Growth mechanism and mechanical property of laminar iridium coating by electrodeposition

Iridium coatings were prepared on rhenium coated graphite by electrodeposition. The Ir coatings were annealed at 1250 degrees C, 1600 degrees C and 1950 degrees C for 7.5 h, respectively. Growth mechanism and mechanical properties of the h. coatings were investigated. Results showed that the as-received Ir coatings had thickness of about 0.25 mm and characterized as laminar columnar grain structure, which resulted from using higher and lower current densities (-50 mA/cm(2) and -20 mA/cm(2)) alternately. Annealing temperature affected mechanical properties of the Ir coating by changing residual stress, defects and grain size of the coating. The average tensile strength of the asreceived, 1250 degrees C-annealed, 1600 degrees C-annealed, 1950 degrees C-annealed (in vacuum) Ir coating and 1950 degrees C-annealed (in hydrogen) was about 250 MPa, 270 MPa, 234 MPa, 117 MPa and 91 MPa respectively. (C) 2015 Elsevier Ltd. All rights reserved.