164
M. V. Mehta et al.
Nickel–chromium–molybdenum alloys with high Ni, very low Fe, and W and
approximately less than 15% Mo solidify with single austenite and devoid of interdendritic topological-closed-packed (TCP) phases. With increasing molybdenum
addition along with the presence of iron and tungsten, inter-dendritic topologicalclosed-packed (TCP) phases are developed during solidification [8, 25].
The Mo segregation behavior has a strong impact on the microstructural development, as increase in the nominal content of Mo resulted in a simultaneous increase
in the amount of eutectic constituents γ/σ and γ/ρ [23].
Solidification behavior of higher Mo, Fe, and W contains Hastelloy C-22 and
Hastelloy C-276 compared to Hastelloy C-4 studied by Cieslak et al. Nominal
composition of Hastelloy C-22 alloy is Ni—21Cr—13Mo—3Fe—2 W alloy [26],
and Hastelloy C-276 nominal composition is Ni—16Cr—16Mo—5Fe—4 W [27].
When the research was carried out by Cieslak et al. [4], multi-component liquidus
projections were not present, and microstructural development was judged with the
help of nickel–chromium–molybdenum isothermal projections [8].
Cieslak et al. [4] proposed equations of 1, 2 and 3, For the behavior study of the
minor elements such as W and Fe
Moeq = wt%Mo + wt%W
(1)
Nieq = wt%Ni + wt%Fe +
wt%Xi
(2)
Creq = wt%Cr
(3)
where
Xi = sum of minor elements.
Perricone et al. proposed new solidification sequence with multi-component
liquidus projections involving main five (nickel, chromium, molybdenum, iron,
and tungsten) elemental constitute for hastelloy C-22 and hastelloy C-276 using
of conjoining solidification-path calculations [28].
The above-given transformation sequences presented in Tables 5 and 6 are varied
Table 5 Alloy C-4, C-276, C-22 transformation sequence [4]
Transformation sequence
Alloy
L → L + γ → L + γ + TiC→ γ + TiC
Hastelloy C-4
L → L + γ → L + γ + ρ→ γ + ρ→ γ + ρ + μ
Hastelloy C-276
L → L + γ → L + γ + σ→ γ + σ→ γ + σ + ρ→ γ + σ + ρ + μ
Hastelloy C-22
Table 6 Alloy C-276, C-22 transformation sequence [28]
Transformation sequence
Alloy
L → L + γ → L + γ + ρ→ γ + ρ
Hastelloy C-276
L → L + γ → L + γ + ρ→ L + γ + ρ→ L + γ + σ + ρ→ γ + ρ + σ
Hastelloy C-22
M. V. Mehta et al.
Nickel–chromium–molybdenum alloys with high Ni, very low Fe, and W and
approximately less than 15% Mo solidify with single austenite and devoid of interdendritic topological-closed-packed (TCP) phases. With increasing molybdenum
addition along with the presence of iron and tungsten, inter-dendritic topologicalclosed-packed (TCP) phases are developed during solidification [8, 25].
The Mo segregation behavior has a strong impact on the microstructural development, as increase in the nominal content of Mo resulted in a simultaneous increase
in the amount of eutectic constituents γ/σ and γ/ρ [23].
Solidification behavior of higher Mo, Fe, and W contains Hastelloy C-22 and
Hastelloy C-276 compared to Hastelloy C-4 studied by Cieslak et al. Nominal
composition of Hastelloy C-22 alloy is Ni—21Cr—13Mo—3Fe—2 W alloy [26],
and Hastelloy C-276 nominal composition is Ni—16Cr—16Mo—5Fe—4 W [27].
When the research was carried out by Cieslak et al. [4], multi-component liquidus
projections were not present, and microstructural development was judged with the
help of nickel–chromium–molybdenum isothermal projections [8].
Cieslak et al. [4] proposed equations of 1, 2 and 3, For the behavior study of the
minor elements such as W and Fe
Moeq = wt%Mo + wt%W
(1)
Nieq = wt%Ni + wt%Fe +
wt%Xi
(2)
Creq = wt%Cr
(3)
where
Xi = sum of minor elements.
Perricone et al. proposed new solidification sequence with multi-component
liquidus projections involving main five (nickel, chromium, molybdenum, iron,
and tungsten) elemental constitute for hastelloy C-22 and hastelloy C-276 using
of conjoining solidification-path calculations [28].
The above-given transformation sequences presented in Tables 5 and 6 are varied
Table 5 Alloy C-4, C-276, C-22 transformation sequence [4]
Transformation sequence
Alloy
L → L + γ → L + γ + TiC→ γ + TiC
Hastelloy C-4
L → L + γ → L + γ + ρ→ γ + ρ→ γ + ρ + μ
Hastelloy C-276
L → L + γ → L + γ + σ→ γ + σ→ γ + σ + ρ→ γ + σ + ρ + μ
Hastelloy C-22
Table 6 Alloy C-276, C-22 transformation sequence [28]
Transformation sequence
Alloy
L → L + γ → L + γ + ρ→ γ + ρ
Hastelloy C-276
L → L + γ → L + γ + ρ→ L + γ + ρ→ L + γ + σ + ρ→ γ + ρ + σ
Hastelloy C-22