming of Low-Oxide Titanium Components

Tapphorn, RM. and Gabel, H.
Journal of Metals, 50 (9) (1998), pp. 45-46,76.

This paper presents a novel approach for the production of essentially oxide- free titanium parts in near-net shapes. The hydride-dehydride (HDH) process is used to produce oxide-free titanium (OFTi) powder; the powder is then used as feedstock for the solid-state spray forming (SSF) process. Older spray form- ing techniques (e.g., thermal, Osprey, and low-pressure plasma spray)1–4 are not particularly suited to the production of parts of near-net shape and typically introduce supplementary oxidation...

Solid-State Spray Forming of Aluminum Near-Net Shapes

Gabel, H. and Tapphorn, R. M.
Journal of Metals, 49 (8) (1997) pp. 31-33.

Osprey and low-pressure plasma spray (LPPS are two liquid-phase spray forming processes used to produce aluminum and aluminum metal-matrix composites (MMCs). The Osprey process is a method for spray forming aluminum components that uses sequential stages of atomization and droplet consolidation. Invented in 1970, the Osprey process is controlled by Osprey Metals of Neath, Wales. Licensees for aluminum deposition include Alcan (United Kingdom), Peak (Germany), Alusuisse (Switzerland), Pechiney (France), Sumitomo Light Metals (Japan), and Alcoa (United States). To improve the performance of the traditional Osprey process, recent research conducted at the Idaho National Engineering Laboratory focused on using DeLaval nozzles. High-speed deposition of liquid droplets with DeLaval nozzles is the liquid analog of the solid-state spray forming (SSF) processes...

Preliminary Evaluation of KM for Fabrication

Chow, T.S., Kang, S.W., Gabel, H. and Tapphorn, R.M.
Proceedings of the 12th General Meeting of JOWOG 31 (Livermore CA, University of California, 1996).

Kinetic Energy Metallization (KEM) is an emerging deposition process that uses metal powder as feed stock without external heating (Reference 1). Metal powder mixed with gas is accelerated through a supersonic nozzle directed toward the substrate to be coated. Collisions occur between the powder and the substrate, causing fresh active metal to be exposed. When these active surfaces contact one another, they agglomerate and form true metallic bonds.

Surface Modification by High-Speed Macroscopic Particle Collision

Gabel, H. and Tapphorn, R.M. 1995
Proceedings of The Minerals, Metals Materials Society and American Society of Materials International. Surface Modification Technologies IX, edited by T.S. Sudarshan, W. Reitz, and J.J. Stiglich; 1995 Oct 29-Nov 2. (Warrendale, PA:TMS, 1995).

Several new surface modification processes are introduced and described. All employ kinetic energy to form new surfaces exclusively through high speed particle impact - thermal energy is not introduced. These processes represent a previously underutilized regime or particle-substrate interaction that falls between conventional powder based processes and microscopic particles (eg., ion) based processes. Surface interactions are proposed and experimental results correlated to theory. Kinetic Energy Metallization (KEM) and Kinetic Energy Polymerization (KEP) produce coatings through plastic deformation and creation of free surface. These coatings comprise unique microstructural and mechnaical properties. Kinetic Energy Implantation (KEI) modifies surfaces through implantation of rigid particles into malleable substrates. Kinetic Energy Ablation (KEA) removed material through the fracture of the substrate. Each of these processes employs a unique debris recovery system that renders the compliant with the most strict environmental regulations. They are frugal in the use of energy and raw materials.