Original Date: 03/08/1999
Revision Date: 01/18/2007
Best Practice : Thermolastically Tailored Cutting Tools
Cutting tools must have high hardness and stiffness to resist deformation under the high cutting forces exerted in machining operations. These tools must also be high-wear resistant to maintain sharp cutting edges and permit high machining accuracy over extended periods of time. The Applied Research Laboratory at the Pennsylvania State University (ARL Penn State) has developed laminated ceramic composite cutting tools, which demonstrate improvements in strength, toughness, and thermal shock resistance compared to conventional, non-laminated ceramic composites.
Using SiC whisker and TiC particulate reinforced ceramic matrix composites, the ARL Penn State designed multilayer structures and fabricated cutting tool inserts for evaluation in machining tests. The composites were fabricated using either AlO or SiN as the matrix, with TiC particulate, TiN particulate, or SiC whisker reinforcements. The laboratory modified the classical plate laminate theory to thermolastically tailor the laminate design and optimize residual stress, toughness, and tribological performance.
The ARL Penn State’s designs are considered hybrid composites by conventional laminate terminology since they use multiple compositions within a single laminate. Some of these designs used pure alumina surface layers to provide chemically inert material on the rake face, while others used TiC and SiC reinforcement alumina on this surface. The ARL Penn State chose laminate designs to avoid large tensile stresses within the lamina, and large differences in stresses between lamina to minimize delamination.
The laminated ceramic composite designs exhibit significantly better wear resistances as well as improved mechanical strength and toughness. The ARL Penn State achieved successful designs by minimizing residual core tensile and interlaminar stresses, while maximizing the compressive residual stress on the contact surfaces. These designs also minimized flank wear and chipping.
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