The Study On The Microstructure And Properties Of Heat-resistant Coatings Deposited By Arc Spraying On Cast Iron

Arc spraying is an inexpensive thermal spray deposition process, and arc-spray coatings are normally denser and stronger than their equivalent combustion-spray coatings. Low running costs, low oxide contents, high spray rates and efficiency make this a good process for spraying large areas. But its application is limited severely for its low thermal fatigue resistance. So it is very important for the application of arc spraying and heat-resistant cast iron to develop a new arc-sprayed process to make the heat-resistant coatings with fine thermal fatigue behavior deposited on cast iron.At the present work, aluminizing and sintering treatment have been developed to improve the properties of arc-sprayed coatings. The influence of aluminizing and sintering treatment on the thermal fatigue behavior of heat-resistant coatings has been studied in this article. The coatings, all with outer coatings of 18-8 stainless steel but with different inner layers, were made by arc spraying, aluminizing and sintering on cast iron. The microstructure and characterization of the coatings were studied by optical microscope, scanning electron microscope, laser scanning confocal microscope, energy dispersive X-ray spectroscopy and X-ray diffraction. The thermal fatigue behavior of the coatings was evaluated by thermal fatigue tests, and the bond strength was measured by tensile tests.The results show: the thermal fatigue behavior of the coatings was greatly improved by aluminizing and sintering; the bond strength of coatings were also improved greatly; aluminizing time, sintering time and temperature should be controlled well; insofar as materials for inner coatings are concerned, FeCrAl is better than aluminum.