Macro to Atomic Scale Characterization of 3 mol% Yttria-Stabilized Tetragonal Zirconia Polycrystalline (3Y-TZP) Ceramics for Welding Pin Applications

This study aims to develop a zirconia-based ceramic with high mechanical properties for welding pin applications. 3 mol% yttria-stabilized tetragonal zirconia polycrystalline (3Y-TZP) nanopowders were synthesized by the hydrothermal method. According to the powder characteristics, the obtained powders only consisted of t-ZrO2 grains with high surface area (107 +/- 1.1 m(2)/g) and nano-sized individuals (7.2 +/- 0.2 nm average) as well as Y0.05ZrO1.5 at % chemical composition. The 3Y-TZP nanopowders were densified up to 99.10 +/- 0.1% relative density by pressureless sintering at 1500 degrees C for 2 h. Crystalline phases were determined as 73.5 +/- 1 vol.% t-ZrO2 and 26.5 +/- 1 vol.% m-ZrO2 in the sintered body using X-ray diffraction (XRD) analysis. Vickers hardness and indentation fracture toughness values were measured as 9.5 +/- 0.4 GPa and 15.17 +/- 0.2 MPa center dot m(1/2) in 3Y-TZP sintered ceramics(,) respectively. Scanning electron microscopy (SEM) observations showed homogeneous microstructure with submicron grains (780 +/- 5 nm) in sintered samples. Aberration-corrected scanning transmission electron microscopy (AbC-STEM) revealed the presence of t-ZrO2 to m-ZrO2 phase transformation in twinning grains giving rise to high fracture toughness in 3Y-TZP ceramics. As an end-product, ceramic welding pins were produced from hydrothermally synthesized 3Y-TZP nanopowders. They withstood the 300,000.00 +/- 5000.00 welded nuts in the performance test. This makes the 3Y-TZP ceramics an outstanding material in the projection nut welding process.