Low adhesion effect of TaO functional composite coating on the titanium cutting performance of coated cemented carbide insert

Highlights: • Life of tool with TaO coating is increased more than triple TiAlTaN single coating. • Tool life of commercial coating is improved 267% after adding TaO coating. • Friction coefficient is decreased to 0.82 with increasing TaO thickness to 150 nm. • TaO coating reduces adhesive wear of coated tools during machining titanium. Adhesive wear is one of the major reasons for short tool life during machining titanium alloys. This study presents a new kind of low adhesive wear TaO functional coating prepared by magnetron sputtering. The composite coating is composed by two layers of a solid solution TiAlTaN in bottom and a TaO (Ta₂O₅ or TaO_x) on top. Tool life of the TiAlTaN/TaO coatings is increased more than triple the TiAlTaN single coating by titanium cutting experiments. Cutting performance of commercial TiAlN-based coated tool is increased 267% after coating the TaO on the surface. Friction and wear between the coatings and Ti6Al4V counterpart have been conducted. The results show that both the friction coefficient of the coatings (from 1.05 to 0.82) and surface roughness (from 12.2 ± 0.6 to 7.1 ± 0.1 nm) are decreased by increasing TaO thickness from 0 to 150 nm. The adhesive bonds between coating and titanium also reduce with increasing the TaO thickness. This leads to the significantly reduction of the adhesion at the cutting tool tip after coated the TaO coating. This is because that the titanium is not easy to bind with the TaO coating by the calculated positive interaction energy between the Ta₂O₅ surface and pure Ti.