IMPACTS OF MATERIAL AND MACHINE ON THE VARIATION OF ADDITIVELY MANUFACTURED COOLING CHANNELS

Abstract While additive manufacturing (AM) can reduce component development time and create unique cooling designs, the AM process also introduces sources of variability, such as the selection of machine and material. Because of these sources, variations in a part's geometrical accuracy and surface roughness can occur, especially for small internal features that are difficult to post-process. This study investigates how the selection of machine and material in the AM process influences variations in surface quality and geometric deviation. Two microscale cooling geometries were tested: wavy channels and diamond pin fins. Test coupons were fabricated with five machines and four materials using process parameters recommended by the manufacturers. The as-built geometry was measured non-destructively with computed tomography scans. To evaluate surface roughness, the coupons were cut-open and examined using a laser microscope. Results indicated that material and machine contribute to producing different roughness levels and very different surface morphologies. Geometric analysis revealed that while the hydraulic diameter of all coupons was well captured, pin cross sections varied considerably. Cooling performance was investigated by experimentally measuring friction factor and heat transfer. The variations in surface morphology as a function of material and machine resulted in heat transfer fluctuated up to 50% for wavy channel coupons and 26% for coupons with pin fin arrays. Increased arithmetic mean surface roughness led to increased heat transfer and pressure drop; however, a secondary driver for performance of wavy channels was the roughness morphology, which was descibed using skewness and kurtosis.