Creep performance of steels for challenging applications

Increasing thermal loads, temperatures and pressures can be attractive to improve the efficiency and operational economy of power and process plants. With increasingly variable supply from renewable sources, however, thick-wall components and their materials like steels that may perform well under steady loads at high temperatures and pressures can be significantly challenged by the new regime of service. In addition, in high temperature plant the issue can arise also in the creep dominated base load case, when higher strength structural material is selected to limit section size, but other material and weldment properties intervene with complications from reduced creep ductility, unfavourable weld behaviour or less than optimal thermal properties. In this paper, we compare conventional and newer low and high alloy creep resistant steels in terms of expected and observed material properties and suitability for the changing modes of operation. Examples include the experience and suggested limitations in power plant application with e.g. welded T/P23 and T/P24 in comparison with conventional low alloy steels, and with newer and conventional austenitic steels