Microstructural Evolution in Laser Deposited Nickel-Titanium-Carbon in Situ Metal-Matrix Composites (Preprint)

摘要

Laser deposition of a mixture of elemental nickel, titanium, and carbon (graphite) powders with varying compositions, via the laser engineered net shaping (LENS) process, has resulted in novel in situ metal-matrix composites. The microstructure in these in situ composites can be substantially tailored depending on the ratio of graphitic carbon to titanium added. A lower C/Ti ratio results in a harder composite consisting of primary titanium carbide precipitates within a eutectic matrix consisting of nickel and titanium carbide while a higher C/Ti ratio results in a softer composite consisting of primary graphitic carbon bundles within the same type of eutectic matrix. These composites have been characterized in detail using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy mapping), and, transmission electron microscopy.