In situ Coating and Hot Corrosion Behavior of Cr 2 AlC MAX Phase

This study employs the spark plasma sintering technique to deposit the in situ Cr 2 AlC max phase on IN 738LC superalloy. The hot corrosion behavior of max phase coating in a salt mixture containing 40 V 2 O 5 + 60 wt.% Na 2 SO 4 at 900 °C in 5-h cycles was investigated. The XRD pattern of the samples demonstrated that the already formed corrosion products were Cr 2 O 3 , Al 2 O 3 , (Cr, Al) 2 O 3 complex, AlV 2 O 4 , NiAl 2 O 4 , Na 17 Al 5 O 16 , and Ni(Co 2 )O 4 . The coating sample exhibited satisfactory corrosion resistance for up to 30 h; however, after 40 h, microcracks appeared on the sample surface and then, after 50 h, the sample was completely degraded owing to spallation. The highest amounts of protective oxides, namely Cr 2 O 3 , Al 2 O 3 , (Cr, Al) 2 O 3 complex, were 48.1, 42, 78.8%, respectively. A significant increase in Al 2 O 3 phase within 50 h was accompanied by spallation and destruction of the samples.