Tribological assessment of the SiO2 coating deposited by sol-gel process toward cutting tool coating.

Abstract

A more economic and thinner coating than the commercial ones was developed to improve the tribological behavior of highspeed steel (HSS) tools. This work focuses on performance of the SiO2 coating was compared to uncoated HSS pins as well as coated ones (titanium nitride (TiN)) deposited by physical vapor deposition (PVD). The pin-on-disk test was carried out under a constant normal load of 10 N by applying sliding speeds of 40, 55, and 70 m·min−1. The lowest values of the friction coefcient (µ) and the specifc wear coefcient (k) were found for the coated pins. SiO2 coating presented performance equivalent to the commercial TiN coating for the sliding speeds of 40 and mainly 55 m·min−1, revealing a mild abrasive wear mechanism with the ferritic spheroidal graphite iron (SGI) interface surface. Thus, the sol-gel coating suggests being a promising protection for cutting tools submitted to abrasive wear when machining SGI workpiece at cutting speeds 3 times higher than those used with uncoated HSS tools, e.g., in drilling and tapping processes. Hereupon, SiO2 is capable of substituting TiN coating for cutting speeds up to 55 m·min−1 with advantage of being an easier deposition process applied to any geometry without needing of high temperatures.