17-4PH is a precipitation hardening stainless steel widely used as an engineering structural material in different industrial sectors, such as aerospace, chemical and biomedical fields due to its ease of fabrication, high strength and elevated corrosion resistance. The peculiar properties of this steel are promoted by both the reinforcement induced by the precipitation of submicron-sized secondary phases occurring during the ageing treatment and its low carbon content. Nowadays, additive manufacturing has gained much attention and, among others, the Direct Energy Deposition technology (DED) is a promising process. The DED technique consists of the deposition of laser melted powders and it is increasingly used to manufacture or repair complex mechanical parts. In the present investigation 17-4 PH powders were used as a feedstock to perform single-track depositions over an AISI 316L plate employing different process parameters such as laser power, scanning speed and powder feed rate. Some geometrical features of the tracks were preliminary studied. Microstructural investigations were carried by means of optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) to deeply investigate the metallurgical characteristics of the joints. Different dilutions were measured according to the process parameters, finding that these conditions affect not only the porosity content but also the evolution of phases along the cross section of the track. Besides that, it was observed an effect of a precipitation hardening treatment performed for a 17-4PH material, from which different hardness and microstructure were detected before and after the heat treatment.

17-4 PH SS single tracks DED depositions over AISI316L: macro and microstructural investigations

Cindy Morales Bazaldua;Mattia Merlin;Annalisa Fortini;Gian Luca Garagnani;
2022

Abstract

17-4PH is a precipitation hardening stainless steel widely used as an engineering structural material in different industrial sectors, such as aerospace, chemical and biomedical fields due to its ease of fabrication, high strength and elevated corrosion resistance. The peculiar properties of this steel are promoted by both the reinforcement induced by the precipitation of submicron-sized secondary phases occurring during the ageing treatment and its low carbon content. Nowadays, additive manufacturing has gained much attention and, among others, the Direct Energy Deposition technology (DED) is a promising process. The DED technique consists of the deposition of laser melted powders and it is increasingly used to manufacture or repair complex mechanical parts. In the present investigation 17-4 PH powders were used as a feedstock to perform single-track depositions over an AISI 316L plate employing different process parameters such as laser power, scanning speed and powder feed rate. Some geometrical features of the tracks were preliminary studied. Microstructural investigations were carried by means of optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) to deeply investigate the metallurgical characteristics of the joints. Different dilutions were measured according to the process parameters, finding that these conditions affect not only the porosity content but also the evolution of phases along the cross section of the track. Besides that, it was observed an effect of a precipitation hardening treatment performed for a 17-4PH material, from which different hardness and microstructure were detected before and after the heat treatment.
2022
17-4PH, DED, microstructure, porosity, geometrical analysis
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2504588
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