Effects of Phosphorus Addition on Creep Properties of Wrought γ′ Strengthened Ni-Based Superalloy

Influence of Phosphorus Addition on the Stress Rupture Properties of Direct Aged IN706 Superalloy

“…It was determined that P in the as-solutioned state is beneficial for the stress rupture properties by comparing the data obtained under the standard and nonstandard heat treatment schemes. It was previously suggested that the main mechanism of the beneficial effect of P addition is that moderate amounts of P in the as-solutioned state segregated to the grain boundaries, which increased grain boundary cohesion; reduced grain boundary free energy and diffusivity, which also served to prevent intergranular oxidation; and controlled the precipitation of the grain boundary phase [1][2][3][4][5][6][7][8][9]11]. However, P in the as-solutioned state was not always beneficial when the alloy was subjected to direct aging heat treatment, as shown in Figure 5.…”

“…Due to the increasing requirements on materials' thermal capabilities and on fuel efficiency, high temperature materials research has become more critical. Previous research has demonstrated that a minor addition of phosphorus (P) markedly improved the mechanical properties of some wrought Ni-Fe-based superalloys [1][2][3][4][5][6][7][8][9][10]. For example, P could increase the time to rupture more than 3-fold, and reduce the steady state creep by more than one order of magnitude in alloys such as IN718 and GH761, without obvious influence on tensile properties and grain size [1,2,11].…”

“…There have been several studies on the mechanisms behind the beneficial effects of minor P addition. These suggested that P tended to strongly segregate to grain boundaries, which enhances grain boundary strength [1,4,8,13], controls grain boundary precipitation [2][3][4][5][6][7]14,15], and inhibits intergranular oxidation [3].…”

Effects of boron addition on the microstructure and creep properties of a Ni-Fe-based superalloy weld metal alloy

“…For instance, small precipitates such as M 23 C 6 carbides dispersed on grain boundaries are generally considered to be beneficial to the grain boundary properties. It has been accepted that discretely distributed M 23 C 6 carbides along the grain boundaries are beneficial to creep as they restrain grain boundary crack propagation and grain boundary sliding [38]. Moreover, Guo et al proposed that chain M 23 C 6 carbides could hinder grain deformation and reduce the steady-state creep rate, improving the creep resistance of materials [39].…”

“…In the boron-bearing weld metal, the higher density of discrete M 23 C 6 carbide particles could strengthen the grain boundaries and inhibit the propagation of grain boundary cracks [38]. However, in the boron-free weld metal, the precipitation of M 23 C 6 at the grain boundaries was rare, and the M 23 C 6 spacing was large, which resulted in insufficient grain boundary strengthening.…”