Cyclic oxidation and hot corrosion performance of direct metal laser sintered and wrought alloy 718 at 800°C in air and molten salts containing Na₂SO₄, V₂O₅ and NaCl

Abstract

The main aim of this research work is to investigate the high-temperature cyclic corrosion performance of the wrought and direct metal laser sintered (DMLS) alloy 718 in the air and molten salts NaCl-90%Na 2 SO 4 and three salt mixture (3SM) Na 2 SO 4 -10%V 2 O 5 -10%NaCl atmosphere for 120 h at 800°C. The microstructure of the wrought and DMLS alloy illustrated the austenitic and dendrite structure. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to evaluate the structure and phase constitutions of the scale. Visual and microstructural evaluation of the alloy post-exposure indicates that corrosion is more prevalent in molten salt conditions, when compared to air, and Cl-species induced the active oxidation in molten salt. The oxide film development and damage mechanism were detailed and explained by a cross-sectional investigation. Significant spalling and sputtering were also noticed in the S3 salt mixture. This might be attributed to the rapid formation of oxide scales by vanadate, followed by dissolution of the oxide in molten sulphate and chloride. The results divulged that both AM-built and wrought alloy exhibited the similar corrosion properties and both the alloys were undergone severe degradation in MS condition.

Effect of Yttrium Additions on the High-Temperature Oxidation Behavior of GH4169 Ni-Based Superalloy

“…As GH4169 Ni-based superalloy is a key material for the preparation of aero-engine hot end components, the improvement of its oxidation performance is crucial, and how to give full play to the active element effect of rare earths is the focus of the current research. At present, there are few studies on the high-temperature oxidation properties of GH4169 alloy alloyed with rare earth, and the oxidation temperature is mainly below 950 • C [25][26][27][28]. Therefore, it is necessary to investigate the effect of yttrium on the oxidation behavior of GH4169 Ni-based superalloy at extreme temperature (1000 • C) and its oxidation mechanism.…”