Advances in processing of Ni3Al-based intermetallics and applications

The intermetallic-based alloys for structural applications have been an active field of research around the world for the last 20 years. Several major breakthroughs have occurred in this field during this time period. These breakthroughs include: (1) the dramatic effects of boron on ductility improvement for Ni3Al at ambient and high temperatures, (2) effect of chromium addition for intermediate temperature ductility improvement of Ni3Al, and (3) identification of an environmental effect from hydrogen generated by the reduction of moisture in air by aluminum in the aluminides. The knowledge of the compositional effects has led to the development of Ni3Al-based alloys, which allowed them to be taken from laboratory-size melts to commercial applications. This paper will describe the advances in melting practice, casting practices, solidification modeling as it applies to static and centrifugal castings and weld repairs, and welding of castings. This paper will also describe various applications of Ni3Al-based alloys and their current status of commercialization.