Enhancing mechanical, wear and corrosion properties of wire arc additively manufactured 308LSi stainless steel structures through cold forging and annealing processes

Wire arc additively manufactured (WAAMed) parts often require some degree of post-processing operations to improve their quality and then enhance their lifetime performances in service conditions. In this work, wire arc additive manufacturing (WAAM) was used to fabricate AISI 308LSi wall structures, and then, post-processing treatments including annealing, cold forging, and a combination of cold forging and annealing were applied to enhance the quality of the fabricated walls. Thereafter, the microstructure, density, percentage porosity, hardness, tensile, wear, and corrosion properties of the walls (as-deposited and post-processed) were examined. The effects of the annealing, cold forging, and a combination of the cold forging and annealing processes on the quality of the WAAMed AISI 308LSi walls were determined and then compared. Highly dense walls were deposited via WAAM. The density increased to within 99.6% of the as-received AISI 308LSi, and the porosity was estimated to be < 0.5% after forging and a combination of forging and annealing post-processing. The hardness of the as-deposited wall (≈ 153 HV) was found to increase by 14.1% and 8.5% after the cold forging and a combination of cold forging and annealing, respectively. The post-annealing process resulted in the highest increase in ductility (≈ 31%), but the highest improvement in tensile strength (≈ 7.5%) was produced by the combination of the cold forging and annealing post-processing. Post-cold forging processing followed by a combination of cold forging and annealing processing yielded improvements in wear and corrosion resistances of the WAAMed AISI 308LSi wall structures. This work has established the suitable post-processing methods for enhancing the quality of WAAMed structures.