The Synergistic Effects of Boron and Impression Creep Testing during Paced Controlling of Temperature for P91 Steels

Abstract

This article induces the quadruple knowledge on effects of 100 ppm (P91B) and 22 ppm (P91) boron in as‐received 9Cr steels in normalized and tempered conditions (NT) and impression crept conditions (ICC). Herein, impression creep testing is improved through paced temperature to fast evaluate creep performance. P91B performs the utmost by advancing activation energy and 30% better creep life, leading to same targeted creep life to 574 °C than P91 at 550 °C. Further, it incisively discusses variations in microstructure, precipitate size, geometrically necessary dislocations (GNDs), pseudo‐rocking curve, grain size (GS), several types of grain boundaries (GBs), effective GB energy, and elastic stiffness. Novel phenomenological mechanisms like GB hardening/softening; antithetical mechanisms; boron‐dependent mosaicity; grain refinement/fragmentation/coarsening/homogenization; interaction among various types of GBs, triggering re/degeneration of dislocations and Σ boundaries as Σ reactions; super‐continuous and geometric dynamic recrystallizations; enhanced creep immunity of like‐oriented GBs than unlike oriented GBs; primary/secondary recrystallization; specialness; boron/NT/ICC‐dependent stiffness; high stiffness is dependent on low GNDs and big GS, and vice versa are observed. The synergistic effects of [100 ppm boron in NT/ICC] and ICC in manifestation of 22/100 ppm boron are ascertained. However, dependency [proportionally and antithetically] and independency of GB character on creep‐microstructural reciprocity discourse and converse into the mathematical relationship.