Magnetic Property Evaluation of Creep Damaged Cr-Mo Steel Components used in Power Plants
Magnetic properties of steel are sensitive to the total volume of magnetic inclusions in the material . These magnetic inclusions may be precipitates or microscopic voids. When a material is subjected to an elevated temperature under stress for extended periods, slow plastic flow of material occurs which eventually leads to microscopic voids, cavities and finally macroscopic cracking. This process is known as creep damaged. Depending on the strain rate within the material, the creep process can be divided into three categories. In the early stage of the creep process known as primary creep, the material deforms rapidly with time. But this strain rate gradually decreases and becomes independent of time. This stage of creep process is known as secondary, or steady state, creep. In the final stage which is known as tertiary creep, the strain rate again increases with time and deformation continues until the material fails.