Anti-Galling Cold, Dry Forging of Pure Titanium by Plasma-Carburized AISI420J2 Dies

Tatsuhiko Aizawa,Tomomi Shiratori,Yohei Suzuki,Tomoaki Yoshino

doi:10.3390/app11020595

Tatsuhiko Aizawa, Tomomi Shiratori + Show 2 more

Open Access

https://doi.org/10.3390/app11020595

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Abstract

A bare AISI420J2 punch often suffers from severe adhesion of metallic titanium as well as titanium oxide debris particles in dry, cold forging of biomedical titanium alloys. This punch was plasma-carburized at 673 K for 14.4 ks to harden it up to 1200 HV on average and to achieve carbon supersaturation in the carburized layer. This plasma-carburized punch was employed in the cold, dry forging of a pure titanium wire into a flat plate while reducing the thickness by 70%. The contact interface width approached the forged workpiece width with increasing the reduction ratio. This smaller bulging deformation reveals that the workpiece is upset by homogeneous plastic flow with a lower friction coefficient. This low-friction and anti-galling forging process was sustained by an in situ solid lubrication mechanism. Unbound free carbon was isolated from the carbon-supersaturated AISI420J2 matrix and deposited as a thin tribofilm to protect the contact interface from mass transfer of metallic titanium.

Highlights

Pure titanium and titanium alloys have been highlighted as structural biomedical parts and tools because of their high specific strength and good biocompatibility [1]
The plasma-carburized AISI420J2 punch was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)–electron dispersive X-ray spectroscopy (EDX) to analyze the carbon-supersaturated iron–chromium matrix and its morphology
The cold, dry forging experiment was performed with the use of this punch to reduce thickness by 70%

Summary

Introduction

Pure titanium and titanium alloys have been highlighted as structural biomedical parts and tools because of their high specific strength and good biocompatibility [1]. The debris particles of TiO2 were prevented from depositing onto this coating surface This anti-galling process was sustained under in situ solid lubrication by the free carbon isolated from the carbon-supersaturated β-SiC coating surface and under the in situ formation of intermediate titanium oxide tribofilms on the contact interface. Owing to this galling-free mechanism, a pure titanium wire was forged under cold and dry conditions with a 70% reduction in thickness [5]. Simple shaping and upsetting can be put into practice in industries by using these β-SiC-coated

Results

Discussion

Conclusion