Evaluation of modulus of elasticity, nano-hardness and fracture toughness of TiB2-TiC-Al2O3 composite coating developed by SHS and laser cladding

Modulus of elasticity (E) and nano-hardness (H) of the composite TiB2-TiC-Al2O3 coating deposited on AISI 1020 steel by combined self-propagating high-temperature synthesis (SHS) and laser cladding process have been measured from load-displacement curves, resulting from nano-indentation testing. Fracture toughness (K-IC) of the coatings has been evaluated from the indentation method. A qualitative evaluation of interfacial strength between coating and substrate material was also performed by indentation method. Results indicated elastic modulus and fracture toughness of the composite coatings are in the range of 230-280 GPa and 5.46-6.12 MPa m(1/2) those are respectively lower and higher than those of the individual constituent ceramics. Nano-hardness of the coating microstructure obtained was in the range of 16-22 GPa and was found to vary depending on the laser-processing parameter adopted. Indentation taken with high load at the coating-substrate interface indicated a strong interfacial bond between coating and steel substrate. An attempt has been made to co-relate the wear rate of the coating with H/E ratio. (C) 2011 Elsevier B.V. All rights reserved.