Tsutomu Ikeda

Phase formation and characterization of hard coatings in the TiAlN system prepared by the cathodic arc ion plating method

Abstract Hard Ti x N and (Ti 1− x Al x )N films were prepared using the cathodic arc ion plating method. When the ratio of the partial pressure of N 2 to the evaporation rate of titanium was reduced, the resulting phase in the TiN system changed from cubic TiN to tetragonal Ti 2 N, and then to h.c.p. α-Ti. When the AIN content in the TiNAlN solid solution was increased, the films, from TiN up to (Ti 0.3 Al 0.7 )N, exhibited a cubic structure. As the AlN content increased, the lattice parameter monotonically decreased from 4.26 A for TiN, to 4.16 A for (Ti 0.3 Al 0.7 )N. With a further increase in AlN content, (Ti 0.15 Al 0.85 )N films were found to have a wurtzite structure. It was concluded that the crystal structure of the ternary TiAlN system along with the wide-ranging solubility of AlN in TiN is typical for the isostructural group of cubic titanium-based nitrides. The (Ti,Al)N coatings were stable in air at a temperature of 800°C, whereas the TiN films began to oxidize at a temperature of 550°C. It was found that protective layers of amorphous aluminum oxides formed on top of the (Ti,Al)N films during elevated temperature oxidation tests which protected the film from further oxidation. The crystallized TiO 2 that was formed on the TiN film did not give the same protection. The nicrohardness and wear resistance of the (Ti,Al)N films were also investigated.

Formation of cubic boron nitride films by arc‐like plasma‐enhanced ion plating method

Thin cubic boron nitride (cBN) films were synthesized at 350 °C on various substrates such as silicon, stainless steel, TiN‐coated WC–Co and WC–Co by means of an arc‐like plasma‐enhanced ion plating process. In this process, polycrystalline cBN films were obtained at deposition rates of 0.004 to 0.03 μm/min. The infrared spectra showed strong absorption at 1050 cm−1, indicating cubic structure of the deposited film. The electron diffraction patterns also showed the cubic structure, with a lattice parameter of 3.63 A. It is inferred that ion bombardment during film growth plays a important role in the formation of cBN films. The cBN films deposited in this process had a high compressive stress of 4×1010dyn/cm2, which is significantly greater than the value of hard amorphous boron nitride (iBN) films, 1.6×1010dyn/cm2. The internal stress of cBN films was greatly reduced if iBN was used as a buffer layer between cBN and substrate.

Properties of (Ti1−xAlx)N coatings for cutting tools prepared by the cathodic arc ion plating method

(Ti,Al)N coatings with several Ti/Al ratios were deposited on Si and WC–Co substrates by the cathodic arc ion plating method. The crystal structure was found to be cubic B1 type, which is isostructural with the titanium‐based nitrides. Morphology of the (Ti0.4Al0.6)N and TiN films was investigated, using transmission and scanning electron microscopy. The films seemed to have a less columnar structure than expected. The (Ti,Al)N films containing less than 75 mol % AlN had higher hardness than for the pure TiN films. Similarly, (Ti,Al)N coatings displayed superior oxidation resistance at elevated temperatures. Overall, (Ti,Al)N coated cutting tools offer significantly better performance characteristics compared to the tools with TiN coatings.

Structure and properties of (Ti1−xAlx)N films prepared by reactive sputtering

(Ti1−xAlx)N films with several different Ti-to-Al ratios were deposited on silicon substrates by reactive cosputtering from Ti and Al targets in an ArN2 discharge. The crystal structure of the films was found to be cubic B1 type up to 50 mol.% A1N content. With further increase in the A1 content, the films of (Ti0.31Al0.69)N and (Ti0.29Al0.71)N were found to have mixed phases of hexagonal and cubic structures. The (Ti1−xAlx)N films had a well-developed cubic columnar structure with open voids which rendered lower hardness values than for stoichiometric single-crystal TiN.

Cubic boron nitride films synthesized by low‐energy ion‐beam‐enhanced vapor deposition

Single phase‐cubic boron nitride (cBN) films have been synthesized by means of the low‐energy ion‐beam‐enhanced vapor deposition method. Cubic BN films were deposited at 4 nm min−1 by electron‐beam evaporation of boron with N2+Ar ion beam bombardment under the energy range of 500–600 eV, at ion beam current density around 0.4 mA cm−2, and also, could be obtained in both cases with external rf or dc substrate biasing. The infrared spectra showed strong absorption at 1090 cm−1, which was shifted significantly towards a higher wave number due to the residual internal stress in the cBN films. High‐resolution transmission electron microscopy of cBN films deposited showed that the microstructure consists of polycrystalline particles with a size of 10 nm.

Effect of hydrostatic pressure on the phase transition of ferroelectric PbTiO3

Abstract The effect of hydrostatic pressure on the dielectric constant of the Nb-doped lead titanate ceramics was measured up to 60 kbar at room temperature. From the previously observed pressure dependence of lattice parameters and the present results, it is concluded that the tetragonality decreases linearly with a slope of −7.6×10 −4 /kbar and that the pressure dependence of the tetragonal-cubic transition temperature is −8.4K/kbar.

Pressure induced phases of the BaTixMn1−xO3 system

The phase relation of the perovskite-like structures in the system BaTixMn1−xO3(x=0–1) has been studied at high pressure. The quenched high pressure phases are found to have in order of 2H, 9R, 4H, 6H, and the cubic perovskite structure with increasing pressure. Furthermore, it is proposed that the perovskite-like structures can be represented in terms of the stacking sequence of six compound layers.