Chemical vapor deposition and analysis of thermally insulating ZrO sub(2) layers on injection molds

High quality injection molding requires a precise control of cooling rates. Thermal barrier coating (TBC) of zirconia with a thickness of 20-40 mu m on polished stainless steel molds could provide the necessary insulating effect. This paper presents results of zirconia deposition on stainless steel substrates using chemical vapor deposition (CVD) aiming to provide the process parameters for the deposition of uniform zirconia films with such a thickness. The deposition was performed with zirconium (IV) acetylacetonate (Zr(C sub(5)H sub(7)O sub(2 )) sub(4)) as precursor and synthetic air as co-reactant, which allows deposition at temperatures below 600 degree C. The experiments were carried out in a hot-wall reactor at pressures between 7.5 mbar and 500 mbar and in a temperature range from 450 degree C to 600 degree C. Important growth parameters were characterized and growth rates between 1 and 2.5 mu m/h were achieved. Thick and well adhering zirconia layers of 38 mu m could be produced on steel within 40 h. The transient heat transfer rate upon contact with a hot surface was also evaluated experimentally with the thickest coatings. These exhibit a good TBC performance. ([copy 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)