High wear performance of the dual-layer graded composite diamond coated cutting tools

• Wear resistance of the diamond coated tools with various architectures was studied.
• High speed machining tests were conducted on the Alm–30%SiCp composite material.
• Graded composite diamond coating has enhanced the uncoated tool life by 18.5 times.
• Interfacial adhesion integrity of the coating is the vital contributing factor.

In the present experimental study, wear performance of the diamond coated cutting tools with various coating architectures was studied by turning Alm–30%SiCp metal matrix composite material. Chemical vapor deposited (CVD) diamond can be classified into nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) that are known for their distinct characteristics. Diamond coatings with three different coating architectures were deposited for the machining study; (i) mono-layer MCD coating (MCD/WC–Co), (ii) dual-layer composite diamond coating (NCD/MCD/WC–Co) and (iii) dual-layer graded composite diamond coating (NCD/transition-layer/MCD/WC–Co). Wear performance of the diamond coated (3 architectures), uncoated and commercial TiN coated tools was evaluated and compared by conducting high speed machining tests. Superior wear performance of the diamond coated tools was clearly evident from the tool wear measurements. The poor tool life (t < 1 min) of the uncoated and TiN coated tools was attributed to the abrasive action of the hard SiC reinforcement particles. Dual-layer graded composite diamond coated (t = 14.7 min) and mono-layer MCD coated (t = 13.5 min) tools showed superior machining performance in comparison to that of the dual-layer composite diamond coated tool (t = 9.8 min). Dual-layer graded composite diamond coatings deposited with the concept of transition-layer are the prospective tool coatings for high performance machining applications due to their top-layer nanocrystallinity and enhanced interfacial integrity.

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