Offline Acoustic Plasma Spray Nozzle Wear State and Characteristic Identification

Wear of plasma spray nozzles is a documented source of variation in the plasma spray process. Current wear detection relies upon observed gun voltage drops during operation. Operating voltage or hours of operation are rarely recorded when nozzles are changed over resulting in the loss of nozzle wear state knowledge. An offline means of determining wear state of GH type nozzles for SM 9MB plasma spray guns has been developed. By recording and analyzing the acoustic signal of a controlled gas flow through each nozzle, 22 nozzles were accurately categorized by their degree of wear. This test also allowed for the distinction between three manufacturers of new GH nozzles. Degree of wear was determined using bore profilometry and verified by voltage drop. This method allows for improved quality assurance and enhanced useful nozzle life.