Structure and Properties of the Tool Ceramics with Hard Wear Resistant Coatings

This work presents studies of the structure and functional properties of coatings deposited onto indexable inserts made of nitride and sialon tool ceramics with the required properties, i.e. high adhesion, microhardness, high resistance to abrasive and diffusion wear in working conditions of high-performance cuttings tools. In the present paper the results of the investigations of the structure, texture, mechanical and functional properties of the Ti(C,N), (Ti,Al)N, Ti(C,N)+(Ti,Al)N coatings were presented. The 80% increase in the hardness of the coatings in comparison to the substrate material was reported. Test coatings are characterized by good adhesion to the substrate. The maximum Lc load of (Ti,Al)N coat applied to the substrate from the nitride ceramics is equal to 42 N. In the studied coatings compressive stresses were found. The results of mechanical properties investigations, especially tribological ones correlate with the results of exploitation tests carried out during the cutting test.

The Effect of PVD and CVD Coating Structures on the Durability of Sintered Cutting Edges

In the work it was demonstrated that the exploitative stability of edges from tool ceramics and sintered carbides coated with gradient and multilayer PVD and CVD coatings depends mainly on the adherence of the coatings to the substrate, while the change of coating microhardness from 2300 to 3500 HV0.05, the size of grains and their thickness affect the durability of the edges to a lesser extent. It was found that some coatings showed a fine-grained structure. The coatings which contained the AlN phase with hexagonal lattice showed a considerably higher adhesion to the substrate from sialon ceramics rather than the coatings containing the TiN phase. Better adherence of the coatings containing the AlN phase with hexagonal lattice is connected with the same kind of interatomic bonds (covalent) in material of both coating and ceramic substrate. In the paper the exploitative properties of the investigated coatings in the technological cutting trials were also determined. The models of artificial neural network, which demonstrate a relationships between the edge stability and coating properties such as: critical load, microhardness, thickness and size of grains were worked out.

Titanium Carbide Reinforced Composite Tool Ceramics Based on Alumina

The present study reports some preliminary results obtained by reinforcing Al2O3-10 wt% ZrO2 (partially stabilized with Y2O3 -Y5 and monoclinic phase m-ZrO2) composite with TiC phase in amount of 5 wt %. Ceramic composites were prepared on the basis submicro and nano scale trade powders. Apparent density, porosity, Vicker’s hardness, Young’s modulus and fracture toughness (KIC) were determined. Wear resistance (Vn) very important property for tool ceramics was specified by the speed of mass lost. Scanning electron microscopy (SEM) to observation of the fracture surface microstructure was used. The titanium carbide reinforced composite tool ceramics based on alumina exhibit high hardness, fracture toughness (critical stress intensity factor KIC increase up to 5,2 MPa m1/2), high elastic moduli and higher wear resistance in related to pure alumina. Cutting tests confirm the high performance of these ceramic composites.

Crack Profile under Vickers Indents

The present work is focused on complex evaluation of crack profiles, created around Vickers indents in two types of cutting tool ceramics, namely in the Al2O3 + ZrO2 ceramics and -Si3N4. The geometry of Vickers indents is investigated using two different evaluation methods. The first one is based on the application of serial sectioning from the indented specimen surface. The second method consists in the layer removing from plane perpendicular to the indented surface. These evaluation methods are convenient for determine the shape of created cracks and profiles of deformed area developed around the investigated indents. The mentioned methods contribute to the understanding of physical engineering principles resulting from the radial/median and lateral crack formation as the important characteristics influencing the reliable technical application of investigated ceramic materials.

Cutting Properties of PVD and CVD Coated A2lO 3 + TiC Tool Ceramic

The paper presents investigation results of tribological and cutting properties of the coatings deposited with the PVD and CVD techniques on cutting inserts made from the Al2O3 + TiC tool ceramics. Tests were carried out on the inserts made from ceramics, uncoated and PVD or CVD-coated with gradient, mono-, multilayer and multicomponent hard wear resistant coatings composed of TiN, TiCN, TiAlN, TiAlSiN and Al2O3 layers. Substrate hardness tests and micro hardness tests of the deposited coatings were made on the ultra-micro-hardness tester. It was demonstrated, basing on the technological cutting tests of grey cast iron (260 HB), that putting down onto the tool ceramics the thin anti-wear PVD and CVD coatings increases their abrasion wear resistance, which has a direct effect on extending tool life of the cutting edge.