Transcript NDT of HVOF Coatings

NDT of HVOF Coatings
John Sauer
Sauer Engineering
HCAT Toronto
September 25th, 2002
NDT
• Outline
–Where have we been??
–Where are we going??
NDT
• Where have we been?
Chrome plating
– Common usage of magnetic particle and
fluorescent penetrant
– Recent inclusion of Barkhausen
inspection on critical components
– Some applications require stripping of
chrome regardless of condition-no NDT
issues
NDT
• What are we looking for??
– Chrome is already cracked so we are not
looking for “plating defects”
– Looking for substrate defects or
“grinding burn” via Barkhausen
NDT
• What do we see??
– Recent studies by AFRL and Boeing
St.Louis say that any defects under .250”
( that size may be larger) cannot be found
with common methods
– Barkhausen can detect burn but cracks??
NDT
• Hill AFB
– Estimate that ~ 50 % of the parts that
come in for repair with chrome are not
stripped and put back into service
– Question
• Are .250” defects OK from a damage
tolerance standpoint??
• What size defect do we really need to find??
NDT
• Where are we going??
HVOF Coatings
– A positive aspect of HVOF is the
possibility that the coating may not
require stripping thru multiple repair
cycles
– However, this highlights the issue:
• What is happening in and under the
coating??
NDT
• What are we looking for??
– Cracks/defects in coating
– Delaminations
– Substrate cracks/defects
• Size of substrate defects
– Must be in the .250” critical size range
since we must be better or EQUAL to
chrome 
NDT
• What do we see??
– Limited work shows varied forms of
ultrasonic are the “best methods for
seeing smaller defects down to ~.050”
NDT
• How do we get there??
– Define the requirements
– Understand the applications
– Assess production feasibility
NDT
What are we looking for??
– Size
– Location
• How does that vary from application to
application?
• What is the production feasibility for use
of the technique on a reliable basis in the
field?
NDT
• Research has shown some ideas on the horizon
might be:
– JENTEK's MWMTM-Array sensor to
involving eddy-current technology
– EWI suggests either eddy current or USI C scan
– GEAE suggests Pulsed Eddy Current (PEC)
– Naval Center has performed work on corrosion
under paints using
• Real time Ultrasound Imaging
• Thermal Imaging
• Near Field Microwave Imaging
NDT
• JENTEK's MWMTM-Array sensor
technology can be used to develop surfacemountable eddy-current sensors that can be
modified for difficult-to-access locations
on complex configurations
• Work has been performed on coatings for
Gas Turbine Industry and WCCo
NDT
• Ultrasonic inspection by EWI (similar to
AFRL)
Ultrasonic C-Scan Image of a Coated Sample
NDT
• GEAE suggests Pulsed Eddy Current (PEC)
– Most existing Eddy current inspections use single
frequency excitation
– Uses a current pulse in a drive coil to transmit
transient electromagnetic flux into the structure
– Advantages of this are the presence of wide range of
frequency components in the exciting field
– Work would be performed by GE's Global Research
Center (GRC)
NDT
• Naval Center has performed work with on
corrosion under paints using
– Real time Ultrasound Imaging
• Basis is patented two dimensional piezo microelectric array
to generate real time C-scan
– Thermal Imaging
• Active Thermography-External source for heat -use IR
camera
• Sonic Thermography-high amplitude sonic waves cause
frictional heat-use IR camera
– Near Field Microwave Imaging
• Rely on rlection properties of metallic surfaces using open
ended microwave probes
NDT
• Cannot resolve this issue today
• Significant issue for both HCAT/PEWG
• Subcommittee being formed with Chuck
Alford(PEWG) and John Sauer (HCAT) as
co-chairs to pool resources and address
issue
NDT
• Any one interested please see Chuck or
myself during this meeting
• Possible side discussion tonite if people are
interested