Effect of Heat Treatment Duration on Microstructure and Properties of 2205 Duplex Stainless Steel Fabricated by Laser-Directed Energy Deposition

In this work, the microstructural evolution and comprehensive performances (mechanical, wear, and corrosion resistance) of LDED-fabricated 2205 DSS subjected to heat treatment at 1000 °C for different holding durations (5 min, 10 min, 30 min, and 60 min) were systematically investigated. The results indicate that the austenite content gradually increases with the extension of heat treatment time, reaching a peak value of 51% at 30 min. Meanwhile, the austenite morphology transforms from dendritic grains to equiaxed grains, accompanied by the massive precipitation of intragranular austenite (IGA) and obvious elemental enrichment behavior. In terms of mechanical and functional performances, the microhardness decreases slightly with prolonged heat treatment, with a total reduction of only 7%. The elongation increases continuously, while the yield strength and tensile strength remain relatively stable. Additionally, the wear coefficient and wear rate present a trend of first decreasing and then increasing. The minimum wear rate of 48.32 × 10−6 mm3/(N·m) is obtained at the heat treatment duration of 30 min, which is 83.4% lower than that of the untreated sample. Moreover, the optimal corrosion resistance is achieved after 30 min of heat treatment, with the corrosion current density decreasing by 45.8% relative to the as-built specimen. These results demonstrate that heat treatment at 1000 °C for 30 min is an optimal processing parameter to significantly optimize the microstructure and comprehensive performances of LDED-2205 DSS.