Mechanical, Macro- and Nano-Tribological Properties, and Corrosion Behavior of carbon-based Coatings Deposited by PVD and PACVD on AISI 420 Steel?

E. DALIBON; L. ESCALADA; K. BAKOGLIDIS; S. P. BRÜHL; S. N. SIMISON; L. HULTMAN; E. BROITMAN

Conferencia; ICMCTF'15 - International Conference on Metallurgical Coatings & Thin Films; 2015

Diamond-like carbon (DLC) and carbon-nitride (CNx) coatings deposited on steel machine components are ofindustrial interest for tribological applications due to potential reduction in friction, wear and corrosion. In thispaper we compare the mechanical, macro- and nano-tribological properties, and corrosion behavior of DLC filmsdeposited by PACVD and CNx films deposited by magnetron sputtering.The substrates were heat-treated AISI-420 SS-discs. DLC coatings were deposited by PACVD using acetyleneprecursor at TS=150ºC for 2h, obtaining films of ~2.5 μm-thick, with an adhesive a-Si interlayer. CNx films weredeposited using MF magnetron-sputtering in a mixture of Ar/N2 at TS=150 ºC and 100V bias for 6 h using anindustrial CemeCon CC800/9-ML system, resulting films of ~1 μm-thick, with an adhesive Cr interlayer.The coating microstructure and composition were analyzed by SEM, XPS and Raman. Adhesion was evaluatedby Rockwell-C indentations and Scratch Test. The macrotribological properties were evaluated by pin-on-disktests with alumina balls, while the nanomechanical and nanotribological properties were measured by aTriboindenter-TI950 with a conical diamond tip. Salt spray tests (ASTM-B117) and electrochemical experimentswere conducted in order to evaluate the corrosion behavior.CNx samples, containing 17 at% nitrogen, present a dense microstructure. The film hardness (H) and reducedelastic modulus (Er) are 21 GPa and 155 GPa, respectively, while the friction coefficient μ=0.065 and a wear rateof 5.1 x 10-6 mm3/Nm were measured at an initial Hertzian pressure of 8.5 GPa. DLC films containing 23%hydrogen with H=20 GPa and Er=250 GPa present 20% C-C sp3 and macro-μ=0.04. Both DLC and CNx filmshave the adhesion value HR=1. For coated samples, no sign of corrosion were observed after salt-spray tests, andpassive current densities remained very low, while the unprotected steel dissolved actively. The advantages ofeach film under different tribological and corrosion situations are highlighted.