Order Matters: Sequential Mechanical Shot Peening/Laser Shock Peening Engineering for A100 Steel Tailors Hydrophobicity-residual Stress Trade-offs
Abstract
This study investigates the synergistic effects of mechanical shot peening (MSP) and laser shock peening (LSP) composite processes on the “wettability functionalization-mechanical strengthening” of A100 steel. By designing MSP-LSP (MSP followed by LSP) and LSP-MSP (LSP followed by MSP) sequences, the regulation mechanisms of hierarchical surface morphology, residual stress distribution, and wettability evolution were elucidated. Laser confocal microscopy revealed that MSP-LSP preserved periodic macro-waviness (1.25×1.25 mm2 pits) from LSP while enhancing micro-roughness (Sa=1.62±0.04 μm), achieving Cassie-Baxter state via multi-scale coupling. In contrast, LSP-MSP introduced higher residual compressive stress (-1271.93±10.92 MPa) due to secondary hardening but compromised macro-waviness integrity, resulting in lower roughness (Sa=1.50±0.08 μm) and contact angle (86.14° vs. 91.58° for MSP-LSP). Finite element simulations confirmed that process sequence governed deformation accumulation: LSP-MSP leveraged stress-gradient-driven non-uniform deformation to amplify residual stress (47.8% increase vs. single processes), while MSP-LSP optimized hierarchical structures for hydrophobicity through waviness-roughness synergy. X-ray diffraction analysis demonstrated that post-treatment dominated microstructural evolution, with LSP-MSP exhibiting higher dislocation density (FWHM=5.61° vs. 5.07° for MSP-LSP). The study establishes a process-sequence-dependent dual-performance optimization strategy: LSP-MSP prioritizes mechanical strengthening, whereas MSP-LSP enhances wettability regulation. These findings provide critical insights into tailoring composite surface engineering for aerospace materials requiring multifunctional integration.