Effect of 316L Stainless Steel Fabrication on Oxidation Resistance, Surface Morphology, and Hot Tensile Behavior

Abstract

Samples based on 316L stainless steel were prepared by conventional manufacturing process (CM) and laser powder bed fusion (L-PBF). Surface morphology changes under air oxidation in the temperature range 600-900 °C were carried out. Tensile tests were carried out in the temperature range of 700-900 °C for strain rates between 0.001 and 0.1 s−1. The materials showed good oxidation resistance up to 700 °C. The CM and L-PBF material had a high mass gain instability and similar microstructures developed under high temperatures were found in both alloys. Increased temperature increases Cr concertation in the L-PBF material up to 40 at.% at 800 °C and a rich Fe based oxide is formed at 900 °C. Slightly thicker oxide scales were formed in the CM than in the L-PBF material.The hot tensile tests reveal that a fast work hardening occurs for all hot tensile tested samples up to a strain of approximately 0.025. Low temperatures and high strain rates within the investigated range promote a second work hardening regime, while a plateau in the flow stress is observed at high temperatures and low strain rates. The highest yield stress and peak stress values are reached at 700 °C. The yield stress is nearly independent of the strain rate at 700 °C. It decreases with a decrease in strain rate for 800 and 900 °C, and it decreases with an increase in temperature. The elongation till fracture varies from 10 to 22%, and it is strongly influenced by defects inherent of the L-PBF process.