Understanding the surface integrity of laser surface engineered tungsten carbide

AbstractThe study investigated the effect of fibre laser processing (1060 nm, 240-ns pulse duration) on the surface integrity of tungsten carbide (WC). The induced surface damage ranged from crack formation, porosity, balling, to spherical pores; the severity and presence of each were dependent on the laser parameters selected. The influence of fluence (0.05–0.20 J/cm2), frequency (5–100 kHz), feed speed (250–2500 mm/s) and hatch distance (0.02–0.06 mm) on 2D and 3D surface roughness were analysed using the Taguchi technique. Fluence, frequency, and the interaction effect of these were the most influential factors on the surface integrity; from this a linear model was generated to predict the surface roughness. The model performed best at moderate to medium level of processing with an error between 1 and 10 %. The model failed to predict the material response as accurately at higher fluences with percentage errors between 15 and 36 %. In this study, a crack classification system and crack density variable were introduced to estimate the number of cracks and crack type within a 1-mm2 area size. Statistical analysis of variance (ANOVA) found that fluence (63.49%) and frequency (29.38%) had a significant effect on the crack density independently but not the interaction of both. The crack density was minimised at 0.149 J/cm2 and 52.5 kHz. To the author’s knowledge, for the first time, a quantitative analysis of the crack formation mechanism for brittle materials is proposed (post laser processing).