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
2. Thermal Spray Processes
2.1. Comparison of Major Coating Methods
Characteristic Electro/electroless
plating
General Characteristics of Major Coating Methods
Thermal spray Chemical vapor
deposition
Information and data acquired from ASM International Thermal Spray Society
website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/
Physical vapor
deposition
Equipment cost Low Low to moderate Moderate Moderate to high
Operating cost Low Low to moderate Low to moderate Moderate to high
Process
environment
Aqueous solution Atmospheric to
soft vacuum
Atmospheric to
medium vacuum
Hard vacuum
Coating geometry Omnidirectional Line of sight Omnidirectional Line of sight
Coating thickness Moderate to thick,
10 μm-mm
Substrate
temperature
Adherence Moderate
mechanical bond to
very good chemical
bond
Surface finish Moderately coarse
to glossy
Thick, 50 μm-cm Thin to thick, 0.1
μm-mm
Low Low to moderate Moderate to high Low
Good mechanical
bond
Coating materials Metals Powder/wire,
polymers,
metals/ceramics
Very good
chemical bond to
excellent diffusion
bond
Very thin to
moderate
Moderate
mechanical bond
to good chemical
bond
Coarse to smooth Smooth to glossy Smooth to high
gloss
Metals, ceramics,
polymers
Metals, ceramics,
polymers
Major coating methods include electro/electroless plating (EP/ElsP), chemical vapor deposition (CVD),
physical vapor deposition (PVD), and thermal spray (TS). Both the initial equipment costs and the
operating costs for EP/ElsP coatings are relatively low. However, the by-products are considered highly
toxic and are subject to increasingly stricter government regulation, thereby making storage, reclamation,
and disposal major economic concerns. Thermal spray equipment, and therefore its cost, varies widely
from simple combustion devices to computer-controlled low-pressure plasma spray systems.
The operating costs are very much dependent on the cost of consumables such as powder, wire, or rod
materials as well as the quantities and types of gases used. Equipment costs for CVD are moderate, with
the understanding that neutralization of the output gases is an integral part of any system. The operating
costs of CVD are dominated by precursor gas costs and the frequent need to clean the systems. The cost
of PVD coating equipment is very high, due to the need to maintain high vacuums in chambers of
sufficient volume to make the process cost-effective. Operating costs are associated with the degree of
surface cleanliness necessary for coating adhesion, as well as the target costs.
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