Mechanical properties and oxidation formation of EB-PVD deposited Ni-Cr-Al alloy

摘要

Ni-20Cr-0.6Al(molar fraction, %) alloy sheet with 0.2 mm in thickness was deposited at 900°C from a target of Ni-Cr-Al alloy by EB-PVD. The grain size of as-deposited alloy was less than 100 nm. The mechanical properties of alloys were examined using room tensile tests. The ultimate tensile strength of as-deposited and annealed films was 780 MPa and 767 MPa, respectively. Investigation of fracture surfaces from samples reveals that brittle fracture takes place along boundaries of columnar crystals formed on the substrate side, while the equiaxed dimples are dominant on the evaporation side. Oxide formation of Ni-20Cr-0.6Al alloy after 100 h oxidation at 1 000°C in air was studied. The results indicate that a continuous and dense α-Al_2O_3 scale is formed after 100 h oxidation for as-deposited alloy, while a complex oxide scale, consisting of the outer oxide layer of Cr_2O_3, NiO and NiCr_2O_4 and the inner oxide layer of Al_2O_3, forms for annealed alloy.