METALLOGRAPHIC ASPECTS OF CRACK GROWTH IN NIMONIC 80A UNDER SULPHIDISING CONDITIONS.

The corrosion of Nimonic 80A in kerosene with 0, 2. 5 and 5% sulfur is investigated. At 600 degree C, the crack growth studies and microscopic observations indicate that sulfur is not aggressive, especially at lower concentrations. At 700 degree C, experimental results indicate that sulfur has a marked effect on crack growth. The formation of the eutectic and further penetration are likely to be the main reasons for the deterioration of the alloy. The effect of sulfur on the degradation of the alloy is felt at longer exposure time. At both temperatures, scale spalling also contributes to deterioration of the alloy. At 700 degree C, catastropic destruction occurs due to sulfidation faciliting crack growth.