Abstract

Aerosol Deposition (AD) is a novel deposition process for solid-state material deposition at ambient temperature. AD is an excellent candidate for producing ceramic composite coatings due to the even distribution of reinforcing material inside the ceramic matrix.
In this work, AD has been used to create an alumina coating containing 2 weight-percent graphene nanoplatelets (GNPs). In order to prepare this composite powder, alumina and GNPs were milled in cyclohexane by high-energy milling. This powder was then used as the feedstock for aerosol deposition using an in-house vacuum apparatus. Various relevant characteristics, such as stand-off distance, carrier gas, particle size distribution, and nozzle shape, have been examined in order to obtain the operating condition for generating coatings. Successful coatings were achieved on stainless steel substrates for both alumina and alumina-GNP powders after modifying several of the spray parameters.
Studies using Raman spectroscopy have shown that the presence of GNPs in composite feedstock is significant. The coefficient of friction of the composite coatings and pure alumina deposits have both been measured using the micro scratch adhesion test. In tests of micro scratch adhesion with forces ranging from 0.3 to 30 N, it was discovered that the coefficient of friction of the alumina/GNP composite was lower than that of the comparable pure alumina covering. The test findings show that, in comparison to pure alumina deposition, the coefficient of friction in the alumina + GNP coating was reduced by the exfoliation of graphene layers from GNPs. The alumina coating experienced brittle spalling and delamination of the coating from the substrate at the interface, whereas the alumina + GNP coating showed no evidence of adhesion failure. The transition to the serious wear regime occurred between 5.7 and 30 N in progressive load scratch testing for the pure alumina coating, while the initial yield point of the alumina + GNP coating was observed at 7.5 N.SEM was used to characterize the microstructure of this graphene/alumina film.