Transcript NDT of HVOF Coatings
Documentation/Implementation Issues with HVOF Coatings
John Sauer Sauer Engineering HCAT San Diego April 1st, 2003
Documentation/Implementation
• Outline –Documentation of deposition/process parameters in spraying –NDT evaluation status
Documentation
• HCAT community has grown substantially • Moving into a critical phase for implementation
Documentation
• Documentation of process parameters therefore more critical than ever – More players-less control (Jerry) – May have companies, personnel, or locations with less experience
Documentation
• From this point forward, there will be a standard format required for spraying of specimens under the HCAT banner • Memo will be issued and available on the website
Documentation
• General process/console parameters • More critical issue like movement across part, cooling air locations, photographic documentation
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Documentation
Attachment 1
Coating Process Control Sheet
GENERAL INFORMATION:
PROCESSOR: Thermal Spray Shop ABC COATING SPECIFICATION: Current HCAT Requirements PURCHASER: HCAT Landing Gear Protocol PART NAME: HCAT Fatigue Specimens PART NUMBER .25 inch dia. Hourglass and Smooth Fatigue Bars BASIC MATERIAL: 4340 Rc 52-55 COATING MATERIAL: WCCo Dimalloy 2005 LOT/BATCH NO: ABC 10234
SURFACE PREPARATION:
PRE-BLAST CLEANING: Acetone dip for degreasing BLASTING GRIT TYPE: Aluminum Oxide GRIT SIZE: 54 grit PRESSURE: 40 psi air presure STAND-OFF DISTANCE 6-8 inches ANGLE OF BLAST 45 degree angle SURFACE FINISH 100 to 150 Ra
SPRAY EQUIPMENT & ACCESSORY EQUIPMENT:
MANUFACTURER: Sulzer Metco TORCH: DJ 2600__ POWDER PORT: N/A HEAD: Standard NOZZLE: Standard__
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Documentation
WORK HANDLING:
PART MOTION: Rotation SPEED: 1835 inches/min (2636 rpm)
Rotation
2636 rpm
Traverse
400 in/min GUN MOTION: Linear SPEED: 400 inches/min___ GUN-TO-WORK DISTANCE : 11.5 inches ANGLE: 90 degrees__ SPRAY MASKING/FIXTURES: Hard shadow masking__ Make 5 full coating passes along the length return to top and allow 20 sec pause for cooling
QUALITY CONTROL DATA
MICROSTRUCTURE: < 1.5% porosity HARDNESS: 1020 Vickers (300 gram)__ BOND STRENGTH: 11, 500 psi BEND TEST: No cracking or spalling___ ALMEN TESTING: .007 -.009 compressive SURFACE FINISH: 100 Ra (as sprayed)__ 5 Ra (finish grinding)__ ACTUAL MAX PART TEMP: 325 degrees F It is important to understand that this is an example only. The data for a specific spray system and set-up may require some different information and the form content may need modification. The intent is to document how the parts are sprayed so that the set-up can be re created.
Documentation
Documentation
• Four critical points – Need for trouble shooting – Need for consistency – Not a new policy – Not company approval or approval of your process
NDT
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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
chrome to
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?
Current NDT Status
• Pratt/Tinker – Parts are not fatigue critical-no worry!!
• Hill – Current FPI/MPI methods are acceptable • Identifying new method not critical at this time
Current NDT Status
• Must continue to “consider” but no “driving” force now • Will monitor current methods/research in industry • More concentration on issues if implementation issues are identified
Current NDT Status
• Contact – John Sauer Sauer Engineering – Chuck Alford PEWG
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 surface mountable 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
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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