A study on high temperature oxidation behavior of double glow plasma surface metallurgy Fe-Al-Cr alloyed layer on Q235 steel

摘要

The high-temperature oxidation behavior of Q235 steel coated with Fe-Al-Cr by using double glow plasma surface metallurgy method was studied in air at different temperatures of 500, 600 and 700 ℃, respectively. The Q235 and the 304 stainless steels were produced as the control samples. Electron microscopy, energy dispersive spectroscopy and X-ray diffractometry were carried out to investigate the surface morphologies, microstructures and phases of alloyed layer before and after oxidation. It showed that the structure of the Fe-Al-Cr alloyed layer was compact without any microstructure defects. This alloyed layer connected with the substrate metal by metallurgical bonding. At the temperatures of 500 and 600 ℃, the high temperature oxidation resistance of the Fe-Al-Cr alloyed layer was similar to that of the 304 steel, but 2-3 times higher than that of the Q235 steel. While at 700 ℃, the Fe-Al-Cr alloyed layer exhibited much better oxidation resistance than that of the 304 steel (2.5 times) and the Q235 steel (5.5 times). And this was because the special Al distribution (approximate Gaussian distribution) in the Fe-Al-Cr alloyed layer, which displayed the self-healing ability for the oxidation film on the surface of the Fe-Al-Cr alloyed layer in the high temperature oxidation conditions.