Corrosion Resistance of Additive Manufactured 17-4PH DMLS Steel After Heat Treatment and Shot Peening Process

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Abstract
Additively manufactured steel is not free of drawbacks and defects. Such disadvantages include high roughness and lower hardness compared to conventional steel. The 17-4PH steel is a grade designed for precipitation hardening. The application of 17-4PH steel ranges from turbine blades, pumps, valves, and propellers for aerospace, maritime, nuclear power plants, and medical instruments. This grade of steel is often applied where high mechanical performance and good corrosion resistance are required. Considering these factors, it was decided to use a heat treatment designed for conventional steel of this steel grade, that is, a precipitation hardening process followed by shot peening. The use of a constant supersaturation temperature of 1040°C and aging at 450°C made it possible to evaluate the mechanical properties depending only on the type of treatment used. Different peening media were also used to determine the effect of the medium on the properties of the surface layer after the peening process. To determine the surface characteristics, tests were carried out using optical profilometry, above that, hardness was tested, and corrosion resistance was examined using potentiodynamic polarization tests in a 3.5% NaCl environment. The aim of this study is to evaluate the effect of precipitation hardening combined with SP on the corrosion resistance of 17-4PH steel. Results obtained for steel produced using DMLS technology were compared with conventionally fabricated 17-4PH steel. Heat treatment contributed to a greater increase in hardness for the DMLS made steel. The corrosion resistance turned out to be dependent mainly on the roughness that increased after the Shot Peening process. The main purpose of the study was to evaluate the effects of precipitation hardening combined with shot peening on the corrosion resistance of 17-4PH steel. Results obtained for steel produced using DMLS technology were compared with conventionally produced 17-4PH steel.

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