Abstract
The elastic modulus is an important parameter that can be used to evaluate the properties of laser cladding coatings. However, methods of measuring the elastic modulus are destructive, time consuming, and inefficient. A nondestructive testing method based on a laser ultrasonic is presented. It can be used to measure the elastic modulus, but also to characterise the uniformity of the laser cladding coating. First, the surface microstructure of a laser cladding coating was observed using an optical microscope, and the elastic modulus of the coating was evaluated by a micro-indentation tester. The results showed that large dendrites with a small elastic modulus were mostly distributed in the joints, while the smaller equiaxed grains with a large elastic modulus were mainly distributed in the beads. However, there was no obvious difference between the joint and the bead in the energy spectrum measured by energy dispersive spectroscopy. Second, the surface wave signals were collected on the coating by laser ultrasonic, and the maximum amplitude and the delay time of surface waves of the scanning area were obtained. Through the relationship between the velocity of the surface wave and the elastic modulus, the distribution of the elastic modulus could be measured by a laser ultrasonic C-scan method. Comparison with the micro-indentation results shows that the laser ultrasonic is feasible for measuring the elastic modulus and characterising the uniformity of laser cladding coatings.
Published Version
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