Material creep
This is a didactic model that illustrates trends. Actual assessment of pressure parts, boilers and piping requires material creep data, code-based calculations, operating history and weld inspection.
Open interactive module →Topic overview
This is a didactic model that illustrates trends. Actual assessment of pressure parts, boilers and piping requires material creep data, code-based calculations, operating history and weld inspection.
Creep becomes technically significant at approximately 0.3–0.4 Tm. The same temperature of 550 °C therefore represents a completely different condition for aluminium, ferritic steel and a nickel alloy.
In Cr-Mo and 9–12% Cr steels, the decisive region is often not the weld metal but the softened fine-grained/intercritical HAZ. Creep strain concentrates there and intergranular damage develops.
Material, heat input, interpass temperature, preheat, PWHT, filler material, HAZ hardness, NDT and the periodic inspection plan. A creep assessment is incomplete without service time and temperature.
What the module covers
- Material creep — long-term time-dependent deformation
- Interactive creep estimate
- Homologous temperature
- Primary, secondary and tertiary creep
- Type IV cracking
- What the welding engineer must address
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