Abstract:
In the construction field it is sometimes necessary to perform ultrasonic testing of a work piece
through paint or spray with various materials. This in theory is not allowed; a work piece needs to
be inspected prior to coating or after the coating is removed, which will affect the production
process. This research aims to study the effect of aluminum thermal spray coating on ultrasonic
testing by considering the effects of the signal amplitude attenuation and the velocity change of
ultrasonic waves. In addition, the accuracy of the location and sizing of the discontinuity on
aluminum coating if different thickness were assessed. The experiment was conducted with the low
carbon steel grade S420 applied with aluminum thermal spray coating thickness of 100, 200, 300,
400 and 500 microns. Test the integrity of the adhesion of the surface with aluminum by pull of test
method. For the ultrasonic testing, the longitudinal wave and surface wave were implemented by the
probe frequency 5 MHz and 2.25 MHz, respectively. Then, the echo height, attenuation and sound
velocity were measured. The experimental results inspected by ultrasonic testing on the surface of
aluminum thermal spray coating were found that, the echo height of using the longitudinal wave
with the probe frequency 5 MHz is decrease proportional to the thickness of the aluminum coating,
but the echo height obtained from probe frequency 2.25 MHz is opposite. That can effect to the
evaluation of decision making, accept or reject discontinuity, however, the sound velocity does not
affect to the position and sizing of the discontinuity. The benefits of this research is to know the
limitation and the effect of aluminum thermal spray coating on ultrasonic testing