C. Rupprecht, B. Wielage, G. Paczkowski, H. Pokhmurska, TU Chemnitz, Chemnitz, Germany
In order to guarantee a high quality in the automated production of thermal spray coatings, application of diagnostic tools is becoming more and more popular. Common diagnostic systems used for observing optical emissions of spraying processes analyse the geometry of the spray jet or the in-flight particle parameters. Such optical systems are expensive and not very robust. More economic and easier to apply is the analysis of the acoustic emissions of the spraying process. Depending on the method of thermal spraying, acoustic signals contain extremely useful information that can be used for detecting critical spraying conditions. Application of microphones and vibration pick-ups is tested for HVOF spraying. The results are correlated to machine settings as well as coating properties such as porosity and micro-hardness of WC/Co 88/12 coatings. It is also shown how acoustic analysis helps to improve other spraying technologies. Finally the correlation between the acoustics of real processes and results from computer simulations are investigated.
Summary: Depending on the method of thermal spraying, acoustic signals contain extremely useful information that can be used for detecting critical spraying conditions. Application of microphones and vibration pick-ups is tested for HVOF spraying. The results are correlated to machine settings as well as coating properties such as porosity and micro-hardness of WC/Co 88/12 coatings.
