Interfacial microstructure and characterization of double-layer coatings on cast iron by arc spraying and sintering

The objective of the present work is to study the interfacial microstructure and characterization of double-layer coatings made by arc spraying and sintering and to obtain double-layer coatings with fine thermal fatigue behavior. The double-layer coatings, all with an outer coating of 18-8 stainless steel but with different inner coatings of aluminum or FeCrAl, were deposited by arc spraying on cast iron, after which test samples with the same coatings were sintered under different temperature and time conditions. The microstructure and characterization of the double-layer coatings were studied by optical microscope, SEM, LSCM, EDS and XRD. The thermal fatigue behavior of the coatings was evaluated by thermal fatigue tests, and the bond strength was measured by tensile tests. The results showed that the microstructure and characterization of the coatings were significantly affected by sintering, which yielded numerous regions with metallurgy bonding on the interfaces between coatings and substrates. As a result, the thermal fatigue behavior of the sintered coatings was greatly improved. Additionally, the double-layer coatings with FeCrAl inner coatings had better thermal fatigue behavior than those with aluminum inner coatings.