Cavitation erosion performance of CrAlYN/CrN nanoscale multilayer coatings deposited on Ti6Al4V by HIPIMS

Abstract

Water droplet erosion (WDE) protection of Ti6Al4V turbofan blades is of paramount importance to the aviation industry. A novel CrAlYN/CrN nanoscale multilayer coating deposited by the HIPIMS technique was evaluated as a potential candidate for this application. Literature suggests a strong correlation in performance ranking under WDE and cavitation erosion (CE) tests. Hence, the WDE performance of the CrAlYN/CrN coating on Ti6Al4V was investigated with an ultrasonic cavitation device. The results show excellent adhesion and superior erosion resistance of the CrAlYN/CrN coating (erosion rate lower by a factor of 14 compared to the bare Ti6Al4V substrate) and compared to coatings reported in the literature with spallation as their main erosion mechanism. Cross-sectional FIB studies revealed formation of substrate cracks underneath 2 the coating when CE generated stresses exceeded the fatigue strength of the Ti6Al4V alloy.The interfaces of the nanoscale multilayers protected the substrate by forming an effective barrier against shock waves, delayed fatigue crack formation, deflected and arrested any cracks formed impeding the overall coating damage. The research shows that the CE resistance is influenced by the coating's texture and elastic properties, (Young's modulus).The paper discusses the erosion mechanisms of the coating and the excellent CE protection it offers.

Resistance of PVD Coatings to Erosive and Wear Processes: A Review

“…The decrease in cumulative volume loss caused by PVD coating was noted in many works, e.g., in References [77,[80][81][82]. However, some studies showed that the deposition of a hard PVD coating does not always provide extended incubation time and/or improved resistance to cavitation damage [46,67,79,83]. The 2.7 µm thick TiN coating deposited on Ti6Al4V alloy had no incubation period and a very high erosion rate compared to the uncoated substrate (Figure 4a) [67].…”

“…The phenomenon of cavitation erosion consists in the degradation of the material surface as a result of multiple impacts of micro-jets formed during the implosions of cavitation bubbles. Cavitation erosion resistance of materials is tested using mainly ultrasonic devices compliant with the ASTM G-32 standard (Figure 1) [30,53,[65][66][67][68][69]. The ASTM G-32 standard allows performing tests in the direct and indirect methods (Figure 1).…”

“…However, some studies showed that the deposition of a hard PVD coating does not always provide extended incubation time and/or improved resistance to cavitation damage [46,67,79,83]. The 2.7 µm thick TiN coating deposited on Ti6Al4V alloy had no incubation period and a very high erosion rate compared to the uncoated substrate (Figure 4a) [67]. Additionally, the 3.7 µm thick TiN coating deposited at 500 • C on austenitic steel decreased the resistance to cavitation erosion [83].…”

Damage Development on the Surface of Nickel Coating in the Initial Period of Erosion

“…Nevertheless, the differences in the corrosion resistance of the coating and the substrate, as well as the decrease in hardness and modulus of elasticity under cyclic loading conditions, affect the development of damage. Although the high hardness of the coating protects against cavitation degradation, a large difference in the hardness of the coating and the substrate can lead to accelerated erosion through delamination and removal of the coating [ 28 , 46 , 47 ].…”

Effect of Heat Treatment on the Cavitation Erosion Performance of WC–12Co Coatings

“…The different performance of the five coatings may be caused by the following two factors. Firstly, the micro defects of the coatings such as pores, cracks, unmelted, or semi-melted particles play a negative role in cavitation erosion process [31][32][33][34]. It is clearly observed from Figure 9 that microcracks, pores, and unmelted that particles existed in the surface of the HT 1100 coating before cavitation erosion.…”