MCrAlY bend test

[sal]

Hi guys,
I have a quality control problem.
I have sprayed MCrAlY (Amdry 365-1) for a customer and he made bend test to check adhesion strength, but the coating cracks and spalls off and he won't accept it.
I know that MCrAlYs coating are brittle before heat treatment and I was wondering if there is any standard or documents to show that this test is not the right one for adhesion before heat treatment.
Any help and info is appreciated.
Regards,
Sal

[djewell]

Bend tests are usually done on thin coatings. Of course a thick coating like you showed is going to crack and spall. A coating is not as strong as the substrate, so it will not handle stresses like cast metal coupons.

Bond strength testing is done according to ASTM C 633-1, and it produces a quantifiable result. It measures the adhesion of the coating to the substrate. A bend test does not produce a quantifiable measurement. In my opinion, it is more of an evaluation of the cohesion of the particles to each other.