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<p>The performance of hot-forging tools is governed by temperature-driven thermomechanical degradation and associated wear mechanisms of surface-engineered layers operating under severe contact loading. This study investigates the high-temperature degradation and wear mechanisms of Orvar 2&#xa0;m hot-work tool steel modified by two industrially relevant but architecturally distinct surface engineering routes: diffusion nitriding and deposition of a nanocomposite CrN-based PVD coating system incorporating a TiC-containing interlayer, without the formation of a conventional diffusion-hardened subsurface zone. Laboratory-scale ball-on-disc sliding tests were conducted at 250–500&#xa0;°C under contact conditions representative of hot die forging to identify temperature-driven transitions in dominant wear and degradation mechanisms and to assess the thermomechanical stability of the surface-modified layers. The laboratory results were subsequently confronted with observations from industrial forging exposure in order to evaluate the predictive capability of ball-on-disc testing for different surface engineering strategies. The diffusion-nitrided variant exhibited moderate improvements under laboratory conditions; however, under industrial forging conditions its performance was limited by cracking, fragmentation, and localized loss of the nitrided layer, indicating insufficient thermomechanical stability and a temperature-driven overestimation of durability by laboratory-scale testing. In contrast, the CrN/TiC-based coating system, characterized by the absence of a diffusion-based subsurface gradient, demonstrated a fundamentally different degradation response, maintaining structural integrity and stable surface behavior across the investigated temperature range. The low and stable friction response of the coated system was associated with its high thermal stability and resistance to temperature-activated oxidation-assisted degradation. The results demonstrate that ball-on-disc testing reliably captures temperature-driven wear and degradation mechanisms but does not necessarily predict service durability of diffusion-based surface treatments. The findings provide insight into the relationship between surface engineering architecture, temperature-driven thermomechanical stability, and wear mechanisms of hot-work tool steels under realistic forging conditions.</p>

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Temperature-driven thermomechanical degradation and wear mechanisms of surface-engineered Orvar 2 m tool steel under laboratory and forging conditions

  • 期刊论文

  • 发表日期：

    2026年3月24日

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  • Marek Hawryluk,
  • Łukasz Dudkiewicz,
  • Magdalena Jabłońska,
  • Jerzy Smolik

摘要

The performance of hot-forging tools is governed by temperature-driven thermomechanical degradation and associated wear mechanisms of surface-engineered layers operating under severe contact loading. This study investigates the high-temperature degradation and wear mechanisms of Orvar 2 m hot-work tool steel modified by two industrially relevant but architecturally distinct surface engineering routes: diffusion nitriding and deposition of a nanocomposite CrN-based PVD coating system incorporating a TiC-containing interlayer, without the formation of a conventional diffusion-hardened subsurface zone. Laboratory-scale ball-on-disc sliding tests were conducted at 250–500 °C under contact conditions representative of hot die forging to identify temperature-driven transitions in dominant wear and degradation mechanisms and to assess the thermomechanical stability of the surface-modified layers. The laboratory results were subsequently confronted with observations from industrial forging exposure in order to evaluate the predictive capability of ball-on-disc testing for different surface engineering strategies. The diffusion-nitrided variant exhibited moderate improvements under laboratory conditions; however, under industrial forging conditions its performance was limited by cracking, fragmentation, and localized loss of the nitrided layer, indicating insufficient thermomechanical stability and a temperature-driven overestimation of durability by laboratory-scale testing. In contrast, the CrN/TiC-based coating system, characterized by the absence of a diffusion-based subsurface gradient, demonstrated a fundamentally different degradation response, maintaining structural integrity and stable surface behavior across the investigated temperature range. The low and stable friction response of the coated system was associated with its high thermal stability and resistance to temperature-activated oxidation-assisted degradation. The results demonstrate that ball-on-disc testing reliably captures temperature-driven wear and degradation mechanisms but does not necessarily predict service durability of diffusion-based surface treatments. The findings provide insight into the relationship between surface engineering architecture, temperature-driven thermomechanical stability, and wear mechanisms of hot-work tool steels under realistic forging conditions.