Here we have a good example of the effects of overheating on a T04Z. As seen in the photos, the turbine shaft has been subjected to  excessive heat, causing it to warp. The effect of this excessive heat was made worse as the turbine housing was also warped causing contact between the turbine vanes and turbine housing venturi. It is also apparent  a foreign object has been through the turbine damaging the vane tips furthermore. Three main causes for overheating are excess exhaust gas temperatures (EGT), lack of oil cooling and coolant vaporization in the bearing body.