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.