Which is the first stage of blade creep?

• A. Primary
• B. Secondary
• C. Tertiary
• D. Quaternary

Answer: (A)

Primary creep is the first stage of blade creep. In this phase, the deformation rate is high at the start and then slows down as the material work-hardens and its microstructure begins to impede dislocation motion. This transient decrease in creep rate is typical as the alloy responds to the applied high temperature and stress. After this initial period, secondary creep sets in with a near-constant rate as recovery processes balance hardening, and tertiary creep follows with accelerating damage leading toward failure. Quaternary creep isn’t part of the standard three-stage model for turbine blade creep.