Galling-Free Dry Near-Net Forging of Titanium Using Massively Carbon-Supersaturated Tool Steel Dies

Area of Science:

• Materials Science
• Tribology
• Manufacturing Engineering

Background:

• Titanium forging typically requires lubricants to prevent galling and wear.
• Existing tool steels are prone to adhesion and wear when forging titanium, especially under dry conditions.
• Developing advanced die materials is crucial for efficient and sustainable titanium processing.

Purpose of the Study:

• To develop and evaluate Massively Carbon-Supersaturated (MCSed) tool steel dies for dry forging of titanium.
• To investigate the galling-free forging behavior and lubrication mechanisms of MCSed dies.
• To assess the impact of MCSed dies on product quality and die performance in titanium forging.

Main Methods:

• Plasma-immersion carburizing process applied to SKD11 and ACD56 tool steels at 673 K for 14.4 ks to achieve massive carbon supersaturation.
• Upset forging tests of pure titanium bars using MCSed SKD11 dies to evaluate friction and galling.
• Microstructure analysis of die contact surfaces to identify lubricating tribofilm formation.
• Eyeglass frame forging using MCSed ACD56 dies to assess surface quality and performance.

Main Results:

• MCSed SKD11 dies demonstrated extremely low friction (μ = 0.05) and minimal bulging during titanium upsetting.
• An in situ formed free-carbon film was identified as a tribofilm, effectively reducing friction and adhesive wear.
• MCSed ACD56 dies significantly improved surface quality of forged eyeglass frames, reducing average roughness from 4.12 μm to 0.99 μm.
• A 30% reduction in applied load was observed with MCSed ACD56 dies, indicating improved forging efficiency.

Conclusions:

• MCSed tool steel dies provide an effective solution for galling-free titanium forging under dry conditions.
• The in situ generated free-carbon tribofilm is key to the superior lubrication and wear resistance of MCSed dies.
• This technology enhances forged product quality and prolongs die life, offering significant advantages for titanium manufacturing.