MICROESTRUTURA E DUREZA DO AÇO S41003 QUANDO SUBMETIDO A DIFERENTES TRATAMENTOS TÉRMICOS

Abstract

. Stainless steel is known for its resistance to corrosion and oxidation at high temperatures. However, common ferritic stainless steels generally have low hardness and theoretically are not hardenable by heat treatment. Although ferritic stainless steel 4100D (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 with 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 carried out, in the first condition the samples were heated to 1000 ℃, varying the austenitization time in 5 min, 30 min, 60 min, 120 min and 240 min, then quenched in water. For the second condition, the samples underwent an intercritical annealing at 800 ℃ for 1 h and cooled in the oven, then the samples were heated to 1000 ℃, varying the austenitization time in 5 min, 30 min, 60 min, 120 min and 240 min and quenched in water. The microstructural analysis indicated that the material, in its delivery state, has a polygonal ferritic structure with precipitation of Cr 23 C 6 type carbides, and the intercritical annealing treatment led to an increase in the precipitation of chromium carbide. After the quenching treatment, the qualitative analysis corroborated with previous studies that indicate an increase in the martensite volume rate, due to the dissolution of the chromium carbide and the increase in the grain size. The hardening results indicate that the alloy can be hardened by quenching in water when heated to a high temperature, in addition, the previously annealed material has a higher hardness when quenched. However, with increasing austenitization time, there was a decrease in hardness, associated with an increase in austenitic grain size.