RE: How does gas-shroud HVOF (warm spray) system work?
I don't see how a shroud gas could possibly impart any additional velocity to the particles. In order to accelerate the JP5000 gas stream, you must expand it after the choke. Introducing additional gas in the nozzle is going to compress the gas stream. Would you post the article to which you are referring?
Warm spray is a strange technological development, in my opinion. By quenching the flame with nitrogen, the operator is basically synthesizing air. In other words, they are turning a JP5000 into an HVAF gun. They get some nice looking coatings, of course, because they are synthesizing the HVAF spray conditions. However, in the process, they still have the same drawbacks of the JP, namely radial powder injection, water cooling, short nozzle life, etc. If the researchers would start with an HVAF gun, they could also take advantage of HVAF's lower operating cost, higher deposit efficiency, and longer component life.
|