Product Code: ICAL07_1706

Laser Cladding of Al-Si/Sic Composite Coatings: Microstructure and Abrasive Wear Behavior
Authors:
Ramasamy Anandkumar, Instituto Superior Tecnico; Lisboa Portugal
Amelia Almeida, Instituto Superior Tecnico; Lisbon Portugal
Rui Vilar, Instituto Superior Tecnico; Lisboa Portugal
Vaclav Ocelik, University of Groningen; Groningen Netherlands
Jeff De Hosson, University of Groningen; Groningen Netherlands
Presented at ICALEO 2007

Coatings of a composite material consisting of an Al-Si matrix reinforced with SiC particles were produced by laser cladding on cast UNS 356 alloy substrates. The influence of processing parameters on the microstructure and abrasive wear resistance of the coatings was studied. For an interaction time of 0.08 s and a power density of 330 MW/m2, corresponding to a specific energy of 26 MJ/m2, the interaction between SiC and liquid Al is limited and the reinforcement particles remain essentially undissolved. The coatings microstructure is formed of SiC particles dispersed in a matrix consisting of primary α-Al dendrites and interdendritic α-Al+Si eutectic. For interaction times of 0.3 and 0.45 s and a power density of 193 MW/m2, corresponding to specific energies of 58 and 87 MJ/m2, SiC reacts with molten Al and partially dissolves. The resulting microstructure consists of undissolved SiC particles, found mainly at the bottom of the clad tracks, where the maximum temperature reached during processing is lower, and Al4SiC4 and Si particles dispersed in a matrix of α-Al+Si eutectic. The coatings prepared with high specific energy present a hardness of 250 HV and an abrasive wear rate in tests with SiC as abrasive of 1.7x10^-4 mm3/m, while those produced with low specific energy present a hardness of 120 HV and a wear rate of 0.43 x10^-4 mm3/m. These results show that Al4SiC4 and Si increase the hardness of the material by dispersion hardening but do not contribute to its abrasive wear resistance, because they are softer than the abrasive particles, and confirm that the parameters used to prepare Al-Si-SiC composite coatings by laser cladding must be selected so that only minimal reactions occur between SiC and molten Al.