Synergistic effect of temperature and CO2 on corrosion behavior and mechanism of laser cladding Ni/WC composite coating

• Laser-clad Ni-WC coating is prepared by laser cladding technology. • Austenitic dendrites, WC particles, and fishbone-like precipitation are observed. • The Lowest R p and highest i corr are found at the CO 2 partial pressure of 1.5 MPa. • MCO 3 on the WC particles further promotes the corrosion around WC particles. Laser cladding technology was employed to fabricate a Ni/WC composite on 4145H steel. The synergistic effect of temperature and CO 2 on corrosion mechanism of laser cladding Ni/WC composite coating was studied. Microstructural analysis reveals that the laser cladding Ni/WC composite coating predominantly consists of austenitic dendrites ( γ -Ni), WC particles, and fishbone-like precipitates, including W 2 C, MoC, and CrC. Electrochemical results indicate that a decrement in polarization resistance ( R p ) and an increment in corrosion current density ( i corr ) occur as increasing temperature without CO 2 . In addition, i corr without CO 2 is approximately 7 times lower than that under CO 2 of 1.5 MPa at 80°C. Corrosion mechanism illustrates that galvanic cell corrosion between WC particles and Inconel 625 causes pitting corrosion, which is further enhanced by the deposited layer, including CaCO 3 and MgCO 3 on WC particles as both temperature and pressure escalate.