Although the ferritic stainless steel 410D (S41003) has a relatively simple chemical composition, with only 0.015% carbon by weight, previous studies indicate that this alloy can be fully or partially hardened by heat treatment. Therefore, the present work aims to analyze the effect of different heat treatment conditions on the microstructure and hardening of the material. As a methodology, two heat treatment conditions were performed. In the first condition, the samples were heated to 1000 ℃, varying the austenitizing time at 5 min, 30 min, 60 min, 120 min, and 240 min and then quenched in water. For the second condition, the samples underwent an intercritical annealing at 800 ℃ for 1 h and were cooled in the furnace. Afterwards, the samples were heated to 1000 ℃, varying the austenitizing time at 5 min, 30 min, 60 min, 120 min, and 240 min and quenched in water. The microstructural analysis indicated that the as-received material has a polygonal ferritic structure with Cr23C6 carbide precipitation, and the annealing treatment generated the precipitation of more chromium carbides. After the quenching treatment, the qualitative analysis corroborated previous studies indicating an increase in lath martensite due to the increase in grain size. The hardening results indicate that the alloy can be hardened by quenching, but when the material undergoes a prior intercritical annealing process, the hardness increases. Moreover, the longer the samples are held at the austenitizing temperature, the lower the post-quenching hardness, a phenomenon associated with the increase in austenitic grain size.
