What other materials apart from conventional nickel and steel superalloys can be used as a first stage turbine blade material?
Turbine blades must withstand high tensile stresses at their blade roots and be resistant to cyclic stresses from fluctuating fluid dynamic loads- all of this at very high temperatures, and over great numbers of thermal cycles. This argues in favor of metallic blades and against ceramics in this application, because they perform better against fracture in tension and fatigue crack propagation.