Effect of groove angle on creep rupture and damage behaviour of P91 steel weld joint

Creep studies on the v-groove (angles of 70° and 90°) and square butt weld joints of P91 steel fabricated by tungsten inert gas (TIG) and activated-TIG (A-TIG) welding techniques have been carried out at 923 K and 60–100 MPa stress. M23C6 precipitates were coarser in the inter-critical heat affected zone (ICHAZ) (118 to 190 ± 20 nm) than the other regions (90 to 140 ± 20 nm) in the joint. The extent of coarsening of M23C6 precipitates in the ICHAZ of the weld joint has increased from 118 to 190 ± 20 nm with an increase in groove angle due to an increased number of weld thermal cycles. Creep deformation rate was lower in the weld joint with lower groove angle. At lower applied stress, the 70° weld joint has shown higher creep rupture life (tr) by a factor of 1.6 than the 90° weld joint. However, A-TIG (0°) weld joint has exhibited higher tr by a factor of 2.5 than the 70° weld joint. Overall, the creep rupture life of the welded components of this steel can be considerably improved by designing the weld joint with a lower groove angle.