Tribocorrosion behavior of nickel-aluminium bronze sliding against alumina under the lubrication by seawater with different halide concentrations

The tribocorrosion failure mechanism of nickel-aluminium bronze(NAB) in different halide concentrations of seawater was studied using a pin-on-disc tribometer that was modified to conduct in-situ electrochemical detection during the sliding process. It has been reported that high-halide-concentration seawater provided a good lubricating effect, and thus reduced the coefficient of friction and wear rate of NAB during the tribocorrosion process. However, the existence of halide ions corroded the passive film and hindered the repassivation of the damaged areas in the wear track, resulting in an increased corrosion rate. In addition, the morphology of the wear scar revealed the occurrence of abrasive, delamination, and adhesive wear of NAB in seawater. For the whole range of halide concentration values, a positive synergy between wear and corrosion was proven, and the quantification of this synergy was discussed in detail. The results show that the corrosionwear synergism was decreased with increasing halide concentration in seawater, and the corrosion-induced wear was dominant in the two synergistic components.

In-situ formation of layer-like Ag_(2)MoO_(4)induced by high-temperature oxidation and its effect on the self-lubricating properties of NiCoCrAlYTa/Ag/Mo coatings

Ag-Mo-O ternary oxide has attracted growing attention because of its potential as a solid lubricant at high temperatures.This work designs and prepares NiCoCrAlYTa/Ag/Mo composite coating,performed using high velocity oxy-fuel(HVOF)spraying technology.The environment temperature plays an important role in the microstructure and phases as well as lubricant properties of NiCoCrAlYTa/Ag/Mo coatings.When the environment temperature is above 600℃,the outer diffusion and oxidation of Ag and Mo lead to the formation of Ag2 MoO4 on the coating surface.Layer-like Ag2 MoO4 could form a continuous lubricant film at 800℃and consequently let the composite coating present the best tribological properties.Meanwhile,a small number of hard particles could play a good bearing role during friction and improve the tribological properties of the composite coating.

Effect of annealing treatment on microstructures,mechanical properties and cavitation erosion performance of high velocity oxy-fuel sprayed NiCoCrAlYTa coating

The mechanical parts serving in the marine environment are up against the dual damage of corrosion and cavitation erosion,so the Ni Co Cr Al YTa coating with excellent corrosion resistance is successfully prepared by high velocity oxy-fuel(HVOF)sprayed technology to protect the equipment from deterioration.The chemical composition and mechanical properties as well as the microstructure evolution of the coating before and after annealing treatment are studied.At the same time,the influence of annealing treatment on the corrosion and cavitation erosion behaviors of the coating is investigated,as well.The NiCoCrAlYTa coating mainly containsγ-Ni,β-Ni Al,andγ’-Ni3Al phases.During the deposition,the microcrystals or incomplete crystals generate in the interior of the coating because of the large temperature difference and impact force.Meanwhile,there is twin crystal structure in the as-spayed coating.After annealing treatment,the growth of grains and the segregation of reactive elements improve interface strength and inhibit the formation of micro-defects in the coating.The annealing temperature is of significance to the microstructure,mechanical properties,anti-corrosion and cavitation erosion resistance of the coating.This study provides a combined approach toward improving the corrosion and cavitation erosion resistance of NiCoCrAlYTa coatings.

Tribocorrosion properties of AISI 1045 and AISI 2205 steels in seawater: Synergistic interactions of wear and corrosion

Tribocorrosion denotes an irreversible material degradation for several metallic components used in corrosive environments,and it arises from the interplay between chemical,mechanical,and electrochemical processes.In this study,some investigation has been performed to compare the tribocorrosion behavior of AISI 1045 steel and AISI 2205 duplex stainless steel sliding against an alumina pin in seawater.The lowering in the open circuit potential(OCP)of AISI 2205 during the tribocorrosion demonstrates that its protective passive film was damaged by wear and resulted in a wear‐accelerated corrosion in the wear track.However,sliding was found to accelerate the corrosion of the unworn areas for AISI 1045,leading to an anodic shift of the OCP.Moreover,the total material loss increased with an increase in the applied potential for both materials.It was revealed that AISI 1045 was more sensitive to corrosion under sliding than AISI 2205.Therefore,pure corrosion loss and corrosion‐induced wear constituted the primary reasons for the degradation of AISI 1045 at applied anodic potentials.