Investigation of the effect of hydroxyapatite (HA) powder added to dielectric liquid in electro erosion processing on biofilm formation and workability performance

The aim of this research is to investigate the machinability, cellular proliferation and interaction of different parameters with bacteria on the Ti6Al4V alloy surface with hydroxyapatite (HA) and hexagonal boron nitride (hBN) powder-added electrical discharge machining using the Taguchi technique. In this context, X-ray diffraction (XRD), optical and scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), surface roughness (SR), contact angle measurements were used to characterise the structural and morphological properties of the samples on the surface and subsurface. Powder additives were deposited on the surfaces of the samples with different processing parameters during the EDM (Electro Erosion Machining) process, and XRD and EDS results revealed the presence of HA and hBN phases. In this regard, the surface roughness values varied between 2.03 μm and 3.97 μm on average, depending on the discharge current, pulse duration and the change of powder ratios added to the dielectric liquid. In addition, while the cratered structures formed on the surfaces of the samples processed after EDM reduce the surface wettability, the best wettability is the surface with a discharge current of 9 A, a pulse duration of 200 μs and a surface with 15 g/l hydroxyapatite (HA) powder added. In order to correlate processing performance with the effect of added dust concentrations on biofilm, cellular adhesion and proliferation were examined with Staphylococcus aureus bacterial strain at 2, 4, and 6 h. This showed that a 5 g powder additive promoted cellular activity growth, while a 10 g concentration inhibited it, except for HA/hBN particles. Extending exposure to 15 g further confirmed biofilm formation, highlighting the complexity of bacteria adhesion