The influence of magnesium on carbide characteristics and creep behavior of the Mar-M247 superalloy

Effect of minor alloying additions on the solidification of single-crystal Ni-base superalloys

“…Nitrogen, whose content can be high in revert, has been reported to increase microporosity [7,8] during solidification of Ni-base superalloys. Studies have also shown boron to be effective at reducing carbide size, improving mechanical properties and retarding grain boundary cracking in polycrystalline Ni-base alloy [9][10][11][12]. In the case of single crystals, the addition of carbon and boron has proven beneficial in reducing solidification defects, improving the tolerance for minor solidification defects and improving mechanical properties [6,[14][15][16].…”

The effects of Mg microaddition on the mechanical behavior and fracture mechanism of MAR-M247 superalloy at elevated temperatures

“…[28][29][30][31][32] It is also proposed that carbide refinement may be associated with a decrease in carbide/matrix interfacial energy or the inhibition of coarse carbide growth. [33][34][35][36] However, little work has been reported on introducing Mg as a microalloying element in cast superalloys, which are generally poor in ductility and toughness at room and elevated temperatures. This property is essential both from the viewpoint of manufacturing concerns and service requirements where the rupture ductility is of importance.…”

The Role of Magnesium in Superalloys—A Review

“…Bor et al [22][23][24] observed that in MAR-M247 nickel based alloy, 0.008% Mg increased the number of MC on grain boundary, which significantly decreased creep rupture life and elongation of the alloy. effect of Mg on impact toughness was reported which is shown in Figure 5, which is possibly due to the decrease in interdendritic Laves eutectic ( Figure 6) and the refinement of interdendritic segregation of Nb and Ti, which allowed shorter homogenization cycle.…”

“…However, the properties were still better than the alloy containing negligible amount of Mg (0.0001% Mg). Bor et al [22][23][24] extensively worked on the effect of Mg on creep characteristics, fracture mechanism and carbide characteristics of MAR-M247, a Ni-base superalloy under 1255K/200 MPa and 1033K/724 MPa conditions. They observed that under the former testing condition 0.005% Mg refined and spheroidized MC carbide at GB, which enhanced the creep properties, whereas 0.008% Mg addition increased the number of MC at GB, which significantly decreased rupture life and elongation.…”

“…Mg formed an enriched layer of Mg surrounding the carbide and might influence the transport of carbon and carbide forming elements. This resulted in an isotropic growth of carbides during solidification and eventually led to the refinement and spheroidization of MC carbides both at the grain boundary and within the grain interior [4,[22][23][24]. The spheroidization resulted from Mg addition improves the stress distribution state at grain boundary thus decreases the possibility of wedge crack at the grain boundary [17].…”