HIGH TEMPERATURE ATTACK OF NIMONIC 80 A BY VANADIUM.

The objective of the study is to investigate the metallographic aspects of crack growth behavior of Nimonic 80 A when subjected to tensile stress in the presence of vanadium corrodent. Crack growth is affected by the vanadium level in kerosene fuel and specimen temperature. At up to 20 ppm vanadium at 600 degree C, crack growth is accelerated. Beyond this level, the effect of vanadium is less. At 700 degree C a similar trend is observed, but the attack is very severe up to 20 ppm V. 40 ppm V has less effect than 20 ppm vanadium. The scales formed during hot corrosion contain many oxides. The scales are spongy. Eutectic liquid is formed during the experiment which has a low melting point. As the vanadium content increases, some of the vanadium may participate in forming vanadates, so increasing vanadium beyond a certain level will not monotonically be aggressive. This critical level is around 20 ppm V.