Severe operating conditions in terms of high speed with heavy braking loads and elevated temperature gradients
together with continued environmental exposure can affect the operability and the performance of
wrought and cast brake discs of automotive vehicles such as passenger cars [1–5], trucks [6], motorcycles
[7], etc., causing their failure by thermal fatigue. These situations often occur in considering fire fighting motor
vehicles used in supporting to the flight activities that must operate in very short time at high speed, i.e. less
than 2 min and about 100 m/s, respectively During NDT controls, a conspicuous number of brake discs of IVECO-DRAGON X6 fire fighting motor
vehicles used in aeronautical grounds and made of a pearlitic gray iron with type A graphite flakes, were found
cracked. In particular, the cracks had initiated at a very early stage of the brake application in the radial direction
of the friction surfaces. Their length was approximately in the interval 1–7.5 cm and the deepest ones were
also found on the external rim surfaces at the edge of the cooling holes.