Nondestructive Evaluation of Long-Term Creep Damage and Its Availability in ASME Grade 91 Steel Welds

Abstract

In order to evaluate residual creep life of ASME Grade 91 weldment, Phased Array Ultrasonic Testing (PAUT), High Temperature Superconductor - direct current - Superconducting Quantum Interference Device (ECT・HTS-dc-SQUID), observation of replica and hardness measurement were used to detect creep damages for creep interrupted specimens. It was clarified that the threshold of the creep damage that PAUT and ECT・HTS-dc-SQUID could detect appear in later stage of creep deformation. Creep voids were detected on the replica obtained from surface of creep specimens just before creep rupture. Capacitive strain sensor, laser displacement meter and SPICA strain measurement were tried to detect creep strain. Creep curves by the capacitive strain sensor and laser displacement meter were similar with that of conventional extensometer with a linear gauge. Strain measured by SPICA in heat affected zone monotonously increased during creep. Strain measured by capacitive strain sensor, laser displacement meter and SPICA and damage detected by PAUT and ECT・HTS-dc-SQUID were assumed to be useful for residual creep life assessment.