Co-operative Research projects for SMEs - European Commission ...

Process stability is key to coating quality
“This approach will provide a simple,
The application of thermal coatings is a well-
economic, robust solution.”
established industrial practice and the performance of
any coating depends to a large extent on its quality. While the
quality of both the materials and the process can be quantified and
assured, stability throughout the sometimes lengthy spraying processes
required for particular products can be difficult and expensive to monitor. The Desire
Co-operative Research project aims to provide a simple, effective, robust and economical
system for SMEs in this field to use and manufacture. The participants will ensure that existing technology
can be transferred, adapted and tested to meet the specific requirements of the industry.
Thermal coatings are used to provide protective surfaces that
extend the life of components operating in hostile environments, such
as aerospace turbine engines subjected to high temperatures,
prosthetic devices implanted in the body, and oil and gas rig components
that have to withstand erosion, corrosion and abrasion.
These coatings offer resistance to wear, corrosion, and heat, as well
as creating surfaces with specific characteristics like electrical conductivity.
Thermal spraying produces a continuous coating by melting
or softening the coating material into droplets then projecting
it on to the substrate at high velocity. The processes currently in use
include Low Pressure Plasma Spraying (LPPS), High Velocity Oxy
Fuel Spraying (HVOF) and Arc Plasma Spraying (APS) amongst others.
The parameters controlling the quality of the end result concern
the spray gun, the material feed, the spray stream (plasma or
flame), and the substrate.
In order to compete economically and meet the industry’s stringent
quality demands, SMEs need a cheap, robust and reliable means
of guaranteeing the stability of the coating process. To achieve this,
the Co-operative Research project – Development of Simple and
Reliable on-line Monitoring Equipment for Thermal Spraying Control
(Desire) – has been set up. SMEs engaged in the application of coatings
and the manufacture of coating equipment, along with a technology
transfer institute, are collaborating with university researchers
who are investigating how technologies not previously employed
in this field can be adapted to address current industrial specifications.
Suitable systems
Coating performance is largely dependent upon its quality, so the
provision of high-quality coatings is a priority for all thermal spray
companies. Advanced control systems are available to monitor and
control the primary input parameters, thereby ensuring reproducible
conditions. However, such systems do not present a comprehensive
control system, nor are they particularly well-suited for
small and medium-sized enterprises (SMEs). Measurement of physical
parameters – such as the velocity, and temperature of the
powder particles – requires complex instrumentation, making the
systems expensive and complicated to use. More importantly, they
are ineffective at monitoring the stability of the spray process, and
high-quality applications require processes that take four to six hours
DESIRE
of continuous spraying to complete. Changes due to damage or wear
in the nozzle, problems in the feed lines, or gas leaks, all of which
have a crucial impact on the quality of the finish, may remain
undetected.
In current procedures, maintaining the procedure’s stability comes
down mainly to the operator’s powers of observation and experience.
This is difficult and impractical to maintain during a long spraying
process, as is ensuring consistency over the weeks and months
that the spraying equipment may be in use. So, the Desire project
will aim to develop a reliable, simple, cost-effective, and robust control
system that can be integrated easily into existing spray cells to
monitor the stability of the procedure.
Quality performers
The participants in the project team will cover all aspects of the system’s
development, from research through to testing then manufacture.
The Inasmet foundation in Spain, acting as project coordinator,
is involved in technology transfer. Italy’s University of Firenze
is responsible for the initial development of a lab-scale prototype
of the system which will be tested by three thermal spraying SMEs
in Germany, Italy and the UK. Between them, these companies cover
an extensive range of processes and products including those
exacting the most stringent quality requirements, such as turbines
and aeronautical components. They will
calibrate and evaluate the
performance of the prototype
in different
applications. An
Italian company,
Artec, which
manufactures
Thermal coatings
offer resistance to wear,
corrosion, and heat.
© Airbus