Relation between chemistry, solidification behaviour, microstructure and microporosity in nickel-base superalloys

Microporosity formation in nickel-base superalloys is studied experimentally and theoretically. A microporosity index, ΔP*, which depends on solidification parameters and alloy properties has been deduced. This index can be determined from parameters obtained by quantitative differential thermal analysis. The effect of mean alloying elements on the formation of microporosity is evaluated. Thus, aluminum, titanium and cobalt are found to increase and chromium to decrease microporosity. The effect of carbon depends on aluminum content and can be beneficial or detrimental.