High Temperature Corrosion of CoNiCrAlY–Si Alloys in the Liquid Phase of Na₂SO₄–NaCl

Abstract

As an extension of our previous work to develop a high corrosion resistant alloy for coating applications, a fundamental study of high temperature corrosion behavior of spark plasma sintered CoNiCrAlY alloys with varying Si content as 0, 10, 20 and 30% by mass has been performed. The high temperature corrosion tests were carried out in the liquid phase (melted salt) of Na₂SO₄–NaCl at elevated temperatures of 923 and 1073 K for up to 720 ks and at 1273 K for 72 ks. Our results demonstrate that the CoNiCrAlY alloy suffers from internal corrosion attack at these temperatures. On the other hand, the addition of 30 mass% Si leads to beneficial effects not only in the suppression of the formation of internal corrosion products, but also in reducing the growth of external oxide layer. In this paper, the high temperature corrosion behavior of CoNiCrAlY–Si alloys and the influences of Si addition on the corrosion resistance are intensely discussed.