Investigation on the Modification Methods to Ceramic Cutting Tools

Abstract

There are too many methods to enhance the performance of ceramic cutting tools. All the methods can be sorted into two types: inner modification and surface modification. One of the main method to the inner modification of ceramic cutting tools is dispersion strengthening. Usually, in order to enhance the performance of ceramic cutting tools, some dispersed phases of TiN, TiC or TiCN, Al2O3, and/or ZrO2, and so on, and/or some whiskers, or fibers were added into the ceramic matrixes. And the new types of cutting tools, which possessed much more excellent performance than the original ones, were called composite ceramic cutting tools. For the composite Si3N4-based ceramic, Al2O3-based ceramic, and TiCN-based cermet, the cutting efficiency could be enhanced to 3~10 times, compared with cemented carbide tools. And they can be used for rough and finish machining of various cast iron workpieces and hardened steels, respectively, including milling and planning. Ion implantation is a surface modification for ceramic cutting tools. With certain doses of metals, for example, titanium, zirconium and chromium, and so on, implanted into the ceramics, the hardness, Young’s modulus, fractural toughness, and bending strength, etc., can be enhanced. For Al2O3 and Si3N4 ceramics, the hardness, Young’s modulus, and bending strength increased with a maximum factor of 50%, and the flank wear decreased with a factor of 2~12, compared with the unimplanted ceramic cutting tools. However, the main shortcoming of ion implantation to modify ceramics is the thickness of modified layers. They are, usually, too thin for cutting tools. The so-called PHEDP, pulsed high energy density plasma, is another surface modification method for ceramic cutting tools proposed recently. With such method, much thicker coatings of TiN, TiCN and (Ti,Al)N, etc, were deposited onto Si3N4 and WC ceramic cutting tools.The main merits involved in high hardness and Young’s modulus of the coatings, low residual stresses, and good adhesive strength between the coatings and substrates. And the flank wear of the as-depositedtools decreased with a factor of 5~10.