Mitigation and Prevention of Stress Corrosion Cracking Via Low Plasticity Burnishing

Stress corrosion cracking (SCC) is a costly and potentially catastrophic form of corrosion affecting industry. SCC requires tensile stress above a threshold, in addition to contribution from the environment, and the materials culpability to such damage. Classic approaches to combating SCC are: alloy control methods, use of coatings and other isolation methods, or use of beneficial compressive stresses. Low Plasticity Burnishing (LPB) is an established, low cost, closed loop controlled process performed using conventional CNC or robotic systems that imparts a deep, uniform, thermo-mechanically stable compressive residual stress distribution. This reduces the tensile stress in critical regions of components to levels below that required for SCC. The LPB process is engineered to meet the needs of specific applications. Accelerated testing is performed to confirm corrosion and fatigue modeling predictions for the imparted stress field. Real-time tool feedback confirms that the pre-determined compressive stress levels are achieved. Investigations were performed to evaluate the SCC resistance of 300M Steel in a marine environment and 304SS in an aggressive chloride environment. In both cases the compression imparted by the LPB process was successful in preventing SCC damage.