Performance of DLC-Coated Micro-Tools in Micro-Milling of Titanium-Based Biomedical Alloys

ASLANTAŞ K., DİKİCİ B., ÖZKAYA E.

INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING, 2026 (SCI-Expanded, Scopus)

Özet

This study investigates the micro-milling behaviour of three biomedical titanium grades, commercially pure titanium (CpTi), Ti6Al7Nb, and Ti6Al4V, using Diamond-Like Carbon (DLC) coated micro end mills under identical cutting conditions. The novelty of this work lies in the direct and mechanism-oriented comparison of these clinically relevant titanium materials under fixed tool geometry, DLC coating, and cutting parameters. This approach isolates the effect of alloy type and relates the observed machinability response to alloy-dependent microstructural, thermal, and adhesion-related characteristics. Machining performance was evaluated as a function of cutting length by analyzing cutting-force evolution, areal surface roughness (Sa and Sz), 3D surface topography, burr formation under up- and down-milling conditions, and progressive tool wear. Changes in tool diameter and flank wear were measured using calibrated USB-microscope images. The final measurements were verified by SEM, which was also used to characterize the resulting wear morphology. The results show a clear alloy-dependent response. Ti6Al4V exhibits the earliest and most pronounced degradation in surface integrity and burr formation, accompanied by strong adhesion/BUE-related instabilities and accelerated tool deterioration. Commercially pure titanium (CpTi) produces comparatively stable roughness trends but shows increased burr development at longer cutting lengths due to ductility-driven plastic flow and material transfer. Ti6Al7Nb provides the most stable overall behaviour, maintaining more uniform surfaces and a comparatively controlled burr response with less severe adhesion features. Across all alloys, burr width increases with cutting length and is generally higher in down-milling than in up-milling, consistent with minimum chip thickness and ploughing effects in the exit region. SEM-based chip analysis further corroborates these differences through distinct flow and segmentation characteristics. The findings contribute to the research by clarifying alloy-specific wear and burr-generation mechanisms in DLC-assisted titanium micro-milling and provide practical guidance for industrial process planning where edge integrity and surface quality are critical, such as precision biomedical component manufacturing.