Abstract
Dense β-SiC coating with 3C-structure was utilized as a dry cold forging punch and core-die. Pure titanium T328H wires of industrial grade II were employed as a work material. No adhesion or galling of metallic titanium was detected on the contact interface between this β-SiC die and titanium work, even after this continuous forging process, up to a reduction in thickness by 70%. SEM (Scanning Electron Microscopy) and EDX (Electron Dispersive X-ray spectroscopy) were utilized to analyze this contact interface. A very thin titanium oxide layer was in situ formed in the radial direction from the center of the contact interface. Isolated carbon from β-SiC agglomerated and distributed in dots at the center of the initial contact interface. Raman spectroscopy was utilized, yielding the discovery that this carbon is unbound as a free carbon or not bound in SiC or TiC and that intermediate titanium oxides are formed with TiO2 as a tribofilm.
Highlights
Pure titanium has been utilized for metallic parts and tool components in various medical and biomedical applications due to its well-defined bio-compatibility [1]
Filmcontact formation on the contact interface and to investigate the role of free carbon agglomerates from the SiC coating on the solid lubrication under dry cold forging with a high reduction
Dry cold forging with a higher reduction in thickness than 50% is necessary for near-net shaping of titanium wires or bars for medical parts or tools
Summary
Pure titanium has been utilized for metallic parts and tool components in various medical and biomedical applications due to its well-defined bio-compatibility [1]. Its metal forming and forging often suffers from high friction and wear by its severe adhesion or galling [2]. Since heat is generated—even during cold forging—at the contact interface between die and work materials, this galling behavior is enhanced when the interface temperature exceeds the critical temperature [3]. The reduction in thickness in its forming and forging must be lowered as much as possible to be free from galling, when using the tool steel dies or tungsten carbide cobalt tools [4]. As pointed out in [5,6,7], this titanium galling process advances in two mechanisms. The fresh titanium surface adheres to the die surface by mass transfer so that the friction coefficient abruptly increases and results in seizure
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