Oxidation of chromium carbide coated Q235 steel in wet and dry air at 750°C

Effect of heat treatment on microstructure and properties of powder immersion reaction assisted chromium carbide coatings prepared on Q235 steel

“…The parabolic oxidation kinetics (Figures 5 and 6) and the cross-sectional morphologies shown in Figure 7 indicate that the oxidation was controlled by oxygen diffusion through the formed chromia film, 18,30 and took place on the coating surface. Assuming that the oxidation products of chromium carbides were only Cr 2 O 3 and CO, related oxidation reactions can be expressed as The higher the parabolic rate constant for oxide formation, the faster the protective chromia film formation and the better the oxidation resistance.…”

“…During oxidation at 750 • C in the air, the oxidation weight gains of both the as-prepared and the further heat-treated samples could be well fitted by the parabolic equation. 18,30 𝑥 2 = 𝑘 p × 𝑡 (6) where x is the weight gain per unit surface area induced by oxide formation, k p is the parabolic oxidation rate constant and t is the time, respectively. However, the parabolic oxidation rate constant for the as-prepared and the further heat-treated coating was different.…”

“…However, due to different chrome carbide compositions, coatings prepared at different temperatures have different oxidation resistance and microhardness. 16,17 PIRAC chromium carbide coatings containing only Cr 23 C 6 have the best oxidation resistance, but the lowest hardness. 16,17 Therefore, for wear resistance applications in hightemperature oxidizing environments, PIRAC chromium carbide coatings containing multiple crystal forms are more effective.…”

“…16,17 PIRAC chromium carbide coatings containing only Cr 23 C 6 have the best oxidation resistance, but the lowest hardness. 16,17 Therefore, for wear resistance applications in hightemperature oxidizing environments, PIRAC chromium carbide coatings containing multiple crystal forms are more effective. However, during high-temperature oxidation, Cr 23 C 6 reacts with diffused carbon to form Cr 7 C 3 and Cr 3 C 2 .…”

“…However, during high-temperature oxidation, Cr 23 C 6 reacts with diffused carbon to form Cr 7 C 3 and Cr 3 C 2 . 17, 18 Verdi et al 19 reported that during the heat treatment at 800 • C, the elastic modulus and hardness of laser cladded Inconel 625-Cr 3 C 2 composite coating increased due to the formation of M 23 C 6 carbides enriched in Cr or Nb, and Laves phases. 19 Consequently, it is believed that further heat treatment can change the phase composition and properties of PIRAC chromium carbide coatings.…”