Study on the NHAP-PMEDM-milling process of 316 L steel

316 L steel-based human implants play an important role in the biomedical field. In order to address the problem of immune rejection of 316 L steel-based human implants and further improve the machining efficiency, the surface roughness (SR) and hydrophilicity of 316 L workpieces are improved by electrical discharge machining milling (EDM-milling) instead of die-sinking electrical discharge machining (EDM) and by the incorporation of nano hydroxyapatite (NHAP) powder into the dielectric. The effects of powder concentration of NHAP, reference voltage, peak current, pulse width, and pulse interval on the material removal rate (MRR), electrode wear rate (EWR), SR, and contact angle (CA) of 316 L workpiece processed by powder mixed EDM-milling with NHAP (NHAP-PMEDM-milling) are investigated by single-factor experiment, and comparisons are done with the powder mixed die-sinking electrical discharge machining with NHAP (NHAP-PMEDM). According to the results, the MRR, EWR, SR, and CA of 316 L by NHAP-PMEDM-milling are varied regularly with the variation of experiment parameters. The addition of NHAP powder into deionized water (DW) can reduce the CA of the surface of 316 L steel workpiece to a great extent, with a maximum reduction of 27.9%, while affecting MRR, EWR, and SR very little. In addition, NHAP-PMEDM-milling can increase MRR by 115.5% and reduce EWR, SR, and CA by 43.2%, 13.2%, and 15.9%, respectively, compared with NHAP-PMEDM.