Coated cemented carbide tool life extension accompanied by comb cracks: The milling case of 316L stainless steel

• Published in: Wear 2019-01, Vol.418-419, p.133-139
• Main Authors: Zhang, Li, Zhong, Zhi-qiang, Qiu, Lian-chang, Shi, Hai-dong, Layyous, Albir, Liu, Shao-ping
• Format: Article
• Language: English
• Subjects: Abrasion; Abrasives; Aluminum oxide; Austenitic stainless steels; Carbide tools; Cemented carbides; Chipping; Coatings; Comb crack; Crack propagation; Cracks; Deformation mechanisms; Face milling; Failure mechanisms; Fatigue cracks; Fatigue failure; Life extension; Milling tool design; Nano-multilayered AlTiN based coating; Plastic deformation; Self-adaptive ability to plastic deformation; Stainless steel; Stress dissipation ability; Substrates; Tool life; Tool life extension; Widening
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2018.11.019

Two typical commercial coatings were deposited on a cemented carbide substrate, including CVD multilayered TiN/MT-TiC0.7N0.3/TiCNO/α-Al2O3 (cm-Al2O3 based) and PVD nano-multilayered Al0.55Ti0.45N/TiN (pn-AlTiN based). Performance and mechanisms for tool failure and tool life extension were investigated for the face milling of 316L stainless steel under a tough milling condition. The results show that the pn-AlTiN based coating exhibits a strong ability against delamination, abrasion wear and comb crack widening. As a result, its tool life is 2.1 times as long as the one with the cm-Al2O3 based coating. Edge chipping resulted from comb crack evolution is still the dominated fatigue failure mechanism for both the coatings. Internal formation of longitudinal submicron to nano-scaled cracks, accompanied by clear lattice fringes with a coherent relation between AlTiN and TiN was observed in a FIB-cut specimen with a size of 6.5 × 6.5 µm with a transmission electron microscope. For the pn-AlTiN based coating, the strong ability against comb crack widening stems from its strong self-adaptive ability to plastic deformation through the internal formation of submicron to nano-scaled cracks and the associated strong stress dissipation ability. A design concept for improving the milling tool life is discussed. •Tough milling parameters were chosen to stimulate two coatings’ natural response.•Strong stress dissipation ability is identified for nano-multilayered (pn) AlTiN/TiN.•Strong self-adaptive ability to plastic deformation is identified for pn-AlTiN/TiN.•Life extension mechanism accompanied by comb cracks is revealed for pn-AlTiN/TiN.•Design concept for improving milling tool life is discussed.