This study experimentally investigated the effect of surface textures on the tribological mechanism of nitrided titanium alloy (Ti–6Al–4V). The titanium alloy samples were nitrided at various temperatures ranging from 750 to 950 °C for 10 h in a plasma nitriding furnace. Then, surface textures were fabricated on the polished titanium alloy and plasma nitrided samples by laser process system. The surface roughness, microhardness, and constitution of samples treated by single nitriding and samples treated by composite technology were characterized. The tribological properties of the samples were investigated on a CSM ball-on-disc tribometer. The results show that plasma nitriding effectively enhances the wear resistance of the substrate. The wear rate decreases first and then increases with the increase of nitriding temperature, and the wear rate reaches the minimum at 900 °C. However, the increase in roughness caused by nitriding treatment leads to an increase in the friction coefficient. It is found that surface textures can obviously reduce the friction coefficient of the nitrided titanium alloy. In addition, it can also reduce the wear rate of titanium alloys after nitriding at 900 and 950 °C. It can be concluded that the nitriding and surface texturing combined treatment can obviously reduce the friction coefficient and wear rate at the nitriding temperatures of 900 and 950 °C. This is attributed to the combined effect of high hardness of nitride layers and the function of micro-trap for wear debris of surface textures.

Based on comparisons of two all-polymer solar cells based on PTzBI:N2200 and PNDN-T:N2200 blends, factors limiting the device characteristics are investigated.

Diamond-like carbon (DLC) coatings containing 0.7%, 5.8%, and 23.3% Ti were deposited via pulsed cathodic arc deposition and magnetron sputtering on AISI 316L stainless steel substrates. The varied Ti content was controlled by setting Ti target current at 3, 5, and 7A. The composition, microstructure, mechanical, and tribological properties of Ti-doped DLC (Ti-DLC) coatings were investigated using X-ray photoelectron spectroscopy, Raman spectroscopy, nanoindentation, and ball-on-disc tribometer. The results show that TiC formed when Ti content in the coating was higher than 5.8 at% and the I_D/I_G ratios increased gradually with the increasing Ti content. Ti-DLC with 0.7 at% Ti had the highest H/E and H³/E² ratios and exhibited optimal tribological properties under lubrication, especially when zinc dialkyldithio-phosphate (ZDDP) was contained in the oil. Furthermore, ZDDP tribofilms played an important role in wear reduction by protecting the rubbing surfaces against the adhesion and suppressing the tribo-induced graphitization of DLC coatings.

It has been proved that surface nanocrstallization pretreatment is beneficial to plasma nitriding of steel by enhancing nitrogen diffusion, while the tribological properties of the nitrided nanostructured steel under boundary lubrication are not clear. In this work, AISI 316 L stainless steel with and without ultrasonic cold forging technology (UCFT) pretreatment was plasma nitrided at 500 °C for 4 h. The effects of UCFT pretreatment on the microstructure and properties of the nitrided layer and the tribochemical interactions between the nitrided layer and friction modifier molybdenum dithiocarbamate (MoDTC) and antiwear additive zinc dialkyldithio-phosphate (ZDDP) were investigated using SRV tribometer, scanning electron microscopy (SEM), vickers hardness tester, optical microscope, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Surface analyses confirm the formation of a 20 μm thick nitrided layer on the UCFT-pretreated sample and it had higher hardness than that on the unpretreated sample. Furthermore, the nitrided UCFT-pretreated sample presented better synergetic effect with MoDTC and ZDDP on tribological behaviors than the nitrided unpretreated sample. This is attributed to the higher contents of Mo, S, Zn, P, and MoS2/MoO3 ratio in the tribofilms on the nitrided UCFT-pretreated sample.