Technical Note: Hardness, Corrosion Behavior, and Microstructural Characteristics of a Selective Laser Melted 17-4 PH Steel

Abstract

In this work, we report the hardness and corrosion behavior of a selective laser melted 17-4 PH steel. Microstructure analysis using a scanning electron microscope (SEM) revealed a fine-grained material with a grain size of 1 μm. Phase analysis using SEM-EBSD (electron backscatter diffraction) revealed a ferritic-austenitic microstructure with 96% ferrite and 4% austenite. The material was also found to bear a combination of <001> and <111> fiber texture. The grain boundary character distribution revealed 68% low-angle grain boundaries, 10% CSL boundaries with predominantly Σ3 boundaries, and 21% high-angle grain boundaries. The Vickers hardness of this material was found to be quite high at 3.66±0.17 GPa which is probably due to the fine-grained structure of the material. Potentiodynamic polarization tests in 3.5 wt% NaCl solution yielded a corrosion current density, icorr of 1.4 × 10−6 A/cm2 and corrosion potential, Ecorr of −55 mVAg/AgCl electrode. Immersion tests in salt water for a period of 96 h showed hardly any pit formation although an AISI 304 stainless steel bearing grain size of 29 μm showed significant pit formation during the same time period.