Galling-Free Cold and Warm Forging of Titanium Wires to Flat Plates by SiC-Coated SiC dies

Abstract

Pure titanium and titanium alloys were difficult to be forged and press-forged because of their easiness in galling to die and punch surfaces during metal forming. β-SiC coated SiC dies were developed to perform a galling free cold forging of pure titanium wire up to the higher reduction of thickness than 50%. Since the thickness of this SiC coating was 4 mm, various cavities and micro-punches were formed into coating by micro-machining. The pure titanium and β-phase titanium alloy wires were employed as a work for cold and warm forging to investigate the effect of flow stress on the forging behavior up to the reduction of thickness by 70% under the controlled holding temperature. The contact interface of β-SiC coating to the work was precisely analyzed to describe the in situ solid lubricating process on the interface. The free carbon agglomerates isolated at the center of contact interface from the carbon supersaturated β-SiC coating, and, worked as a solid lubricant to prevent the β-SiC coating punch and die from galling during forging under high reduction of thickness.