Ultrahigh-Temperature Nb-Silicide-Based Composites

Abstract

This article reviews the most recent progress in the development of Nb-silicide-based in situ composites for potential applications in turbine engines with service temperatures of up to 1350°C. These composites contain high-strength Nb silicides that are toughened by a ductile Nb solid solution. Preliminary composites were derived from binary Nb-Si alloys, while more recent systems are complex and are alloyed with Ti, Hf, W, B, Ge, Cr, and Al. Alloying schemes have been developed to achieve an excellent balance of room-temperature toughness, fatigue-crack-growth behavior, high-temperature creep performance, and oxidation resistance over a broad range of temperatures. Nb-silicide-based composites are described with emphasis on processing, microstructure, and performance. Nb silicide composites have been produced using a range of processing routes, including induction skull melting, investment casting, hot extrusion, and powder metallurgy methods. Nb silicide composite properties are also compared with those of Ni-based superalloys.

Solidification Process and Mechanical Behavior of the Nb/Nb₅Si₃ Two Phase Alloys in the Nb-Ti-Si System

“…2,28,29) The recent development in the Nb-silicide based composites is reviewed in the several papers. [33][34][35][36][37][38] Extensive studies have been made on the Nb-silicide based Fig. 1 The Nb-Si binary phase diagram.…”

Co‐Re‐based Alloys: A New Class of High Temperature Materials?

“…However, there is a limit and given the long term nature of material development, it is essential to search now for solutions beyond the temperature capability of Ni-based superalloys. For this reason, substantial international research is underway, focussing on ceramics, [1,2] intermetallic materials such as NiAl, [3,4] refractory metals such as Nb-based and Mo-based alloys, [5][6][7][8] as well as noble metals mimicking the c/c′-microstructure of superalloys. [9][10][11][12] The difficulty faced in all these new developments is that these materials have at least one pronounced weakness regarding the above mentioned key properties, and the challenge is to find acceptable solutions.…”

“…For example, much improved oxidation resistance has been reported for certain refractory alloys and significant patent activity is noticeable in this field. [5][6][7][8] Nevertheless, none of the evaluated material systems has come to the point were an acceptable property mix has been reached, allowing for demanding applications in the hot section of gas turbines. For this reason, it seems sensible to further search for alternative solutions, which have not been explored so far.…”

Microstructure Evolution and Mechanical Properties of a Directionally Solidified Nb-Ti-Si-Cr-Al-Hf-Dy Alloy

“…As one type of high-temperature intermetallic compound, niobium silicide possesses many superiorities, such as excellent high-temperature creep strength and high melting point (about 2793 K) [4,5]. Therefore, the niobium silicide has been thought as a potential material to apply in super high-temperature environment.…”