Growth mechanism and mechanical property of laminar iridium coating by electrodeposition

•Thick and laminar Ir coatings were prepared by electrodeposition.•The laminar microstructure of the Ir coating was determined by cathodic current.•Heat treatment affected the residual stress, grain size and defects of the Ir coating.•The Ir coatings annealed at 1250 °C had the highest strength of about 270 MPa.

Iridium coatings were prepared on rhenium coated graphite by electrodeposition. The Ir coatings were annealed at 1250 °C, 1600 °C and 1950 °C for 7.5 h, respectively. Growth mechanism and mechanical properties of the Ir 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/cm2 and − 20 mA/cm2) 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 as-received, 1250 °C-annealed, 1600 °C-annealed, 1950 °C-annealed (in vacuum) Ir coating and 1950 °C-annealed (in hydrogen) was about 250 MPa, 270 MPa, 234 MPa, 117 MPa and 91 MPa respectively.