Cooling rate and carbon content effect on the fraction of secondary phases precipitate in as-cast microstructure of ASTM F75 alloy

Microstructural evolution during isothermal aging and strain-induced transformation followed by isothermal aging in Co-Cr-Mo-C alloy: A comparative study

“…dendritic carbides enriched in chromium, as shown by X-ray line scan in Fig. 2, and expected to be M 23 C 6 [11,14,15].…”

“…The solution treatment at 1230 • C for 3 h contributed to complete elimination of primary grain boundary coarse carbides and coring which are responsible for brittleness [11,[14][15][16]. Implementing solution treatment caused to finer and uniform distribution of primary carbides (M 23 C 6 ) in the cobalt-rich matrix, as can be seen in Fig.…”

“…4 and 5, it seems that at early stages of aging, the area fraction of lamellar phases increases with aging time up to 16 h and then decreases drastically. Ramiırez-Vidaurri et al [15] have shown that this lamellar component corresponds to a eutectoid constituent that in an alloy with C content of 0.26 wt.% precipitates below 989 • C, when cooling rate is below 35 • C/min. In this work, owing to higher cooling rate (water quenching from solution temperature), no formation of lamellar component was observed after quenching, as can be seen in Fig.…”

“…Average grain size of 112.91 ± 58.98 m was obtained after solution treatment. In fact, normal grain growth due to annealing temperature causes various grain sizes depending on the heat treatments [11,14,15].…”

“…All in all, the total transformation of fcc (metastable) → hcp phase during isothermal aging, strongly depends on temperature, time and chemical composition of Co-Cr-Mo-C alloy [6,7,15,18]. As can be seen in Figs.…”