Thermal Spray Tips - Swinburne University of Technology

Compiled by Jo Ann Gan, Edited and advised by Christopher C. Berndt
Swinburne University of Technology Thermal Spray Group (SwinTS)
Please contact Prof. Christopher Berndt at cberndt @swin.edu.au for further enquiries
5. Coating Processing and Operation
5.1. Part Configuration and Coating Location Considerations
Thermal spray stream positions. (a) Good (b) Acceptable (c) Minimum acceptable (d)
Formation of porosity in sprayed coatings when the spray angle is reduced to approximately
45 degrees. Particles impacting at angles of less than 90 degrees create a shadowing effect
that results in increased coating porosity.
After identifying an area to be coated, determine whether the part is symmetrical about the coating
location, which would allow fixturing for rotation and/or translation about an axis perpendicular to the
spray torch. The stream of spray particles should impact the target surface as close to normal (90
degrees) as possible. The minimum acceptable impact angle is 45 degrees to the target area. A 45
degree spray angle impact should be used only as a last resort, bearing in mind that some coating
property deviation from the optimum can be expected. Both bond strength and adhesion will be
compromised. Porosity increases dramatically as the angle of the spray torch moves from normal to 45
degrees.
Source: Coating Operations, Frank N. Longo, Longo Associates, as published in Handbook of Thermal
Spray Technology, J.R. Davis (Ed.), ASM International, 2005, p 109.
Information and data acquired from ASM International Thermal Spray Society
website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/
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