Monitoring of stress corrosion cracking in stainless steel weldments by acoustic and electrochemical measurements

Abstract

A new hybrid monitoring technique for chloride stress corrosion cracking (SCC) is proposed. It uses both the acoustic emission (AE) and corrosion potential fluctuation (CPF) techniques. This paper discusses the results of SCC tests on butt-welded Type 304 stainless steel pipes. The weld pipe suffered transgranular (TG)-SCC in a concentrated magnesium chloride solution (40 mass%), but suffered intergranular (IG) attack and falling-off of grains in a heat-affected zone (HAZ) in a dilute chloride solution (35 mass%). SCC initiations in both concentrated and dilute corrodants were successfully monitored using a CPF technique. However, the CPF technique could not monitor the propagation of the SCC. This propagation could be detected using an AE technique. Secondary AE was produced by hydrogen gas evolution and by the cracking of corrosion products, and the primary AE was produced by the falling-off of grains due to the mutual actions of anodic dissolution and the mechanical fracture along a chromium-depleted zone in the grain boundary. The volume of metal loss by the dissolution was predicted from the local anodic current due to the fluctuation of the corrosion potential, and was found to correspond to the volume of the grain boundary attack. The fact that the primary AE was detected just after rapid drop (RD)-type CPF suggested that the grain boundary corrosion caused the falling-off of the grain that produced the primary AE.

Analysis on spiral crack in thick diamond-like carbon film subjected to spherical contact loading

“…In this damage monitoring technique, the fracture process and the mode of the film fracture can be successfully revealed by a radiation pattern analysis of the Lamb wave AEs [36]. More recently, measurement of the corrosion potential fluctuation is also employed to detect film cracking, since the CPF is produced by the initiation of the localized corrosion [37,38] of substrate metal induced by local fracture of the film when the sample is immersed in a selected corrodant. The corrodant used in CPF is a solution which produces a non-Faradic reaction of the substrate metal, and when the film cracking occurs in a solution, local anodic current due to the anodic dissolution of the substrate metal is expected to produce a rapid drop of the corrosion potential to active potential.…”

Estimation of microstructural plastic property of die-cast Mg alloy (AZ91D) with an elevated temperature indentation

“…Such a computation procedure was carried out for both indenters in this study. Here it assumed that the hardening law of the β-phase is linear hardening law for simplicity, since the intermetallic compound is relatively hard and brittle nature (like ceramics material 4 [27][28][29]). The constitutive equation is in Eq.…”

Estimation of Stress Corrosion Cracking Initiation and Propagation in High-Pressure, High-Temperature Water Environment Utilizing Acoustic Emission

“…This limitation, however, can potentially be addressed by using acoustic emission (AE), which is a nondestructive technique that can use elastic waves produced by the emission of strain energy to detect SCC behavior in real time. Indeed, many researchers have reported that AE signals are produced by SCC initiation and propagation, 8,9) and that the event rate and amplitude these signals varies depending on the type of SCC. For example, tarnish rupture (TR)-type SCC tends to generate strong AE signals, 10) intergranular-type SCC (IG-SCC) generally produces weak primary AE signals, and transgranular-type SCC produces secondary AE signals and, in some cases, the loss of individual grains.…”

“…For example, tarnish rupture (TR)-type SCC tends to generate strong AE signals, 10) intergranular-type SCC (IG-SCC) generally produces weak primary AE signals, and transgranular-type SCC produces secondary AE signals and, in some cases, the loss of individual grains. 8) Monitoring these signals in high-temperature and high-pressure water environments, however, is made difficult by the low Curie temperature of the lead zirconate titanate (PZT) elements used in conventional AE sensors. There are some heat-resistant AE sensors currently available on the market, but these have a peak sensitivity that is lower than that of conventional AE sensors.…”