Ceramics international 21(1995)317-323 Performance of laminated ceramic Composite Cutting Tools Maurice F Amateau, Bruce Stutzman, Joseph C. Conway Joseph Halloran The Pennsylvania State University, P O. Box 30, State College, PA 16804, USA Greenleaf Corporation, Seagertown, PA 16433, USA ( Received 31 October 1994: accepted 1 December 1994) Abstract Laminated ceramic composite cutting tools have been developed which demonstrate improvements in strength, toughness, and thermal shock resistance compared to the conventional non-laminated ceramic composites. Silicon carbide whisker and titanium carbide particulate reinforced ceramic matrix composites have been designed as multilayer structures and fabricated into cutting tool inserts for evaluation in machining tests. Laminated ceramic composite designs exhibited significantly better wear resistances, as well as improved mechanical strength and toughness. Successful designs were achieved by minimizing residual core tensile stress and interlaminar stress while maximizing the compressive residual stress on the contact surfaces. These designs minimized flank wear and chipping 1 INTRODUCTION The main limitations of ceramics for cutting tools is their low tensile strength, fracture toughness, Cutting tool materials must have high hardness impact resistance and thermal shock resistance and stiffness to resist deformation under the high These property limitations make ceramic cutting cutting forces exerted in machining operations. tools prone to premature failure by chipping, crack They must also possess high wear resistance to ing or edge failure. Various methods may be maintain sharp cutting edges and permit high employed to increase the impact resistance and frac machining accuracy over extended periods of ture toughness of ceramics; however, whisker tough- time. Long cutting tool life also requires high ten- ening is particularly effective. 2 The low toughness sile and compressive strength, fatigue resistance, and the thermal shock resistance of monolithie high temperature strength, chemical inertness, ceramics can be significantly improved by the incor high fracture toughness, impact resistance and poration of discontinuous reinforcements such as high thermal shock resistance silicon carbide whiskers. Whiskers improve the Ceramics possess many, but not all, of the desir- toughness and strength of the ceramics through ablc propcrtics rcquircd for cutting tools and have crack bridging, whisker pullout, crack deflection, some of the characteristics necessary to counteract microcracking and transformation toughening he principal wear mechanisIms. The principal The toughness and strength can also b dvantages of ceramic cutting tools are hardness, improved through the use of thermoelastically stiffness, high temperature strength, and chemical tailored surface residual compressive stresses tability at elevated temperatures. Chemical stabil- Surface residual compressive stresses can be incor ity is particularly important in minimizing rake porated into ceramic laminates upon cooling by face crater wear. Minimizing reactive type wear introducing low coefficient of thermal expansion permits higher cutting speeds, which lowers cut- layers to the surface of the material. The residual ting forces thus minimizing work piece distortion surface compressive stresses resist surface tensile High temperature strength of ceramics also retains stresses typically generated through bending. The tool hardness and minimizes abrasive wear during compressive stresses can also serve to effectively extended cutting operations blunt or close cracks in the material. 5, Ceramics international Printed in Great Britain 0272-8842/95/$9.50 @1995 Elsevier Science Limited, England and Techna S r ICeramics International 21 (1995) 3 1 l-323 Performance of Laminated Ceramic Composite Cutting Tools Maurice F. Amateau,B Bruce Stutzman,B Joseph C. Conwaya & Joseph Halloran” ’ The Pennsylvania State University, P.O. Box 30, State College, PA 16804, USA b Greenleaf Corporation, Seagertown, PA 16433, USA (Received 31 October 1994; accepted 1 December 1994) Abstract Laminated ceramic composite cutting tools have been developed which demonstrate improvements in strength, toughness, and thermal shock resistance compared to the conventional non-laminated ceramic composites. Silicon carbide whisker and titanium carbide particulate reinforced ceramic matrix composites have been designed as multilayer structures and fabricated into cutting tool inserts for evaluation in machining tests. Laminated ceramic composite designs exhibited significantly better wear resistances, as well as improved mechanical strength and toughness. Successful designs were achieved by minimizing residual core tensile stress and interlaminar stress while maximizing the compressive residual stress on the contact surfaces. These designs minimized flank wear and chipping. 1 INTRODUCTION Cutting tool materials must have high hardness and stiffness to resist deformation under the high cutting forces exerted in machining operations. They must also possess high wear resistance to maintain sharp cutting edges and permit high machining accuracy over extended periods of time. Long cutting tool life also requires high ten￾sile and compressive strength, fatigue resistance, high temperature strength, chemical inertness, high fracture toughness, impact resistance and high thermal shock resistance. Ceramics possess many, but not all, of the desir￾able properties required for cutting tools and have some of the characteristics necessary to counteract the principal wear mechanisms. The principal advantages of ceramic cutting tools are hardness, stiffness, high temperature strength, and chemical stability at elevated temperatures. Chemical stabil￾ity is particularly important in minimizing rake face crater wear. Minimizing reactive type wear permits higher cutting speeds, which lowers cut￾ting forces, thus minimizing work piece distortion. High temperature strength of ceramics also retains tool hardness and minimizes abrasive wear during extended cutting operations. The main limitations of ceramics for cutting tools is their low tensile strength, fracture toughness, impact resistance and thermal shock resistance. These property limitations make ceramic cutting tools prone to premature failure by chipping, crack￾ing or edge failure. Various methods may be employed to increase the impact resistance and frac￾ture toughness of ceramics; however, whisker tough￾ening is particularly effective.‘,2 The low toughness and the thermal shock resistance of monolithic ceramics can be significantly improved by the incor￾poration of discontinuous reinforcements such as silicon carbide whiskers. Whiskers improve the toughness and strength of the ceramics through crack bridging,3 whisker pullout, crack deflection, microcracking and transformation toughening.4 The toughness and strength can also be improved through the use of thermoelastically tailored surface residual compressive stresses. Surface residual compressive stresses can be incor￾porated into ceramic laminates upon cooling by introducing low coefficient of thermal expansion layers to the surface of the material. The residual surface compressive stresses resist surface tensile stresses typically generated through bending. The compressive stresses can also serve to effectively blunt or close cracks in the material.5,6 317 Ceramics International Printed in Great Britain 0272-8842/95/$9.50 01995 Elsevier Science Limited, England and Techna S.r.1