Effect of surface conditioning on the flowability of Ti6Al7Nb powder for selective laser melting applications

Rheological behavior of β-Ti and NiTi powders produced by atomization for SLM production of open porous orthopedic implants

“…Each powder aimed for SLM applications must satisfy this requirement and if not met should undergo study on the improvement of its flow behavior. Similar studies have already been carried out for Ti-6Al-7Nb powder by T. Marcu et al resulting in the delivery of powder with very good flow properties [13].…”

“…Indeed, hot argon gas used in the plasma atomization process allows particles to stay for a longer period at high temperature which results in a smoother particle surface than in a gas atomization process [21]. In the same sense T. Marcu et al stated that thermal treatment of Ti-6Al-7Nb powder at 500°C during 1 h in air improves its flowability by the formation of an Al 2 O 3 surface layer on the particles [13]. Fig.…”

“…10). Therefore the improvement of flowability for the heat treated TiNb-1 powder cannot only be attributed to a surface smoothening or to the formation of a thicker oxide layer for the TiNb-1 sample heat treated in air [13] and a change in surface chemical composition [39]. Another reason for the differences in flowability could be the formation of a suboxide within the oxide film in addition to abundant TiO 2 [40] and could also be the conversion of amorphous anatase to rutile at the annealing temperatures in the range of 500-1000°C [41,42].…”

“…However, owing to the high cost of this technology priority was given to a heat treatment approach. Thus, TiNb-1 powder was exposed to a heat treatment (at 600°C for 1 h) in air and to the same heat treatment but in argon atmosphere [13]. The heat treatment in air might induce formation of a thicker oxide layer on the particle surface and a slight smoothing of the particle surface but most likely will also result in diffusion of interstitial impurity atoms such as O and N, which might compromise quality when high strength and ductility of fabricated parts are required [38].…”

“…Heat treatment of TiNb-1 sample was carried out in a Carbolite general purpose box furnace in air at 600°C for 1 h according to the procedure of Marcu et al [13]. TiNb-1 powder was also exposed to the same heat treatment in a Carbolite horizontal tube furnace with a protective argon atmosphere to avoid diffusion of interstitial atoms such as O and N. Particle size distribution was measured by a laser diffraction particle size analyzer Mastersizer (Malvern Instruments Ltd., Malvern, UK) in a dispersed state in liquid ("wet" Laser Diffraction Spectrometry, LDS-W method); number of measurements, n = 1.…”