Microstructural characterization of the ferrous alloy ¹⁸Ni class 300 after heat treatments

Full text: Maraging steels are Ni-Fe alloys that possess strength levels reaching 2400 MPa with excellent ductility and toughness properties. Thus, this material can be used in many aerospace applications and nuclear industries [1-3].This work presents the microstructural characterization results for the maraging steel ferrous alloy 18 Ni class 300 after solution and aging heat treatments. The ferrous alloy 18 Ni class 300 was solution treated at 910°C for 1 hour then cooled to room temperature in air and aged at 510°C for 6 hours. The characterization of the maraging steel microstructure and composition were carried out through the following tests: optical emission spectroscopy (OES), Energy Dispersive Spectroscopy (EDS/SEM), X-ray Diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The composition of the maraging steel determined by OEM and EDS was within the standards for this steel. The X-ray diffraction results showed that the structure was mainly martensitic due to the presence of the main peaks (110), (200) and (200) which confirm this microstructure. Through the optical microscopy and electron microscopy, it was possible to examine the ferrous alloy 18 Ni class 300 grain structure; the ASTM grain size determined by the intercept method was 8 after the solution treatment and 9 after aging. References [1] ASM Metals Handbook. Heat-treating. ASM International. ASM Handbook Committee. 1991 Volume 4. [2] Adriano et al. High temperature creep resistance and effects on the austenite reversion and precipitation of 18 Ni (300) maraging steel. Materials Characterization. 2015. [3] Sha, Wei; Guo Zhanli. Modelling of microstructure, properties and applications. Woodshead Publishing. 2009. (author)