Slurry jet erosion performance of high-velocity flame-sprayed nano mixed Ni-40Al₂O₃ coating in aggressive environment

Abstract

Hydro turbine components are subjected to severe erosion especially during the rainy season in the Himalayan region. To protect the CA6NM turbine steel, an attempt has been made to develop the Ni-40Al2O3 composite coating using a high-velocity flame spray process. To lower the porosity, the coating was developed by mixing two different sizes (viz. micron and nano) of alumina (Al2O3) reinforcement with 60 wt.% Ni as the base powder. The characterization of the as-sprayed coating was done by scanning electron microscopy/energy dispersive X-ray spectroscopy, and PANalytical X-ray diffraction technique, whereas mechanical characterization was done for the evaluation of microhardness, bond strength, and surface roughness. The performance of the developed coating was compared with uncoated steel on slurry jet erosion test rig under accelerated conditions by varying the three parameters, viz. slurry concentration, erodent size, and impact velocity. Ni-40Al2O3 coating was found to be effective for minimizing the erosion rate in comparison with the uncoated steel. Scanning electron microscopy of eroded coatings mainly reveals the brittle type of signature on the coating.

Study and comparison of wear behaviour of Ni-Al2O3 coatings deposited by hot and cold spray

“…The cold sprayed and hot sprayed coatings were found to have the major phases such as Ni, NiAl, and ϒ-Al 2 O 3 while the minor phases such as Ni 3 Al, NiAl 2 O 4 andAl 2 O 3 (δ, θ and α forms) were observed with a negligible amount of NiO phase. All the phases indicated by the XRD curves are in agreement with the literature found elsewhere [39][40][41]. It shows no evidence of any new phase.…”

“…Many researchers have worked using Ni or Cr-based coatings with different thermal spray techniques and evaluated their erosion-corrosion resistance properties [29][30][31][32][33][34][35]. The literature is rarely available related to the wear resistance performance of these coatings [36][37][38][39][40][41][42]. So there is a desperate requirement to conduct the study of wear resistance performance of these cermet coatings used in high-temperature applications.…”

Micro and nano ceramic-metal composite coatings by thermal spray process to control slurry erosion in hydroturbine steel: an overview

“…The model has been proposed by the author to demonstrate the change in surface roughness and porosity of the Ni-Al 2 O 3 coatings. Sharma et al [55] conducted an experiment for studying the erosion performance of multi-dimensional nickel matrix based alumina nanostructured coating deposited on CA6NM steel. Author opined that the nickel matrix reinforced with micron-nano reinforced coating material is very effective in the metigation of the eosion problem.…”

Erosion behaviour of HVOF sprayed Alloy718-nano Al2O3 composite coatings on grey cast iron at elevated temperature conditions

“…Whereas, some impact sites along with cracks and pullout were also observed at 90°impact angle as shown in figure 12(b). During erosion tests conducted at a 30°impact angle, ploughing and abrasion marks can be seen along with the plastically deformed and strain-hardened material (lip), as seen in figure 12(a) [40]. In the worn-out surface of 10N coated specimens, the ploughing and plastic deformation reveals the tendency of failure as a ductile mode of erosion at a 30°angle of impact [41].…”