Chemical and structural characterisation of nickel based superalloys doped with minor and trace elements

A study was carried out to assess the effect on mechanical and structural properties of a nickel based superalloy (CM247LC) upon addition of excess quantities of silicon, manganese, iron and tin added it at various concentrations and also to see the maximum extent to which they can be tolerated. Chemical and structural characterisation were carried out by using glow discharge quadrupole mass spectrometry (GD-QMS), scanning electron microscopy (SEM) and electron probe micro analysis (EPMA) techniques. Recovery of the elements Si, Mn, Fe, and Sn was found to be 7, 40, 55, and 15%, respectively. Variations of the concentrations of these elements from top to bottom of the cast were also studied. The transverse and longitudinal microstructures of nominal and doped alloys were investigated. The mechanical properties such as tensile, stress rupture strengths, ductility, and rupture life were tested at aero-engine operating conditions. The effects of the dopants on the microstructure as well as on the mechanical properties of the alloy are summarised.