H.R. Faridi - Department of Materials Science and Engineering, Hamadan University of Technology, Hamadan, Iran.
A. Momeni - Department of Materials Science and Engineering, Hamadan University of Technology, Hamadan, Iran.
M. Mohammadpour - Department of Materials Science and Engineering, Hamadan University of Technology, Hamadan, Iran.
V. Sarfarazi - Department of Mining Engineering, Hamadan University of Technology, Hamadan, Iran.

Two blade samples from the first and second stages of a gas turbine were investigated to understand the reason of fracture. All samples suffered excessive heat superficially. Using a TBC layer on top of Diffusion coating will be a reasonable solution for protecting the blades. Although in case of the first stage blades cracking was postponed, the thermomechanical fatigue cracks still originated from the blade surface. It was observed that the damage of the thermal barrier coating layer would lead to the overheating of the blades, promoting the rate of creep and rafting of g¢ precipitates. This phenomenon was more severe in the second stage samples with more damaged protective layers. It was found that the chemical composition of the fuel gas may increase the potential and rate of corrosion and damage to the blades. Concurrent with physical investigation, numerical simulation was performed to study the effect of particle impact into the blade. By changing the particle radii and its position, damage area was inspected. Numerical simulation shows that particle radii and its position have an important effect on the chipping removal from the blade.

Superalloys,  Precipitates, Thermomechanical Fatigue, Mercaptans, Numerical simulation