In the present preliminary study, a martensitic stainless steel (AISI 420/X46Cr13/DIN1.4034) in annealed condition has been friction stir processed under different conditions: Dry and Wet Friction Stir Processing. Furthermore, in some tests a previous Laser Hardening was done in order to modify the surface of the martensitic stainless steel before being processed by friction stir. The optical examination of the processed zone showed a complex microstructure at the nugget and at HAZ and TMAZ zones, depending on the cooling rate and mechanical deformation degree during processing. All the processing conditions considered in this work allowed to obtain higher hardness values than those achieved using conventional Quench & Tempering treatments. On the other hand, a strong grain size reduction in the processed zone has been also observed. Correlation between microstructure - hardness - and processing parameters for the different processing conditions were established.
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