An Atomic Redistribution Study of the 440°C Ageing Kinetics in Maraging-300 Steel

Abstract

Mӧssbauer spectroscopy, X-ray diffraction and hardness measurements were used to investigate the atomic redistribution and phase transformation of solution-treated and 440°C aged Maraging-300 steel specimens. The ageing temperature that resulted in the best mechanical properties in this steel was 480ºC. At 440ºC, the formation of the precipitates that assure excellent mechanical properties of the maraging steel (Ni 3 Ti, Fe 2 Mo) was not expected. The results indicated that Mo and Ti redistribution was severe during the first hour of ageing. The mobility of the Ni atoms probably occurred during all stages of the ageing process, and the Co atoms remained close to Fe atomic sites. An irregular behaviour of the formation of paramagnetic phases containing iron was observed, and some evidence of the formation of these phases without Fe will be discussed. The formation of metastable phases was suggested and the possibility of austenite reversion was not discarded at this ageing temperature.

Hardening Effects of In-Situ Aging for a Laser Welded Maraging Steel

“…Maraging alloys belong to the Ultra-High Mechanical Strength Steels (UHSS) as could attain tensile strengths up to 3.4 GPa depending on composition and the thermomechanical treatments (Rohrbach and Schmidt, 1993). Different from ordinary UHSS, Maraging steel martensite is ductile and the maximum strength is obtained by aging (Silva et al, 2019). The phase transformations for produce the steel ingots are the origin of the name MARtensite and AGING.…”

“…Even with solid state processes failed to prevent softening of the joint because annealing produces fully martensite in cooling (Kellogg, 2012). Silva et al (2019) heat treated a class 300 Maraging steel from 1 to 100 h at 440C obtaining hardness ranging from 300 HV to 620 HV. These authors recorded the Moessbauer spectra for each aging time and noted that a high mobility of Mo and Ti atoms for times under 3 h.…”

Performance of Maraging Steel Sleeves Produced by SLM with Subsequent Age Hardening

“…Mössbauer spectrometry, as a very common technique in the case of various kinds of steels [ 20 , 29 , 30 , 31 , 32 ], has been utilized in order to determine iron-bearing phases. Transmission Mössbauer spectra (TMS) collected at room temperature are presented in Figure 15 a,b for the initial powder and 3D printed sleeve, respectively.…”

“…The spectra were fitted with a set of 5 Voigt-like sextets. G01-G04 components were utilized in order to describe the smeared sub spectrum very characteristic for martensite in maraging steel [29,30].…”

“…Table 4. Contributions and hyperfine parameters of fitted Mössbauer spectra components for initial powder sample and the sleeve (the recognition of martensite-like and austenite-like components according to [29][30][31][32][33][34][35] The mean values <B hf > differs very slightly (32.41 T − 32.24 T = 0.17 T) i.e., about 0.5%. Such small difference is a strong proof that the local atomic ordering is very similar in both samples despite significant difference in morphology and metallographic microstructure.…”