Re: High temperature NDT ? Ultrasonics can be utilized with specialized high temp couplant. MT can be used but the issue of specialized consumables arises. PT is the simplest but again the need for a specialized penetrant and developer comes into play. It really depends on what type of cracks you're searching for... are they surface or sub-surface? 500 Celsius really isnt that hot. I've done examinations on considerably hotter surfaces. I believe the hottest was close to 900 celsius... though it was very difficult to get a reproduceable result... at that temperature minor fluctuations make huge differences on most UT sets. The set I found best for extreme high temperatures was the krautkramer USN58 series (L, K and I believe there's an N model too... my favorite is the L.... still use it today). hope some of this helps.