Study on Grain Boundary Sensitization in Heat Affected Zone of Austenitic Stainless Steel and its Evaluation Method

Abstract

In this paper, the simulated welding structure at different areas of heat affected zone (HAZ) of austenitic stainless steel are prepared by heating furnace, and the deference of intergranular corrosion resistance of all samples were determined by comparative methods of oxalic acid etching, hot-acid test and electrochemical potentiodynamic reactivation tests (EPR), and the effectiveness of all those methods were analysis and determination at the same time. The result shows that the susceptibility degree at different areas of HAZ increased with the heating temperature increase, but all structures can pass hot-acid test and EPR test, indicating that it could maintain good performance of intergranular corrosion resistance. The hot-acid test results have good consistency with EPR test , but inconsistent with oxalic acid etching test. The results show that the evaluation of oxalic acid etching is too much strict to be used as a judgment method, so that not suitable of use for inspection.

Microstructural Evolution and Mechanical Performance of Two Joints of Medium-Mn Stainless Steel with Low- and High-Alloyed Steels

“…It was reported that the precipitation of carbide particles on the grain boundaries has pinning effects on the grain growth [ 54 , 55 , 56 ]. Therefore, the precipitated carbides in the TZ work as obstacles for the movement of the grain boundaries, which hinders the coarsening of the grains size at the TZ and works as heterogeneous nucleation sites, which enhances the formation of fine equiaxed structures in the TZ; therefore, the size of the grains at the TZ was finer than the grains which exist at the FB and CGHAZ, which is similar to the results presented in the literature [ 52 , 57 , 58 ].…”

“…The main reason behind the appearance of the TZ is the sensitization effect [ 50 , 51 , 52 ]. The sensitization takes place in the HAZ region at a temperature range of 400 to 800 °C after the welding of austenitic steels.…”

Improved Ability to Resist Corrosion of Selective-Laser-Melted Stainless Steel Based on Microstructure and Passivation Film Characteristics

“…During the reverse scanning process, corrosion damage occurred due to incomplete passivation during the forward scanning process, which revealed the formation of chromium carbide precipitates near the grain boundaries of the steel materials [36]. In addition, the I r value revealed in the DL-EPR experiment that the material was passivated due to the consumption of Cr element, resulting in a lower value of I r than the value of I a [37].…”

“…The I p value of the forging 304 steel increased from 2.565 µA cm −2 (forging sample) to 7.462 µA cm −2 (forging + ST sample) after the sensitization; the ∆E value decreased from 0.341 V SCE (forging sample) to 0.334 V SCE (forging + ST sample). The I p and ∆E values can represent the characteristics of the passivation films of metals [17,37,38]. Generally, the smaller the I p value or the higher the ∆E value of steel materials, the slower the corrosion rate and the better the quality of the passivation film on the material.…”