Abstract
Intergranular corrosion of commercial stainless steel type X6CrNiTi18-10 (1.4541, AISI 321) is frequently observed in several process environments. These localized attacks are normally attributed to the carbide precipitation and concomitant depletion of chromium near grain boundary due to steel exposure to sensitization temperature. Such undesirable microchemistry is expected to be changed further if the material undergoes deformation prior to sensitization. Present paper deals with the influence of a wide range of cold rolling (5, 10, 15 and maximum 40% cold deformation) and the sensitization time (aging at 700°C for 0.12, 0.5, 1, 4, 16 and 32 hours) on intergranular corrosion (IGC). The assessment of the degree of intergranular corrosion was based on the measurement of mass loss and observation of corroded surfaces on optical microscope. The consequences of deformation on IGC have been investigated by using EN ISO 3651-1methods (Huey test). Cold deformation before sensitization reduces the intensity of intergranular corrosion of this steel. The deformed structure created during the cold work process, numerous slip planes and the twins boundaries are just like the grain boundaries and the places where the chromium carbides preferentially precipitates.
Highlights
The stainless alloy X6CrNiTi18-10 (1.4541, AISI 321) is a general purpose austenitic stainless steel with a face centred cubic structure
Stainless steels are common material of construction as these offer a wide range of corrosion resistance along with good fabrication and mechanical properties to many industrial environments. These alloys are prone to microstructural changes along with changes in chemistry when exposed to sensitization temperatures possibly due to faulty heat treatment or welding operation
The present paper reports the results of various deformation levels on intergranular corrosion (IGC) and the attempt has been made to establish the correlation of corrosion rates with sensitization time and microstructure
Summary
The stainless alloy X6CrNiTi18-10 (1.4541, AISI 321) is a general purpose austenitic stainless steel with a face centred cubic structure. The well‐known susceptibility of austenitic stainless steels to intergranular corrosion after heat‐treatment in the temperature range of 500°–800°C (sensitization) has long been attributed to depletion of Cr from regions of the alloy matrix adjacent to grain boundaries in which Cr23C6 had precipitated. Those regions of the steel in which the local Cr composition falls below about 12% have a diminished ability to form a passive film and corrode preferentially [4] (Fig. 1). The present paper reports the results of various deformation levels on IGC and the attempt has been made to establish the correlation of corrosion rates with sensitization time and microstructure
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