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%Na₂SO₄ and three salt mixture (3SM) Na₂SO₄-10%V₂O₅-10%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.

Highlights

• Alloy 718 was fabricated successfully by the direct metal laser sintering (DMLS) method.

• Cyclic high-temperature oxidation and corrosion of the alloy were studied at 800°C.

• The oxidised sample exhibits a lower weight gain with no damage.

• Due to chlorination and sulfidation, the corroded samples exhibited more oxidation and susceptible.

GRAPHICAL ABSTRACT

KEYWORDS:

• Alloy 718
• additive manufacturing
• hot corrosion
• oxidation
• microstructure

Disclosure statement

No potential conflict of interest was reported by the author(s).

Novel statement

In aerospace and other energy sectors, alloy 718 was subjected to corrosion attack in the presence of salt conditions at elevated temperatures. Microstructural differences between cast and additively manufactured parts play a significant role in corrosion performance. In this research work, the high-temperature corrosion performance of the direct metal laser sintered alloy 718 was investigated in the air, and molten salts (NaCl-90%Na₂SO₄ and Na₂SO₄-10%V₂O₅-10%NaCl) atmosphere at 800°C.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.