A study on the effect of tialn film coating on the wear behavior and morphological characteristics of nitrided H13 hot work tool steel

Metal molds used in plastic forming processes such as die casting, hot forging, extrusion, and injection molding are exposed to adverse effects including wear, thermal fatigue, oxidation, and corrosion. These problems cause material loss, increased energy consumption, and significant economic drawbacks. Hot-work tool steels containing chromium (Cr), molybdenum (Mo), and vanadium (V) are widely preferred due to their high strength, hardness, and toughness. To enhance the mechanical and tribological performance of these steels and to extend their service life, surface engineering methods such as nitriding, carburizing, carbonitriding, and physical vapor deposition (PVD)/chemical vapor deposition (CVD) coatings are extensively applied. In this study, experimental investigations were carried out on AISI H13 hot-work tool steel. After vacuum hardening, three different nitriding durations (6, 15, and 65 hours) were applied, and the samples were evaluated in terms of surface hardness, roughness, and microstructural features. Following the nitriding process, TiAlN coating was deposited using the physical vapor deposition method. Hardness tests revealed that the surface hardness reached approximately 2800 HV after TiAlN coating. In particular, the specimen subjected to 15 hours of nitriding exhibited a diffusion depth of about 270 µm while maintaining coating integrity, thereby achieving optimum performance. The results demonstrated that the GN2 specimen (15 hours nitriding) exhibited the most balanced performance with low surface degradation, high adhesion, homogeneous coating structure, and chemical stability. In contrast, prolonged nitriding (65 hours) negatively affected the morphological and chemical stability of the coating, as SEM and EDS analyses revealed cracks and elemental inhomogeneities. Wear tests indicated that the GN1 specimen achieved the lowest wear rate (0.019×10⁻³ mm³/N·m) and volume loss (0.0253 mm³), thus providing the highest tribological performance. However, considering coating homogeneity and long-term industrial applicability, GN2 proved to be the more balanced solution. In conclusion, the sequential application of vacuum hardening, 15 hours of nitriding, and TiAlN coating is recommended as the optimum process route for AISI H13 hot-work tool steel. This combination ensures an ideal balance between hardness, coating continuity, chemical stability, and tribological resistance, thereby contributing to the extension of service life in industrial applications of hot-work tool steels.