One-step methods for creating fluid-tight, fully dense coatings
AssigneePraxair S.T. Technology, Inc.
InventorsDAMING WANG, ARDY S. KLEYMAN, KASEY D. HUGHES
Life of this patent
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Abstract
A fluid tight, fully-densified, coating is prepared by a High Velocity Oxygen Fuel (“HVOF”) process that dilutes oxygen with an inert gas. The inert gas is pre-mixed with oxygen prior to the oxygen entering a combustion chamber. The resultant flame temperature is lowered a controlled amount to eliminate, minimize or reduce oxidation of power feedstock that is injected into the thermal spray torch. The ability to reduce the flame temperature allows a relatively smaller particle feedstock to be deposited without significant oxidation. The dilution process creates an as-deposited fully-dense, fluid tight coating.
Claims18
A one-step method for creating a thin, fluid-tight, as-deposited coating without sealing the as-deposited coating, comprising:
- providing a substrate;
- providing a powder feedstock having a particle size ranging from 1 to 15 microns;
- providing a thermal spray torch, said thermal spray torch comprising a combustion chamber with a comprising a nozzle downstream of the combustion chamber;
- introducing a fuel into the combustion chamber;
- pre-mixing oxygen gas with an inert gas to produce diluted oxygen gas, wherein the pre-mixing occurs prior to the oxygen gas entering the combustion chamber, and wherein a flow ratio of the inert gas to the oxygen gas ranges from 8:92 to 50:50;
- introducing the diluted oxygen gas into the combustion chamber;
- combusting the fuel with the diluted oxygen gas to generate a flame;
- introducing the powder feedstock into the nozzle;
- contacting the powder feedstock with the flame to produce substantially molten and semi-molten droplets;
- and
- directing the substantially molten and semi-molten droplets to the substrate.
A one-step method for creating a thin, fluid-tight, as-deposited coating without sealing the as-deposited coating, comprising:
- providing a substrate;
- providing a powder feedstock having a particle size ranging from 1 to 15 microns;
- providing a thermal spray torch, said thermal spray torch comprising a combustion chamber and said torch further comprising a nozzle downstream of the combustion chamber enclosed therein;
- introducing a fuel into the combustion chamber;
- pre-mixing oxygen gas with an inert gas to produce diluted oxygen gas;
- directing the diluted oxygen gas into the combustion chamber;
- combusting the fuel with the diluted oxygen gas to generate a flame within the combustion chamber;
- controlling a flame temperature in the combustion chamber;
- introducing the powder feedstock into the nozzle;
- heating the powder feedstock to produce substantially molten or semi-molten droplets with reduced oxidation in comparison to conventional high velocity oxygen fuel processes using the powder feedstock with the particle size ranging from 1 to 15 microns.
The one-step method of clam 9, wherein a total flow rate of oxygen and nitrogen is 500-3000 scfh.
A thin, fluid-tight, as-deposited, one-step thermal spray coating without sealer created by an oxygen dilution High Velocity Oxygen Fuel (“HVOF”) process, said coating derived from a tungsten carbide-based powder composition with a particle size ranging from 1-15 microns and a coating thickness no greater than 100 microns, wherein the fluid-tightness is characterized by an absence of visually detectable fluid leakage at pressures of 10,000 psi or greater, and a fully dense structure as defined by an absence of interconnected pores.
Dependencies are inferred from the claim text.