DETERMINATION OF THE CREEP PROPERTIES OF CREEP RESISTANT MARTENSITIC STEELS AT ELEVATED TEMPERATURES FROM THEIR CRACK OPENING DISPLACEMENTS (COD)

摘要

In the 21st Century, the world faces the critical challenge of providing abundant, cheap electricity to meet the needs of a growing global population, while at the same time, preserving environmental values. Due to this type of challenge, many studies were focused on the assessment of the creep properties of steels used in power generation industry around the world. This paper studies the possibility of using the crack opening displacement (COD) values to estimate the creep properties of creep resistant martensitic steels. The criterion of (COD) may be applied to estimate both the strength for 1% creep strain, and creep rupture strength of creep resistant martensitic steels at elevated temperatures. The COD value could be determined by applying tensile tests at elevated temperature for a group of samples that are prepared with different radii of notch. Individual relationships between the COD and both of these creep properties at 500℃ for the investigated steels were introduced. Due to the longer time needed for the application of the well known conventional practical methods for measuring the creep properties of steels, such as 1 % creep strain at 500℃ for 10{sup}5 hours (more than 10 years) and the higher cost needed for these measurements, the authors have found that these relationships can be used as an assessment of creep properties of the investigated steels in shorter time and less cost. The other suggestion of the authors is to use the resulted relationships for comparison of the creep properties between base metal, weld metal and heat affected zone (HAZ) for welded joint of creep resistant martensitic steels.