Tensile properties of HVOF sprayed Inconel 625 coatings subjected aqueous corrosion

Purpose - To examine the tensile properties of high velocity oxy-fuel (HVOF) sprayed Inconel 625 coating of steel substrate before and after the aqueous corrosion. Design/methodology/approach - Workpieces were cut from steel sheets. After chemical and ultrasonic cleaning, workpiece surfaces were sand blasted and HVOF sprayed Inconel 625 coated. The coated and un-coated surfaces were subjected to the aqueous corrosion tests for one and three weeks. After the completion of the corrosion tests, tensile properties of the workpieces were examined. Findings - The workpieces subjected to a three weeks static corrosion environment fail at a lower load than the untreated workpiece due to high stiffness. The defect sites in the coating and at the interface act as stress risers and contribute substantially crack initiation and propagation in the coating. Under increasing tensile load in the plastic region, the substrate material can no longer support the coating. This results in extended cracking and gradually spalling of the coat. When the local critical stress for crack propagation is reached, elongated cracks occur, which in turn initiates splitting separation between the adjacent zones in the coating. The shear deformation of the adjusted zones results in the total failures of the coating. Research limitations/implications - The tests can be extended to include the duplex treated workpieces such as the laser treatment of surface after HVOF sprayed coating. This enhances the bonding of the coating through thermal integration of the coating and the base substrate material. Practical implications - The results can be used to assess the HVOF sprayed coatings. Originality/value - This paper provides information on mechanical behavior of HVOF sprayed coating when subjected to the tensile force and offers practical help for the researchers and scientists working in the coating area.