Influence of target power and temperature on roughness and tribology of vanadium-carbon based coatings

Abstract

In the manufacturing of polyethylene terephthalate bottles, steel molds are used for the blowing process, these molds must have low roughness and friction coefficient as well as mirror-like aspect. This impacts final product features such as transparency and demolding. To achieve this, it is necessary to polish the mold cavities using abrasives such as diamond paste or alumina in suspension; however, no further protection against corrosion and wear can be achieved along its use. In this sense, physical vapor deposition coatings, such as balanced magnetron sputtering, are used to this aim giving average roughness values of 0.05 µm, along with superior corrosion and tribological behavior. Vanadium and Carbon coatings were deposited on American Iron and Steel Institute AISI 1045 steel, which is used in the manufacture of polyethylene terephthalate bottle molds, by means of sputtering technique with balanced magnetron. Deposition experiments were carried out in 8 samples during 30 minutes in an argon atmosphere using 2 to the 3-factorial design with different values of power applied to Vanadium and Carbon target and deposition temperatures. Tribological and roughness behavior was studied in order to evaluate the effect of power applied to target on those properties. In all samples low deposition temperature main effect leads to reduced roughness, in the same way, that low power applied to Vanadium target (40 Watts); however, that roughness is reached when the higher 50 Watts are applied on Carbon target. Similarly, lower coefficients of friction are associated with low roughness and therefore to abovementioned deposition conditions. There a clear effect of low power applied to Vanadium target and temperature to maintain reduced roughness and coefficient of friction which are optimal to coat polyethylene terephthalate bottle molds.