Hybrid Cryogenic–Thermal Cycling Strategy for Enhanced Residual Stress Relief in Additively Manufactured Stainless Steel Components

Residual stress management remains a significant challenge in metal additive manufacturing, particularly in Laser Powder Bed Fusion (LPBF) processes, where steep thermal gradients induce internal stresses that compromise dimensional accuracy, fatigue life, and structural integrity. Conventional stress-relief methods are often inadequate for high-performance alloys like stainless steels.

This study proposes a novel hybrid post-processing route that combines deep cryogenic treatment (DCT) with low-temperature thermal cycling (LTTC) to improve residual stress relaxation in LPBF-fabricated stainless steel components. DCT facilitates the transformation of retained austenite into martensite, refining the microstructure, while LTTC aids in dislocation movement and stress redistribution through microplastic deformation.

LPBF specimens were subjected to three treatments: (i) no treatment, (ii) DCT alone (–196 °C for 12 hours), and (iii) DCT followed by LTTC (three cycles between 150–300 °C). Characterization through microhardness testing, optical and scanning electron microscopy, and X-ray diffraction-based residual strain mapping revealed that the hybrid-treated samples exhibited up to 35% reduction in tensile residual stress, enhanced microstructural uniformity, and improved surface hardness without dimensional distortion.

The results validate this hybrid method as a cost-effective, scalable, and scientifically sound approach for residual stress mitigation in AM parts, with broad applicability in aerospace, biomedical, and precision tooling sectors.