Structural modifications of M35 steel submitted to thermal gradients in plasma reactor

Heat transfer between plasma and a solid material occurs mainly due to the radiation and collision of particles onto the material surface. In this process, the heat is transferred from the surface to interior of the material. In a solid material, depending on the particles collision rate and the thermal conductivity, there will be a thermal gradient along and across surface of the samples, caused by thermal peak, with consequent local microstructural modifications. In this work, quenched samples of AISI M35 steel (diameter: 9.5 mm and thickness: 3.0 mm) were tempered in plasma of H2, using hollow cathode configuration and work pressure of 4 mbar. Microstructural characterization of the samples was carried out by SEM and optical microscopy. Analyzing the microstructure and hardness (surface and profile), the thermal gradient in the samples was evaluated.