Available Technology

A Method for Thermal Spraying of Coatings Using Resonant Pulsed Combustion

Cutting-edge thermal spraying system applies metal coatings with improved adhesion and protection
Unlike traditional thermal sprayer systems, this state-of-the-art resonant pulse combustion thermal sprayer is being designed to require no high-pressure fuel or air supply. Instead, fuel is naturally aspirated from the tank through one tube line and into the pulsejet, and air for initial ignition is ported through another line. Once operation begins, this air is no longer needed as additional air is naturally aspirated through the inlet. The feedstock for the metal coating is in rod form and easily inserted through an access port in the side of the device into the combustion chamber, resulting in a less expensive solution as compared to traditional powder coating systems. Thrust from the combustor creates a periodic, high-speed jet, which is emitted from the tailpipe, downstream of the combustion chamber. The metal to be deposited melts in the combustion chamber, and then is carried downstream and ejected from the tailpipe at high speed where it impinges and solidifies on the target surface. The pulsejet operates only long enough to melt the material and deposit it onto the target, so the material spends minimal time in the combustion chamber. This feature avoids overheating and therefore forestalls problematic chemical changes such as oxidation. This non-steady combustion process also generates much higher impingement velocities that greatly enhance adhesion and add durability. NASA's device is mechanically simple and has potential to be used to create a mobile, high-volume spray unit. This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities.
Abstract: 
Innovators at NASA's Glenn Research Center are developing a revolutionary way to apply a protective metal coating to otherwise vulnerable materials. This method takes resonant pulse combustion technology currently used for flight propulsion and makes it available in a handheld thermal spraying system. Normally, thermal spraying involves a steady combustion process that requires a supply of high-pressure fuel and oxidizer to achieve the high velocities necessary for adhesion. This process can lead to material remaining in the heating chamber for long periods of time, increasing the chances of coating-material oxidation. NASA's method of using resonant pulsed combustion in a thermal spray system produces very high velocities without a high-pressure supply, along with very short residence times. These upgrades greatly increase the ease and effectiveness of the coating process, even while reducing its cost.
Benefits: 

Better adhesion: Higher-velocity spray leads to more complete impingement on the surface material.

applications: 

Corrosion protection of steel products, especially in Corrosion Under Insulation (CUI) applications (e.g., in refineries and process plants)

Low-cost system with the potential for mobile coating operations

Surface repair for a wide array of metal components

Reps: 
Patent Number: 
7,763,325
Internal Laboratory Ref #: 
LEW-TOPS-29
Patent Status: 
Patent Issue Date: 
August 11, 2015
Agency
NASA
Region
Midwest
State: 
Ohio
Lab Representatives
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