The role of boron on a conventional nickel-based superalloy

Stress rupture tests of M951 superalloy containing various boron concentrations are performed at 1100 °C/40 MPa. The results show that boron in the range of 0.003–0.024% is beneficial to the rupture life. Further increase of boron contents leads to the drop of rupture life. The tensile tests at 1000 °C indicate that, despite the increase of tensile elongation, the tensile strength at 1000 °C is depressed by the boron doping. These effects of boron are explained in a terms of an easy grain boundary transfer between adjacent grains. Thus, large dislocation pileups in the vicinity of grain boundary are less likely. Thereby, the propensity for intergranular crack nucleation should be reduced. Besides, a way to estimate the volume of boride is proposed.