Examination of component surfaces, using special equipment
such as Borescopes, and magnifying glasses.
The application of a coloured or fluorescent
dye to detect surface breaking defects on
Detection of flaws on or just underneath the surface of
ferromagnetic materials, using fluorescent, black, or dry
(yolk) DC or
This method uses the transmission of high-frequency
sound waves through a material to detect internal
defects. The pulse-echo method is the most commonly
used ultrasonic testing technique. Automated and
advanced ultrasonic testing methods, such as phased
array and time of flight diffraction, are also used.
This technique generates eddy currents up to a few millimeters below the
surface of a conductive material through an induced alternating magnetic
Material defects will disturb the flow of eddy currents and generate a
Replication is used to evaluate microstructures and
other surface features.
Radiography uses an x-ray device or radioactive isotope as a source of
radiation which passes through the material and is captured on film or digital
After processing the film an image of varying density is obtained. Possible
imperfections are identified through density changes.
One of many advantages of cast steel for complex designed structures such as
turbine components is, that defects can be repaired by welding .
A large variety of NDT methods are available for the condition
assessment of gas turbine components.
Selecting the most appropriate one depends upon:
The type of component
The type of defect
The specific situation, such as the accessibility or cleanliness of the part
Images for surfaces of gas turbine blades made of the ŻS6-K alloy, ordered
according to the criterion of the increasing degree of the material overheating
Józef BŁACHNIO : EXAMINATION OF CHANGES IN MICROSTRUCTURE OF TURBINE
VANES WITH THE USE OF NON-DESTRUCTIVE METHODS