The corrosion behavior of WEDM machined stainless steels in a pyrolysis environment

Abstract

Pyrolysis represents one of the most convenient technologies for the chemical transformation of waste. The exposure to corrosion products and high temperatures does, however, require chemically resistant construction materials. This study was carried out to analyze the corrosion behavior of 1.4571 (AISI 316Ti) and 1.4305 (AISI 303) stainless steels machined with wire electric discharge machining (WEDM) in a pyrolysis environment. Different machining parameters were used for both materials tested to examine the influence of WEDM machining. The total testing time in the pyrolysis environment was 28 days, with the testing chamber being refilled 12 times. The surface topography was analyzed following the WEDM, cleaning, and corrosion test. The surface morphology and cross-section analyses were carried out using electron microscopy at all three stages of the process. An analysis of the chemical composition of the surfaces was carried out as well as of the pyrolysis environment to which the samples were exposed. It was established that the organic acids found in the pyrolysis chamber did not degrade the tested stainless steels to a meaningful degree. Minor fissures, that is, fine precipitated carbides, were observed on the surface of both the steel types and in their subsurface layer, as well as a significant presence of carbon. This presence was directly connected to the impurities found on the surface after the removal from the test furnace that were probably of a protective or passivation nature.