The study of mechanical properties and corrosion resistance of Molybdenum coating and Aluminum coating using Thermal Spray method on stainless steel 316L

Thermal spray is one of the most common coating technologies used in oil and gas industries. This research applied two thermal spray methods, namely High Velocity Oxygen Fuel for Molybdenum coating and Electric Arc Spray for Aluminum coating to compare the coating formed by different methods on stainless steel 316L substrates. The thickness of the Mo coating ranges from 15-20μm, whereas Al coating has a thickness of 90-100μm. Coating characterization was assessed by using several testing methods, i.e. the Positive Material Identification (PMI) to identify the coating composition, the metallographic testing to observe the interface bonding of substrate and coating, hardness test and wear test to characterize the mechanical properties of the coating and salt spray test to identify the corrosion resistance. Base on the PMI testing, the Al coating show 98.15% wt of aluminum, while Mo coating contains only 9.832% wt molybdenum. The SEM/EDX applied in the metallographic test shows that the coating has a mechanical bond with the surface of the substrate, in which the Mo coating has a more effective bond than the Al coating on the substrate. The aluminum coating has a lower hardness value of 96 HB, while the Mo coating is approximately 106 HB. The wear test shows the Mo coating has a better wear resistance than the Al coating because the Mo coating has a smaller slit width of 0.375mm. The salt spray test shows the two types of coating did not affect the scratched area but there is significant discolouring that indicates the formation of uniform corrosion.