CREEP RESISTANCE OF WELD JOINT OF TUBE MADE OF P92 STEEL

One-side weld joint of W type was prepared from P92 type steel using GTAW & SMAW method. Creep testing of smooth cross-weld samples at temperatures ranging from 575 to 650 degrees C and at stresses from 70 to 240 MPa was carried out. Ruptured samples were undergone fractographic analysis and extended metallographic investigation including scanning and transmission electron microscopy. After creep tests at temperatures above 575 degrees C increase in size of secondary phases and cavities formation were evident. Voids were concentrated in fine prior austenite grain heat affected zones. In addition, sporadic occurrence of individual cavities was found out in the base material and the weld metal after tests at 625 and 650 degrees C. During creep exposures at temperatures above 600 degrees C Laves phase precipitated and their particles grew. Critical zone from the point of view of the creep failure is located in the fine prior austenite grain heat affected zone and in the overheated zone of the base material.