Type-II hot corrosion investigation of the DS200 +Hf superalloy at the γ/γ' scale

Type-II hot corrosion behavior was investigated on the Ni-based superalloys DS200+Hf, precoated with Na 2 SO 4 , in a flowing O 2 –SO 2 –SO 3 atmosphere. Corrosion products were characterized as an outer oxide layer rich in Ni and Co, and a complex inner layer including S and O. Investigations at the nanoscale of the propagation front revealed the formation of a partially crystallized WS 2 network, ordered along the c-axis with the γ/γ’ microstructure. Statistical measurement of the affected depths showed that the corrosion rate followed a parabolic law as a function of time from 550 °C to 700 °C. • Directionally solidified DS200+Hf exhibits from 550°C low temperature hot corrosion. • The corrosion rate followed a parabolic law as a function of time from 550 °C to 700 °C. • A solid-state mechanism explains the corrosion behavior of the DS200+Hf alloy. • A partially crystallized WS 2 network develops from the γ/γ’ microstructure at propagation front. • WS 2 network contributes to rapid outward diffusion of nickel in corrosion products.