Impact of temperature changes on the microstructure and mechanical characteristics of AISI 304 submerged in 5% HCl...

This study aims to evaluate the behavior of stainless steel 304 grade after immersion into corrosive environments of 5% HCl solution. The initial temperature of four steel plates was selected as room temperature, 50 °C, 80 °C and 110 °C. One plate was considered in 'as received' condition. To evaluate the various mechanical properties of the metal under immersion in HCl solution, various tests were performed such as tensile test, bending test, hardness test, microstructural analysis, and XRD which were compared with the same properties of untreated piece of metal. There is a significant difference between the microstructure of 'untreated' sample and four 'solution immersed' samples. The observations like grain boundaries widening, increment in M₂₃C₆ contents, pitting and cavities primarily at γ boundaries are indicating the occurrence of corrosion in the samples. The tensile and yield strength of 'as received' specimen was noted as 680 MPa and 326 MPa respectively. The immersed specimens showed no significant variation in tensile strength, despite the fact that the maximum bending force was reduced to produce a large deflection in the 'solution immersed' plates during the bending test. Due to corrosion, hardness values are not constant throughout the plates. It may somewhere harder due to Cr embrittlement. A preferential attack on ferrite content was observed on the solution immersed samples and therefore a higher concentration of the more corrosion-resistant austenitic phase was seen in XRD analysis.