An industrial gas turbine operator found evidence of turbine blade in-service degradation which in at least one case was ascribed to the loss of a first stage blade tip. Four turbine blades of 120,000 hours service were forwarded to TWI for investigation.
- Determine if damaging degradation was present
- Recommend remedial action to address any degradation found
- Detailed visual examination using binocular microscope and fluorescent penetrant
- Chemical analysis and X-ray mapping of blade material
- Tensile testing
- Metallographic inspection
- Confirmation that the material quality was acceptable
- Confirmation of no significant degradation so no remedial action on components recommended
- A review of operating environment recommended
The blades supplied for investigation showed no significant degradation thus no remedial action recommendation was made. The blades were within specification and had not suffered significant hot corrosion. A recommendation to analyse the fuel gas was made to determine if a change in operating environment had contributed to blade degradation. Although not required for this investigation, creep rupture testing would have determined the blades' fitness for further service.