Obtenção e caracterização de revestimento de liga de alumínio quasicristalina aproximante por aspersão térmica por chama

Abstract

The thermal barrier coatings (TBC) are coatings that seek to change the surface properties of components through the use of materials which have low thermal conductivity, high melting point and good mechanical properties at high temperatures. Therefore, looking for improve efficiency and reduce maintenance costs, these coatings are applied mainly in gas turbines and diesel engines. The quasicrystals, duo to their properties of low thermal conductivity and a thermal expansion coefficient that is close to the most common metals substrates, are good candidates to replace the usual ceramics that often fail prematurely in the coating due to differences in thermal expansion coefficient between the coating and the metal substrate. Thus, this term paper shows the analysis of the coatings obtained by thermal spraying method of atomized powders Al71Co13Fe8Cr8 alloy, a quasicrystalline verging, with the physical and transport properties presented by the quasicrystalline phase, on substrates of a steel 1020 alloy and an aluminum 4032 alloy. Moreover, it was also studied the application of an UltraBond 25000 alloy’s bond coat to study an improvement in adhesion. In the analysis of the microstructure the coating showed some porosity and concentration of oxides. In the XRD the expected phases Al5Co2 and Al13Co4 were found, besides the Al3,21Si0,47, nickel-fcc and aluminum-fcc phases. With the exception of the sample with substrate of the aluminum 4032 alloy without UltraBond 25000 alloy’s bond coat, the others samples presented ideal adherence in the test of folding. Regarding the Vickers microhardness, the coating presented the highest values expected, even higher than the literature. In the tensile adhesion test it was verified the improvement in adhesion with the use of the UltraBond 25000 alloy’s bond coat. The relative thermal insulation capacity of the coating was confirmed by thermal tests.