Chemical Vapor Deposition of Polycrystalline Al₂O₃

Abstract

Polycrystalline A1,OJ was chemically vapor-deposited onto sintered AL03 substrates by reaction of AlCl, with (1) HzO, (2) C02:Hz, and (3) 0, at 1000" and 1500°C and 0.5 and 5.0 torr. Although the thermodynamics of all these reactions predict the formation of solid A1,0, the deposition rate of the first reaction was considerably greater than that of the second. The third reaction was so slow that no measurable deposit was formed in 6 h at 1500°C. Formation of dense deposits of 0r-A1,0~ was favored by increasing temperature and decreasing pressure. Microstructural examination of the dense deposits showed long columnar grains, the largest of which extended through the deposit from the substrate to the surface.

Chemically Vapour Deposited Alumina Coatings on High Speed Steel Cutting Tools

“…0.06 atm. This tendency to form more friable deposits of AI 2 0 3 at high total pressures has also been observed by Park et al [42,44] and Wong and Robinson [46] in their work on the CVD of AI 2 0 3 coatings on TiN coated cemented carbide and sintered alumina substrates respectively. Park et al [42] observed Al 2 0 3 powder on the surface of AIP3 coatings deposited at a deposition temperature of 1125°C and a total pressure of 400 torr (0.53 atm), the other depositions conditions employed being as previously specified in Section 2.3, whereas Park et al [44] observed AI 2 0 3 powder on the surface of the AI 2 0 3 coatings deposited at total pressures of 200 and 400 torr (0.26 and 0.53 atm, respectively) with the other depositions conditions as quoted earlier in Section 2.3.…”

“…A number of workers have investigated the effect of deposition temperature on AI,03 coatings chemically vapour deposited on various substrates, paying particular attention to its effect on nucleation [29,32,41], deposition rate [31,36,37,42,43] surface morphology [24,27,43,44,48], preferred orientation [43] and crystal structure [38,[45][46][47].…”

“…Investigations have been carried out into the effect of total pressure on the nucleation [29], deposition rate [27,31,36,37,42], surface morphology [27,42,44,46] and preferred orientation [44] of Al 2 0 3 coatings chemically vapour deposited on various substrates.…”

“…The AICI, evaporation unit and associated pipework, the latter heated to -200°C [16,27,46] to maintain the AICI, in gaseous form.…”

The protective properties of thin alumina films deposited by metal organic chemical vapour deposition against high-temperature corrosion of stainless steels

“…In the first process AICI 3 and water or CO2-H2 are used to form A12 03 at 1000-1200 °C and at a pressure of 0.5-5 Torr [5,6]. The second process has been described by Aboaf [7].…”