Energy analysis and quality evaluation of pulsed neodymium-doped yttrium aluminium garnet laser cladding ceramic-metal composite coating on aluminium alloys

Abstract

This research addressed an ‘energy threshold’ evaluation method for pulsed Nd-doped yttrium aluminium garnet (Nd-YAG) laser cladding. A high-power pulsed Nd-YAG laser was selected as the main equipment to investigate the performance of laser cladding ceramic-metal composite coating on Al alloys. Additionally, the basic characteristics of pulsed Nd-YAG laser for cladding processing were analysed. Three important system parameters of the pulsed Nd-YAG laser were isolated as the key factors that significantly affect cladding quality: Cladding speed, pulse width and laser power (pumping current). The experimental results were carefully analysed and evaluated. Firstly, the evaluation procedures included cladding track observation. The integrity of the tracks was used to judge whether the cladding was successful or inadequate. Secondly, the cross-section of the cladding layer was measured and examined. Three indexes of cladding quality (the thickness, the penetration depth and the shrinkage cavity area in the cladding layer) were analysed. From these evaluations, it was found that the pulse energy is the critical factor for pulsed Nd-YAG laser cladding. The research results also suggest that the minimum pulse energy Ep∗ may be adopted as the ‘energy threshold’ for continuously and successfully cladding the ceramic-metal composite on Al alloys.