Abstract: To study the damage mechanism and corrosion resistance of 38CrMoAl steel materials under the combined effect of impact load and marine environment erosion, we subjected 38CrMoAl steel materials before and after nitriding to impact loading tests and corrosion performance tests. The studies found that the nitrided 38CrMoAl steel material has strong positive strain rate sensitivity at high strain rates. Under the impact load, cracks appeared on the nitriding layer on the surface of the test piece, accompanied by partial brittle peeling of the nitriding layer, with all crack lengths of 500-700 μm. The cracks only propagated in the nitriding layer without extending to the inside of the metal matrix. Electrochemical test results show that the nitriding treatment significantly improves the corrosion resistance of the material, with its self-corrosion potential shifting from -726.24 mV to -174.42 mV, compared with the non-nitrided specimen. However, due to the damage on the surface nitriding layer after the impact loading, part of the metal matrix is exposed, forming a potential difference with the undamaged surface, which in turn causes strong galvanic corrosion. The scanning Kelvin probe test showed that the anode-cathode potential difference and potential dispersion degree on the surface of nitriding parts are increased compared with the non-nitriding parts, and the nitriding parts are more prone to local corrosion. Impact loading changes the surface state of the nitrided layer, making the surface corrosion of the material more uneven. Finally, the salt spray test was carried out on the test piece, and the results were consistent with those of the electrochemical test. In the maintenance of the carrier-based aircraft, attention should be paid to the crack inspection of the nitrided layer of the impacted part, and corresponding anti-corrosion treatments should be done.

Key words: impact loads, 38CrMoAl, surface nitriding, Hopkinson bar, electrochemical tests