C. Li

Surface integrity and corrosion performance of biomedical magnesium-calcium alloy processed by hybrid dry cutting-finish burnishing

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive orthopedic biomaterial compared to permanent metallic alloys. However, the critical issue is that MgCa alloy corrodes too fast in the human organism. Compared to dry cutting, the synergistic dry cutting-finish burnishing can significantly improve corrosion performance of MgCa0.8 (wt%) alloy by producing a superior surface integrity including good surface finish, high compressive hook-shaped residual stress profile, extended strain hardening in subsurface, and little change of grain size. A FEA model was developed to understand the plastic deformation of MgCa materials during burnishing process. The measured polarization curves, surface micrographs, and element distributions of the corroded surfaces by burnishing show an increasing and uniform corrosion resistance to simulated body fluid.

Surface integrity of Inconel 718 by hybrid selective laser melting and milling

ABSTRACT While selective laser melting (SLM) offers design freedom of metal parts with much less material consumption, there exist several limitations, including high surface roughness, low-dimensional accuracy, and high tensile residual stresses. To make functional parts with high form accuracy and superior surface integrity, an as-SLM part needs finishing to remove the deposited surface material. The integration of machining and SLM creates a hybrid manufacturing route to overcome the inherited limitations of SLM. However, little study has been done to characterise surface integrity of an as-SLM part followed by machining (e.g. hybrid SLM-milling). In this paper, surface, integrity including surface roughness, microstructure, and microhardness, have been characterised for IN718 samples processed by the hybrid process. It has been found that microhardness varies with the scan direction and the use of coolant in the subsequent milling, and surface integrity can be significantly improved by the hybrid SLM-milling route.