Effects of ceramic material in laser-directed energy deposition of titanium/ ceramic functionally graded materials

The titanium/ceramic functionally graded materials (FGMs) have much higher wear resistance than traditional titanium alloys, while cracks are easily formed during the manufacturing process. The zirconia-toughened alumina (ZTA) was adopted to suppress the crack and improve the performances in the laser-directed energy deposition (L-DED) of TC4/ZTA FGMs. The mechanisms influencing the microstructure, hardness, and friction wear properties of the ZTA were investigated. The interfacial reactions and solid-state phase transformation during the L-DED process formed TiAl2O5 compounds and nanoscale yttria-stabilized tetragonal zirconia (YSZ) particles in the ZTA-deposited layer, where the & beta; and lamellar martensitic secondary & alpha;' phases were increased by Zr. The nano-YSZ particles refined the grains in the ZTA-deposited layer by promoting heterogeneous nucleation and inhibiting grain growth, thereby causing a columnar-to-equiaxed transition. The hardness and friction wear properties increased with an increasing ZTA concentration, which is caused by the fine grain and Orowan strengthening effects of the nano-YSZ particles. Additionally, the better ductility and lower mismatch in the coefficient of thermal expansion of ZTA compared with Al2O3 ceramic were beneficial for crack suppression.

Automated summary

The use of zirconia-toughened alumina (ZTA) can improve the performance of titanium/ceramic functionally graded materials (FGMs) and suppress cracks during the manufacturing process.