Investigation of the Properties of Fe-Zn and Al-Si Coated High-Strength Hot-Stamped Materials and Comparative Analysis of Delayed Cracking

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Tuğcular O., Akdikmen O., DEMİRAL Ö. F.

Gazi Mühendislik Bilimleri Dergisi, cilt.12, sa.1, ss.27-43, 2026 (TRDizin)

Özet

Automotive developments have spurred strong interest in lightweight and high-strength materials to enhance crash safety, reduce emissions, and improve fuel economy. Among these materials, boron– manganese steels processed by hot stamping are widely used in structural body components due to their excellent strength-to-cost ratio. To improve oxidation resistance during forming and to extend service life, protective Fe–Zn and Al–Si coatings are commonly applied. This study aims to comparatively investigate the delayed cracking resistance of Fe–Zn and Al–Si coated hot-stamped steels, considering the influence of different microstructures, residual stresses, and coating characteristics. Delayed cracking is a hydrogen- assisted failure mechanism that strongly depends on the material microstructure, applied stress state, and surface coating condition. In this work, an acid immersion test was combined with a mechanical delayed fracture (four-point bending) test to simulate both laboratory-controlled and realistic production-related conditions. Microstructural observations were conducted using optical microscopy and scanning electron microscopy to evaluate crack initiation and coating integrity. The obtained results provide useful insights into the relationship between coating type and delayed cracking behavior and serve as practical guidelines for material and coating selection in automotive body applications.