Densification behavior, microstructure evolution, and wear performance of selective laser melting processed commercially pure titanium

作者：Gu, Dongdong^*; Hagedorn, Yves-Christian; Meiners, Wilhelm; Meng, Guangbin; Batista, Rui Joao Santos; Wissenbach, Konrad; Poprawe, Reinhart

来源：Acta Materialia, 2012, 60(9): 3849-3860.

DOI：10.1016/j.actamat.2012.04.006

• Selective laser melting (SLM)
• Laser treatment
• Titanium
• Wear
• Microstructure

This work presents a comprehensive study of the densification behavior, phase and microstructure development, hardness and wear performance of commercially pure Ti parts processed by selective laser melting (SLM). An in-depth relationship between SLM process, microstructures, properties, and metallurgical mechanisms has been established. A combination of a low scan speed and attendant high laser energy density resulted in the formation of microscopic balling phenomenon and interlayer thermal microcracks, caused by a low liquid viscosity, a long liquid lifetime, and resultant elevated thermal stress. In contrast, using a high scan speed produced the disorderly liquid solidification front and considerably large balling, due to an elevated instability of the liquid induced by Marangoni convection. A narrow, feasible process window was accordingly determined to eliminate process defects and result in full densification. The phase constitutions and microstructural characteristics of SLM-processed Ti parts experienced a successive change on increasing the applied scan speeds: relatively coarsened lath-shaped alpha -> refined acicular-shaped martensitic alpha' -> further refined zigzag-structured martensitic alpha', due to the elevated thermal and kinetic undercooling and attendant solidification rate. The optimally prepared fully dense Ti parts had a very high hardness of 3.89 GPa, a reduced coefficient of friction of 0.98 and wear rate of 8.43 x 10(-4) mm(3) N-1 m(-1) in dry sliding wear tests. The formation of an adherent, plastically smeared tribolayer on the worn surface contributed to the enhancement of wear performance.

• 出版日期2012-5
• 单位南京航空航天大学