Deposition and post heat treatment of Ni-Al/Ni-20Cr on AISI 4140 using twin wire arc spray method

Boiler generates heat from combustion and transfers to change the water to steam phase. The boiler consists of several components, one of them is superheater tube. High temperature corrosion often attacks the superheater tube material causes material failure. This study aims to deposit Ni-Al and Ni-20Cr on AISI 4140 using twin wire arc spray method as barrier coating. Gas pressure during process was varied of 3 bar, 4 bar, 5 bar, and 6 bar followed by annealing to reduce porosity of the coating product. Characterization to investigate the morphology of the coating surface using SEM shows that the increase pressure causes small surface particles that affects to decrease porosity. Porosity at pressure 3 bar is 15.43% while at pressure 6 bar is 10,35%. In addition, the annealing process has contribution to reduce the porosity till 3% for pressure 6 bar. The hardness of the coating is also influenced by the pressure and the annealing process.