A common failure mode is inadequate tempering during PWHT, which leaves a hard, untempered martensite in the heat-affected zone (HAZ). This microstructure reduces creep life and increases the risk of Type IV cracking in the intercritical HAZ during service.
Key PWHT parameters that must be verified through thermal cycle documentation:
• Heating rate: ≤200°C/h for thicknesses up to 50 mm, slower for thicker sections.
• Soaking temperature: within ±10°C of the specified range.
• Cooling rate: controlled to avoid residual stress and re-hardening.
Auditors typically check the PWHT chart for temperature uniformity and time-at-temperature compliance. A deviation of even 15°C can shorten creep life by 30%.
How does your team validate PWHT cycles for creep-resistant steels?
Source: EN 10028-2, 2017