Abstract

A systems-level understanding of microstructural degradation and stress corrosion cracking (SCC) is essential for ensuring the integrity and reliability of API 5L X65 compressor piping used in gas transmission and compression facilities. This study presents a comprehensive framework that integrates metallurgical, mechanical, environmental, and operational factors to explain the initiation and propagation of SCC in X65 pipeline steel. The framework synthesizes insights from materials science, corrosion engineering, and fracture mechanics to describe how microstructural features such as grain size distribution, phase balance, dislocation density, and inclusion morphology interact with applied stress and corrosive environments. Particular emphasis is placed on the role of residual stresses from welding and fabrication, cyclic operational loading, and pressure fluctuations typical of compressor station service. The study explains how these stresses, when combined with exposure to near-neutral or alkaline environments containing carbonates, bicarbonates, and moisture, promote localized anodic dissolution and hydrogen-assisted cracking mechanisms. The proposed systems-level model illustrates degradation as an evolving process in which microstructural damage accumulates through corrosion-fatigue interactions, strain localization, and crack coalescence. It further highlights the influence of operational parameters such as temperature gradients, flow-induced vibration, and gas composition on accelerating damage evolution. By adopting a holistic perspective, the framework moves beyond isolated failure explanations and demonstrates how coupled physical processes govern SCC susceptibility and crack growth behavior in API 5L X65 compressor piping. The study underscores the importance of integrating microstructural characterization, stress analysis, and environmental monitoring into integrity management programs. Practical implications include improved risk-based inspection planning, enhanced material selection and welding practices, and the development of mitigation strategies such as stress relief, coating optimization, and environmental control. Ultimately, the proposed framework provides a structured basis for predicting degradation trends, improving failure prevention, and extending the service life of compressor piping systems. The paper contributes to advancing systems-oriented integrity assessment approaches that support safer, more resilient, and more sustainable operation of critical energy infrastructure in high-demand industrial environments worldwide. It also establishes a foundation for future empirical validation, multiscale modeling, and digital twin development to support proactive maintenance decision-making under increasingly stringent safety, reliability, and regulatory expectations across global networks.