SOLUTION AND PRECIPITATION OF CHROMIUM CARBIDE DURINGTHE FABRICATED PROCESS OF Cr₇C₃ / Ni₃Al COMPOSITE

A Cr₃C₂-Ni₂Al welding wire was produced by pressureless sintering process in vacuum. When thewelding wires were welded on the surface of carbon steel , carbide particles reinforced Ni₃Al base composite wasformed due to the physical heat of arc and Ni-Al exothermic reaction. XRD shows that Ni react s with Al to formNi₃Al and Cr₃C₂ is dissolved during welding. Most of Cr and C react to form Cr₇C₃ phase except that a few dissolve into Ni₃Al mat rix. The size of Cr₇C₃ particles mainly depends on the cooling rate of different welding regions.In addition , as the solid solubility of Cr in Ni₃Al is much larger than that of C and Cr₃C₂ changes to Cr₇C₃ duringwelding , some graphites are formed in welding layers. The graphites mainly segregate on welding outer layers dueto it s low density and high melting point . The room and high temperature hardness of Cr₇C₃ / Ni₃Al composite ismuch higher than that of stellite alloys. It is predicted that Cr₇C₃ / Ni₃Al composite may become an att ractive potential candidate for high2temperature surface wear-resistant material.