Ultrasonic cavitation erosion of gas nitrided Ti-6Al-4V alloys.
Ultrasonic cavitation erosion experiments were performed on Ti-6Al-4V alloys samples in annealed, nitrided and nitrided and subsequently heat treated state. The protective oxide layer formed as a result of annealing and heat treatment after nitriding is eliminated after less than 30 min cavitation time, while the nitride layer lasts up to 90 min cavitation time. Once the protective layer is removed, the cavitation process develops by grain boundary erosion, leading to the expulsion of grains from the surface. The gas nitrided Ti-6Al-4V alloy, forming a TixN surface layer, proved to be a better solution to improve the cavitation erosion resistance, compared to the annealed and nitrided and heat treated state, respectively. The analysis of the mean depth of erosion rate at 165 min cavitation time showed an improvement of the cavitation erosion resistance of the nitrided samples of up to 77% higher compared to the one of the annealed samples.
Cavitation erosion and wear behaviour of a boron cast iron cylinder liner under bio-fuel conditions
The use of renewable bio-fuel in internal combustion engines is the trend for the near future. However, it is easy to affect the cylinder liner due to the cavitation of the fuels. This study shows definite evidence that the cavitation erosion affects the tribological behaviour of the boron cast iron cylinder liner. The results indicate that the amount of both adsorbed lubricating film and tribo-film on the worn surfaces of the boron cast iron decreased with an increase in cavitation time, which is the direct reason for the increase of the friction coefficient and wear loss of the cylinder liner.
Nitriding of titanium in an r.f. discharge II: Effect of the addition of hydrogen to nitrogen on nitriding
Abstract The nitriding of titanium in a nitrogen or a nitrogen-hydrogen plasma prepared using an r.f. discharge was studied. The reaction kinetics obey a general relationship Δ 2 + AΔw = B ( t + τ ) The addition of hydrogen to the nitrogen plasma increased the weight gain. Electron spectroscopy for chemical analysis showed that N 1s based on the N—H bond and Si 2s electrons were present on the surface of the nitrided titanium. The effect of the addition of hydrogen to the nitrogen plasma is discussed in the light of the results of plasma diagnostics, such as emission spectroscopy, mass spectroscopy and the electrical double-probe technique, and the surface analysis.