Laser-clad Al-Matrix coatings reinforced with icosahedral quasicrystals obtained using Al-Cu-Fe–Cr decagonal quasicrystalline powders on Al substrates

Coating fabrication using laser cladding process is a versatile method for producing functional surfaces that can be tailored to present enhanced physical and chemical properties. The high cooling rates that are experienced by the materials being deposited favor the formation of refined metastable phases. Among these, the formation of refined icosahedral quasicrystals, embedded in an Al matrix, is an especially desirable surface microstructure, due to its low friction coefficient and high hardness, which are essential for applications demanding resistance to scratches and wear. It has been recently shown that decagonal quasicrystals forming in Al-Cu-Fe–Cr alloys can transform into icosahedral quasicrystals when rapid solidification methods are applied. This trend is further intensified when the Al concentration is increased. In this sense, the present work aims at applying the laser cladding process using a pre-alloyed Al₆₇Cu₂₀Fe₅Cr₈ (%at.) and commercial purity Al powders to study the effect of the rapid cooling rates and Al dilution, that the pre-alloyed powders will be subjected to, on the nature of the quasicrystalline phase formed. In addition, this work also focuses on obtaining adequate laser cladding parameters that yield high quality coatings on the Al substrate. This work shows that using a mixture of Al-Cu-Fe–Cr and pure Al powders resulted in a suitable dilution depth, which led to a homogeneous distribution of the reinforcing particles in the Al matrix. On the other hand, the cladded surfaces produced with only the Al-Cu-Fe–Cr powder resulted in coatings with almost no dilution into the Al substrate and, consequently, poor interfacial microstructure quality. It is also shown that although the pre-alloyed powder consisted mostly of decagonal quasicrystals, when this alloy was diluted to more Al-concentrated compositions and subjected to the fast solidification conditions of the laser cladding process, the quasicrystals formed belong to the icosahedral structure. The laser-clad track with the highest quality was obtained with the Al-Cu-Fe–Cr + Al powder mixture, subjected to a laser power of 200 W, which resulted in a microstructure composed of fine and well-distributed icosahedral quasicrystalline particles dispersed in the Al matrix. This laser-clad track presented the highest microhardness values among all the tested samples, about 251 kgf/mm², substantially higher than the microhardness of 54 kgf/mm² from the Al substrate.