4 Material Transformations Revealed by High-Temperature Fatigue Tests

high-temperature-tensile test-croppedExtreme temperatures in a product's operating environment affects the fatigue life of many materials. With the same cyclic or repeated stress or strain loading conditions, a material's characteristics could vary significantly at different temperatures. These conditions could be a low, moderate, or high temperatures. Cyclic loading may or may not be associated with cyclic temperature fluctuations.

A specialized high-temperature fatigue test frame's ability to expose the test specimen to temperatures up to 1800°F can replicate the operating conditions experienced by turbine blades in gas engines, power generating plants and jet engines.

The effect of a high temperature operations or exposure on mechanical properties of these parts or products can be linked with changes in the base material's structure.

Four of the transformative states created by elevated temperatures are:

  • Diffusion processes- a liquid, a gas, or another solid can mix together with the host solid on the atomic level.1
  • Aging - elevating the temperature of the solution heat-treated metal alloy to a point below its recrystallization temperature but high enough to speed up precipitate formation.2
  • Dislocation restructuring (softening) - The movement of dislocations allow atoms to slide over each other at low stress levels and is known as glide or slip, primarily in plastics.3
  • Recrystallization- deformed grains are replaced by a new set of defect-free grains that nucleate and grow until the original grains have been entirely consumed.4

In addition, elevated heat creates thermal stresses and presents a major impact on pitting, micro-pitting, scuffing, and wear on the surface – reducing the fatigue life of the material. A comprehensive high-temperature fatigue testing program can help identify favorable material characteristics for the end products planned operating environment.

Learn more about  IMR Test Labs high-temperature fatigue testing capabilities.

1) Springer Link
2) MetalSupermarkets.com
3) Wikipedia
4) Wikipedia