Boronizing Mitigate Failure Mechanisms With Extended Life in Oil/Gas Steel Piping Under Acoustic Induced Vibration (Aiv)

Abstract

Oil and gas piping systems suffer from acoustically induced vibration, AIV, that end with hearing losses and consuming personnel's lives. However, Leak-Before-Break (LBB) methodology was developed to mitigate failure, the primary piping systems exhibit an extremely low probability of rupture (xLPR). For understanding of piping failure mechanisms under AIV, 3-point bending tests are conducted to study structural integrity in oil/gas piping (ASTM A333 Carbon Steel GR.6 Seamless). Besides, for ultra-fast surface hardening and strengthening, a non-traditional powder pack boronizing technique is introduced at 950 o C for 10 and 30 minutes. Mechanical characterization as well as microstructural analysis are conducted for continuous and incremental bending tests. In addition, FE modeling, ANSYS, is conducted on actual "case study" of oil/gas piping to study the changes in dynamic characteristics for both as-received (AR) and boronized steel Under AIV(173 dB). Failure mechanisms is established in AR sample with clear banding and early localized microplasticity at 0.2 flexural stress (f). Void coalescence induce crack initiation at 0.3 f. Crack propagation (at 0.5f), crack evolution (at 0.7f) and catastrophic failure are captured. Boronizing with the diffusion of Boron into the outer surface dominate functional-graded materials (FGM), with surface and bulk hardening. Surface hardening via boronizing mitigate fracture mechanisms with no clear micro-plasticity, but with clear twinning and banding elimination. In addition, to investigate the sustainability of piping and the effect of boronizing, under AIV, FE modeling is introduced with two different steel piping systems (AR with strength 580 MPa, and boronized steel with strength 1390 MPa). Failure mitigation is introduced with the increase of endurance limit as well as increase of piping life.