Pre-placed WC/Ni clad layers produced with a pulsed Nd:YAG laser via optical fibres

Abstract

Laser clad WC/Ni layers were produced on H13 tool steel substrates with a pulsed Nd:YAG laser and optical fibres using the pre-placed powder technique. The effects of parameter variation, such as laser pulse energy, beam profile, traverse speed and volume fraction of the reinforced WC particles, on clad layer formation and its properties were investigated. The microhardness of the clad layers was measured and the microstructure was characterised by optical and scanning electron microscopy and X-ray diffraction. The results show that relatively thick (>0.5 mm), fully dense and crack-free clad layers of WC/Ni can be formed on H13 substrates without any pre-heating. The results further show that the volume fraction of the reinforced WC particles is the dominant factor affecting most clad layer properties such as its porosity, microhardness and wear resistance. The greater the volume fraction of WC particles, the lower the porosity, the higher the microhardness and the higher the wear resistance of the clad layer. Average microhardness values of the matrix were as high as 800 HV and the pin-on-plate (reciprocating) wear tests showed the weight loss of the clad layers is substantially lower than that for the unclad substrate.