Performance of Al₂O₃ hydrogen isotopes permeation barriers deposited on AISI 316L by Pulsed Laser Deposition

Hydrogen isotope permeation through structural alloys represents a critical challenge for tritium management in fusion systems. In this work, the performance of a 1 μm thick Al₂O₃ coating deposited by Pulsed Laser Deposition (PLD) on AISI 316L stainless steel is quantitatively assessed under fusion-relevant conditions. Permeation experiments were conducted using deuterium between 400°C and 500°C and at upstream partial pressures of 100–500 Pa. A matched pristine–coated dataset enables a direct evaluation of the permeation reduction factor (PRF), yielding values between 8.6 × 10² and 2.5 × 10³, corresponding to a systematic reduction of approximately three orders of magnitude. A resistance-in-series formulation shows that the coating resistance dominates transport in all investigated conditions (Rc ≫ Rs), confirming that the film acts as a functional barrier rather than a marginal surface modification. Factorial statistical analysis of ln(PRF) indicates that pressure exerts a stronger degrading effect on barrier performance than temperature within the explored domain, while a complementary multi-level model confirms the robustness of this trend. Response surface models for permeation flux and PRF provide continuous engineering maps over temperature–pressure space. In parallel, Monte Carlo inference of the pressure exponent in ln(J)–ln(p) space reveals a transition from near bulk-controlled transport in pristine AISI 316L to surface/film-controlled behaviour in coated samples, indicating that the PLD coating fundamentally alters the rate-controlling mechanism. The proposed framework provides a transferable, uncertainty-aware methodology for the quantitative assessment of permeation barriers and supports the potential of PLD-deposited Al₂O₃ as an effective tritium permeation barrier under fusion-relevant conditions.