Laser ultrasound inspection for diffusion bonding
Project challenges
To eliminate the risk of contamination of bond surfaces, inspection of sealing welds prior to diffusion bonding must be performed using a non-contact and non-invasive inspection method, eliminating NDT methods such as fluorescent penetrant or contact ultrasound.
Business challenge
Product Innovation
Sector
Aerospace
Technology or capability
Metrology & NDT
Project Challenges
The project was posed by Rolls Royce. To eliminate the risk of contamination of bond surfaces, inspection of sealing welds prior to diffusion bonding must be performed using a non-contact and non-invasive inspection method, eliminating NDT methods such as fluorescent penetrant or contact ultrasound.
MTC's Solution
Laser Ultrasound Testing (LUT), being a non-contact and non-invasive ultrasound testing method, was selected to assess detection capabilities.
Calibration samples consisted of Ti64 welded plates which had Electric Discharge Machining (EDM) notches representing cracks that typically occur in the weld process.
A more representative geometry sample consisting of two Ti64 welded disks with EDM notches along the weld was also assessed.
All the deliverables for the work package regarding LUT of laser welds have been met and I am satisfied with the outcomes… Many thanks for all the excellent work you have carried out over the last 5 months.
John H. Boswell - Rolls-Royce
The Outcome
- The MTC’s LUT system showed good capability to detect notches along the weld and even some of unintended notches orientated across the weld.
- Where the smallest detected notch along the weld had dimensions of 0.46x0.25x0.14 mm.
- It also showed good detection capability on the welded disk where the smallest detected notch dimensions were 0.45x0.26x0.13 mm.
Benefits to the Client
- A non-contact non-invasive inspection method has shown good capability to detect defects that typically occur in diffusion bonding pre-welding.
- LUT showed good capability to detect defects that typically occur in diffusion bonding pre-welding in both plates and welded cylinders, detecting notches as small as 130 µm in width.
- Data processing such as filtering, normalisation and optical compensation were explored, but raw data was enough to show indications corresponding to intended defects (notches).
