Formation mechanism and quantitative analysis of pores in Al2O3–ZrO2 ceramic different structures by laser additive manufacturing

Pores is one of the most defects during laser additive manufacturing of ceramic material. In this paper, different structures of Al2O3–ZrO2 ceramics are deposited by using powder-feeding laser additive manufacturing. The ceramic structures can be simplified into three typical structures: linear-type, face-type and body-type structure. The formation mechanism and quantitative analysis of pores in different ceramic structures are studied. The pores of ceramic structure is mainly divided into four types: intercrystalline pore, interlayer pore, intralayer pore and shrinkage pore. In the linear-type structure, the number of pores with the interval 0–1000 μm2 accounts for 98.8%, while the area of pores with the interval above 104 μm2 accounts for 58.33%. The remelting rate of deposition layer has great influence on the pores. The Marangoni convection changed from inflow mode to outflow mode, which leads to that bubbles have easily escape from molten pool. In the face-type structure, the number and area of pores at the interval 0–1000 μm2 account for 98.96% and 51.62%, respectively. Overlap ratio is the key factor affecting pore. Under the effects of the Marangoni convection and the overlap of deposition layer, the irregular pores are easily formed in the bottom of overlap region of deposition layer. The pores characteristic in the body-type structure is similar to that in linear-type structure. Due to the laser remelting and overlap phenomenon, the thermal accumulation effect is more obvious in the short time interval and continuous deposition process of body-type structure. Thus, the gas of molten pool can be easily escaped. This study can provide the theoretical basis for the suppression of pores in ceramic laser additive manufacturing.