Development of a processing window for Ti6Al4V in LPBF: balancing hardness and surface integrity

Purpose This research aims to develop a processing window for manufacturing Ti6Al4V using laser powder bed fusion (LPBF). By analysing the interrelationship between volumetric energy density (VED) and the four key LPBF process parameters – laser power, scan speed, scan spacing and layer height – this study identifies the optimal parameter set to manufacture Ti6Al4V with high hardness without compromising the surface quality. Design/methodology/approach A Taguchi L9 was used to generate nine sets of process parameters to fabricate Ti6Al4V samples using the RenAM 500E printing machine. The process parameters used were laser power between 180 and 220 W, scan speed between 1000 and 1500 mm/s, scan spacing between 55 and 65 µm, and a fixed layer height of 40 µm. All samples underwent annealing at 935 °C for 8h to relieve residual stresses, with a controlled heating rate of 5 °C/min and a cooling rate of 0.6 °C/min. The hardness and microstructure of samples were analysed to determine the optimal LPBF process parameters. Findings The optimized LPBF parameters were identified as a laser power of 180W, scan speed of 1200 mm/s, scan spacing of 60 µm and a layer height of 40 µm. A validation experiment confirmed a 3% increase in hardness, from 359 to 370 HV, without degrading the surface roughness (9.31 µm). Originality/value This research provides a comprehensive analysis of key LPBF process parameters to establish a processing window for achieving high hardness in Ti6Al4V while maintaining the surface quality. The study’s findings offer valuable insights in enhancing the performance of commercially produced Ti6Al4V products, such as heat exchangers and biomedical implants.