Microstructure and tribological properties of plasma sprayed Al-Cu-Fe quasicrystalline coatings after laser post-treatment processing

Abstract

This paper presents the results of the study on the effect of laser melting-solidification processing on the structure and tribological properties of plasma spray Al-Cu-Fe quasicrystalline alloy coatings. Dense and hard coatings were obtained by the laser post-treatment processing and the volume fraction of the icosahedral (i) phase was found to be dependent on the laser power and scanning velocity conditions. Using a parameter delta, defined as the ratio of the laser power P, to the scanning velocity v, i-phase was observed to form for low values of delta as a consequence of the high cooling rates. Furthermore, a correlation was worked out between the microhardness and the parameter delta. Owing to the microstructure modification, the laser post-treatment provided significant improvement to the tribological properties of the plasma sprayed Al-Cu-Fe QC coatings. The frictional behavior was found to be dependent on the constituent phases formed in the laser post-treated coatings. In particular, low values of the friction coefficient were recorded in the early stage of the test for coatings containing a high volume fraction of i-phase. However, owing to the brittleness of the i-phase, the difference of the frictional behavior was reduced after 150 cycles, and the friction coefficient for all laser post-treated coatings stabilized at a value which was approximately half that of the as-received plasma sprayed coatings. After laser post-treatment, the wear rate was significantly improved only for the coatings containing a high content of i-phase. (C) 2004 Elsevier B.V. All rights reserved.