Stress corrosion cracking in an 18MN 5Cr retaining ring revealed by using NDE methods.Retaining Ring Stress Corrosion Cracking
Problem:Stress corrosion cracking (SCC) occurs on non-magnetic retaining rings—particularly those made from 18Mn5Cr alloy steel. The presence of high stresses (retaining rings usually are the most highly stressed component on a generator), and moisture or chlorides, will initiate cracking and pitting in this material. Laboratory tests have shown that when conditions are ideal for cracking, cracks can grow as fast as 0.001 inch per hour.