Dynamic chemical polishing of millimeter-size channels heat exchanger made of Ti-6Al-4V alloy by Laser Powder Bed Fusion

Additive Manufacturing permits to build complex parts and optimize the thermal-hydraulic behavior of heat exchangers. However, post processing is often required to improve surface quality and reach the application’s specification. In the present study, an improved method of chemical polishing with forced circulation of the polishing fluid is developed. The impacts of this process on surface quality and dimensions of internal channels manufactured by Laser Powder Bed Fusion in Ti-6Al-4V, characteristic of heat exchangers, are evaluated. Samples built with two layer thicknesses (30 µm and 60 µm) are characterized in order to assess the impact of this parameter. In addition, two dimensional measurement methods (touch probe and tomography) are compared. Measurements carried out on as-built and polished samples show that the developed polishing process permits to reduce the mean surface roughness (Ra) of the internal surface of the channels, from 11 to 12 µm to 6–8 µm. The average erosion rate of the surface, calculated from the loss of mass of the samples, varies between 30 µm/min and 50 µm/min. • Dynamic chemical polishing of millimeter-size channels heat exchanger is carried out. • Unmelted powder particles trapped at the surface on as-built parts are removed after polishing. • Average surface roughness is improved by chemical polishing. • Erosion rate varies between 30 and 50 µm/min. • Measurement of channel diameter using a touch probe or derived from tomography data analysis, differ for raw surfaces but give comparable results for polished surfaces.