Tribocorrosion performance of Nitrogen-doped diamond like carbon coating by high power impulse magnetron sputtering technique

Abstract

Nitrogen-doped diamond like carbon film is promising in biological applications, studying the synergistic tribocorrosion performance is indispensable. In this paper, Nitrogen-doped diamond like carbon films were deposited on AISI 304L austenitic stainless steels and Si substrate by using the high power impulse magnetron sputtering technique using Ar and N<sub>2</sub> as precursors at room temperature. The effect of target pulse duration on the structure, mechanical properties, corrosion resistance and tribocorrosion properties in Hank's equilibrium salt solution and the corresponding mechanism were studied. The results of scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and nano-hardness test showed that the nitrogen-doped diamond like carbon coatings prepared at a target pulse duration of 60 μs showed the sp<sup>3</sup> bonding content of 33.9% with the hardness of 12.4 GPaand the root mean square roughness of 0.63 nm. With the increase in pulse duration to 90 μs, the sp<sup>2</sup> bonding increased, meanwhile the surface roughness increased. The results of potentiodynamic polarization indicated that the Nitrogen-doped diamond like carbon coating prepared at 60μs had best corrosion resistance with the corrosion current density of 7.65 × 10<sup>–8</sup> A·cm<sup>–2</sup>. The effect of the target pulse duration on tribocorrosionbehaviour of the Nitrogen-doped diamond like carboncoating was investigated in Hank’s solution by a reciprocating tribometer equipped with a three-electrode electrochemical cell.The coatings at 60 μs exhibited excellent tribocorrosion properties with high open circuit potential of 39 mV, low COF of 0.05 without pitting corrosion due to high corrosionresistance, low contact angel and dense microstructure.The results indicated that corrosion can be accelerated by friction, but it also affect the mechanical properties of the Nitrogen-doped diamond like carbon coatings. The increase in pulse duration to 90 μs, leading to the reduction of sp<sup>3</sup> bonds which can form a cross-linking structure. The degraded cross-linking structure decreased the corrosion resistance of the coating via the increased porosity in the coating, which weakened the interfacial strength of the coating, and ultimately led to failure of the coatingunder the action of wear.