Performance improvement and friction reduction mechanism of Al2O3/Ti(C,N)/CaF2@Al2O3 self-lubricating ceramic tool for machining Cr15Ni60 alloy

Nickel-based alloys commonly used in spacecraft and wear-resistant coatings have excellent hardness and corrosion resistance. However, their high strength presents great machining challenges. Conventional metal cutting tools suffer severe friction and wear when machining these alloys, resulting in poor cutting performance. Ceramic tools feature high hardness, heat resistance, and excellent chemical stability. They also exhibit low metal affinity and little adhesion, making them widely used for machining difficult to cut materials. Using spark plasma sintering (SPS), Al 2 O 3 /Ti(C,N)/CaF 2 @Al 2 O 3 self-lubricating ceramic tools were produced and tested against commercial Al 2 O 3 /Ti(C,N) cutters for machining the Ni-based alloy Cr15Ni60. Compared with the commercial tools, self-lubricating inserts reduced axial, radial, circumferential and overall cutting forces by 17.0 %, 13.1 %, 9.7 % and 11.4 % on average, and lowered rake-face friction coefficient and cutting temperature by 4.1 % and 25.8 %. Analysis of the friction reduction mechanism in self-lubricating ceramic tools machining nickel-based alloys reveals under cutting forces and friction, solid lubricants continuously precipitate from the tool and uniformly distribute across tool-workpiece contact zone. This forms a dynamically balanced lubricating film that reduces friction between the tool, workpiece, and chips. Consequently, cutting forces, cutting temperatures, and coefficient of friction are lowered while machining performance is enhanced.