Aging behaviour of cobalt free chromium containing maraging steels

Abstract

all at.-%), using hardness measurements, electron microscopy of replicas and thinfoils, atom probe field ion microscopy (APFIM), and thermochemical calculations. Two different families of inter metallic phases (Ti 6 Si 7 Ni16 G phase and 11 Ni3 Ti) have beenfound to contribute to age hardening. The composition and morphology of these precipitates were studied in deformed and undeformed alloys after aging at 420-570°C for various times. In addition, reverted austenite has beenfound in the aged structure. Results obtained using AP F I M are compared with equilibrium thermodynamic calculations and previous AP F I M studies of conventional Cr free low Al and Si maraging steels having higher Mo contents.MSTj1558

Comments onSmall-angle neutron scattering analysis of the precipitation behaviour in a maraging steelby Staron, Jamnig, Leitner, Ebner & Clemens (2003)

“…Their analyses of the experimental results led to the conclusion that the precipitates formed are solely the intermetallic G-phase, Ti 6 Si 7 Ni 16 , with none of the Ni 3 Ti type. This is in contradiction with what was reported by Gemperle and Sha et al (Gemperle et al, 1992;Sha et al, 1993c), who studied virtually the same alloy using atom-probe ®eld ion microscopy (APFIM) and observed the existence of both Ni 3 Ti and the Ti 6 Si 7 Ni 16 G-phase. Formation of reverted austenite was also observed when the alloy was over-aged.…”

Precipitate modification in PH13-8 Mo type maraging steel

“…Visual inspection might further indicate co-segregation of all elements, especially of Ti and Al. These elements are the most relevant ones for formation of the expected G-phase and g-phase precipitates, as observed in similar alloys [14,29]. To prove this the Ti and Al concentrations in each individual cluster shown in Fig.…”

“…A further type of precipitate phase, termed the G-phase, was found by Gemperle et al [29] in Ti-containing maraging steels alloyed with Si. The G-phase exhibits the chemical composition Ti 6 Si 7 Ni 16 and precipitates primarily on grain boundaries.…”

“…The G-phase exhibits the chemical composition Ti 6 Si 7 Ni 16 and precipitates primarily on grain boundaries. Depending on the chemical composition of the alloy, the G-phase (Ti 6 Si 7 Ni 16 ) and the g-phase (Ni 3 Ti) can precipitate either simultaneously or separately [29]. The shape of the g-phase is thought to be rod-like, while the G-phase shows a spherical morphology.…”

Microstructure and mechanical properties of a 2000 MPa grade co-free maraging steel

“…Gemperle et al reached a conclusion after investigation in a Fe-Ni-Cr-Si-Mo-Ti maraging steel system that the reverted austenite has a larger degree of influence on hardness and strength over the coarsening of precipitates. [36] With decreasing strength after hightemperature aging, the yield-to-tensile strength ratio also continues to decrease, i.e., there is a large strain-hardening rate. This confirms the effect of austenite on mechanical properties.…”