Hot Corrosion of Some Heat Resisting Alloys by V₂O₅-Na₂SO₄-NaCl Mixtures

Abstract

The accelerated attack in an atmosphere contaminated with vanadate, sulphate, and halide which is often found in alloys for gas turbine or marine diesel has been examined by means of crucible test. Six different materials used for turbine blades or valves were tested in this investigation. Samples partly immersed in mixtures of vanadium pentoxide and sodium sulphate and/or sodium chloride were heated in air at temperatures of 700 and 800°C, and weight losses were determined after descaling. The results obtained are as follows:
(1) Mixtures of Na₂SO₄+0.5-70% NaCl and V₂O₅+10-40%(Na₂SO⁴+NaCl) were the most corrosive for these materials.
(2) At lower temperatures, all alloys were resistant to attack by Na₂SO₄/NaCl but above about 750°C, they were subject to severe effects. These reactions occurred only in the reducing environments.
(3) In the V₂O₅/Na₂SO₄ environment, there was a considerable attack for S 590, LCN 155, SUH 3, and SUH 31 at even 700°C.
(4) LCN 155 and YA2B were the most corrosion-resistant alloys in the Na2SO4/NaCl environment, but they were subject to some intergranular attack.
CRK 22 and YA2B have a comparatively good corrosion resistance in V₂O₅/Na₂SO₄mixtures.