Oxidation and property evolution of AISI T5 steel under varying heat treatments

Abstract

This study evaluates the effect of heat treatment on the mechanical, tribological, and oxidation behavior of AISI T5 steel. The chemical composition was first characterized using spectroscopy and SEM. A two-year oxidation test conducted in humid and relatively dry atmospheres showed strong environmental sensitivity: in humid air, the oxidation rate reached 11.27×10-2 P/P0 per month with a sharp increase after 25 days, whereas in dry air it remained below1.35×10-2 P/P0 per month, following a linear and nearly flat trend indicative of a protective oxide scale. Heat treatment significantly increased hardness from 34.15 ± 0.59 HRC (untreated) to 62.70 ± 0.66 and 60.80 ± 0.48 HRC for water and oil quenched steels, respectively. Impact strength decreased accordingly, with oil quenching offering the best hardness-toughness balance (60.8 HRC, 2.08 Kcv). Instrumented indentation confirmed substantial surface strengthening, with HIT rising to 17.39 ± 0.29 uced by 81.3% (Q. Water) and 62.5% (Q. Oil), with faster run-in in the water-quenched condition. XRD revealed tempered martensite with Fe3W3C/Cr7C3 (Q. Water) and Co3W3C (Q. Oil), consistent with thermal conditions. This study provides new experimental data on the effects of 15-minute austenitization followed by oil or water quenching on the properties of AISI T5 steel, highlighting its potential for process optimization.