THE EFFECT OF WELDING ON THE PROPERTIES OF NEW AUSTENITIC STEELS FOR USE IN BOILERS WITH HIGHER STEAM PARAMETERS

The project MPO FR-TI3/458 "Material solutions for industrial equipment working with ultra-preheated steam", is focused on the assessment and prediction of long-term creep life of heterogeneous and homogeneous weld joints of the selected materials that can be used for superheaters and re-heaters of newly built or refurbished power plant boilers. The acquisition of detailed and reliable information, especially about the behaviour of weld joints exposed to high temperatures and pressure during long-term operation is of vital importance. Examined heterogeneous and homogeneous weld joints were made from austenitic heat resistant steels HR3C, SUPER 304H and Tp347HFG and also from martensitic steel P92. In order to ensure optimal and reproducible welding conditions, it was necessary to set the parameters of automated orbital GTAW welding, including thermal regime during welding - preheating, interpass and reheating temperatures as well as postweld heat treatment (PWHT). Information about the properties and behaviour of the welds were obtained by testing (WPQR) made in compliance with standard EN 15614-1. The presented work thus builds on the results of previous activities published last year and now it presents the results of welds and tests performed on heterogeneous weld joint of steels Tp347 HFG and Super 304H. Besides the principal results it shows also the results of additional testing of materials made after different regime of PWHT. Moreover, we present the preliminary results of long-term creep tests, which are still continuing.