Gaussian and circular oscillating laser directed energy deposition of WC/NiCu composites

Abstract

In the realm of laser directed energy deposition (L-DED), the standard procedure typically using a Gaussian laser as the primary energy source. However, this well-established technique also has limitations as it generates considerable temperature gradients and residual stresses throughout the manufacturing process, resulting in notable deformation and cracking. To overcome these limitations, this study advocates for the replacement of the Gaussian laser with a circular oscillating laser. NiCu alloys and 16 wt% WC/NiCu composites were manufactured using the Gaussian laser and the circular oscillating laser deposition equipment. The results of this study reveal that the circular oscillating laser methodology exerts a pronounced agitation effect on the melt pool, thus hindering the formation of columnar dendrites and promoting the emergence of more nucleation sites for the growth of equiaxed dendrites. This method effectively refines the grains by reducing the temperature gradient of the melt pool and increasing the cooling rate. The average grain size of NiCu alloy manufactured using the circular oscillating laser is reduced by 19.5% compared to that manufactured using the Gaussian laser. The high temperature generated by laser and melt pool caused partial decomposition of WC into W and C, leading to the formation of W2C hard phases between the dendrites. Additionally, the unmelted WC particles were uniformly dispersed throughout the composites, which hindered the growth of columnar dendrites and refined the grains. Compared to the composites manufactured using the Gaussian laser, the composites manufactured using the circular oscillating laser exhibit an average microhardness increase of 15% and 11.1%, and a 76.5% and 22.2% decrease in wear rate, respectively. Composites containing 16 wt% WC manufactured using the Gaussian laser exhibit the best corrosion resistance.