Microstructure and Corrosion Behavior of AISI 316 Steel Layers Deposited on AISI 347 Steel Substrate by Laser Metal Deposition

Abstract

The aim of this work was to evaluate the porosity, microstructure, hardness, and electrochemical behavior of AISI 316 steel layers deposited on an AISI 347 steel substrate using the LMD process. Depositions of two, four, and six layers with a 0.5 mm height for each layer were performed at a speed of 375 mm/min, a power of 250 W, a focal distance of 5 mm, and without overlapping laser tracks. The results showed epitaxial growth of the deposited layers in relation to the substrate and a predominantly austenitic microstructure with ferrite as the substrate. The deposited layers presented a dendritic microstructure with a mean porosity of 4.5%. The porosity decreased as the number of deposited layers increased, affecting the pitting corrosion resistance. The sample with six deposited layers showed greater pitting corrosion resistance, whereas the corrosion current speeds were similar for the studied samples. Vickers hardness tests showed that the hardness decreased as the distance from the substrate increased, and the hardness decreased close to the remelted regions.

Keywords

• laser metal deposition
• additive manufacturing
• stainless steels
• microstructure
• pitting corrosion