Microwaves at 2.45 GHz have been used to ignite the Self propagating High temperature Synthesis (SHS) of Ni and Al powder mixtures to produce NiAl and a complex Ni-Al-Ti intermediate layer on titanium. The use of microwaves allows to selectively convey energy to the reacting powders, even during and after SHS, thus prolonging the existence of liquid phases and promoting the formation of a well adhered interface between titanium and the newly formed NiAl. The intermediate layer, belonging to the Ni-Al-Ti system, presents an interlocking microstructure, which provides increased mechanical properties with respect to the parent polycrystalline NiAl. Wear resistance of the complex Ni-Al-Ti layer was measured in dry-sliding against alumina using a ball-on-disk tribometer. Micro-hardness, elastic modulus, and scratch resistance (constant load, single- and multi-pass) were also measured, showing that the Ni-Al-Ti layer presents increased performances with respect to polycrystalline NiAl obtained by microwave assisted SHS.
Tough and wear resistant Ni-Al based thick intermetallic coatings on titanium Obtained by microwave assisted SHS / Veronesi, P.; Rosa, R.; Poli, G.; Casagrande, A.; Cammarota, G. P.. - 3:(2008), pp. 71-76. (Intervento presentato al convegno European International Powder Metallurgy Congress and Exhibition, Euro PM 2008 tenutosi a Mannheim, deu nel 2008).