Abstract This study presents a digital modernization and critical re-evaluation of the classical Grossmann–Asimow steel hard-enability model using an open-source 1D transient heat equation solver implemented in MATLAB. Beyond reproducing the historical 1940 master charts, the open code simulates complex profiles with temperature-dependent thermophysical properties ( ρ ( T ), C p ( T ), k ( T )) and non-linear experimental heat transfer coefficients (HTC exp ). Direct algorithmic superposition reveals that Grossmann’s historical H = 0,01 in (–1) curve corresponds precisely to a modern numerically solved H = 0,02 in (–1) trajectory, exposing a legacy mislabeling that has persisted in standards for decades. Parametric sensitivity analyses show that a constant thermal diffusivity ( α = 0,009 in 2 /s) introduces minimal error across 875 °C to 400 °C, validating Grossmann’s steady-state assumption. Furthermore, cumulative metrics ( t 0,5 , CR 400-875 ) provide superior dimensional stability over the single-point ASTM A255 CR 704 baseline. Comparisons with empirical water-quenching data confirm that traditional H -values represent linearized convective coefficients restricted strictly to the critical transformation window ( T 0 to T 0,5 ). The open-access code enables automated, PDE-constrained optimization of D I and H from experimental sectioning data.
Abstract Screen-assisted direct-current plasma nitriding (S-DCPN) was applied to ferritic stainless steel SUS430 to clarify the effects of screen material and open area ratio on nitrogen transfer and nitrided-layer formation. Ni screens with open area ratios of 49 % and 60 % were used to evaluate screen geometry, while SUS304, SPCC, and Ni screens at 60 % were compared to isolate material effects. Plasma nitriding was performed at 633–723 K for 5 h under a 75 vol.% N 2 and 25 vol.% H 2 atmosphere. Expanded ferrite (α N ) formed under all conditions. Compared with the 60 % Ni screen, the 49 % screen enhanced nitrogen transfer, resulting in thicker nitrided layers and earlier iron-nitride formation at elevated temperatures. In contrast, the 60 % screen formed persistent Ni-rich deposits that suppressed nitrogen transfer. Surface hardness increased with nitrogen uptake, whereas corrosion behavior depended on the distribution of iron nitrides and Ni-derived deposits. At the same open area ratio of 60 %, nitrogen transfer followed the order SUS304 > SPCC > Ni, demonstrating that screen chemistry strongly influences nitrogen transfer. These findings provide new insight into the nitrogen-transfer mechanism and practical guidelines for optimizing metallic screen design in industrial plasma nitriding.
Abstract Duplex stainless steels are widely employed in aggressive environments due to their unique combination of corrosion resistance and mechanical performance; however, their long-term reliability remains governed by complex interactions between alloy chemistry, manufacturing route, and secondary phase precipitation. This work provides a comprehensive comparative study of cast and wrought UNS S32205 and UNS S32750 DSSs, revealing how processing history and alloy design control microstructural evolution, precipitation mechanisms, and corrosion degradation. Thermal aging revealed a common precipitation sequence, with nitrides forming first, followed by χ and σ intermetallic phases. The refined microstructure of the wrought materials promoted faster precipitation kinetics compared with the cast counterparts. Despite their higher susceptibility to secondary phase formation, wrought super duplex 2507 exhibited enhanced corrosion stability (CPT ~76 °C) due to tungsten-induced modification of precipitation behavior and stabilization of the less detrimental χ phase.
Abstract Bainitic steels are widely used in bearing systems for demanding applications such as wind turbines, where surface integrity plays a decisive role in fatigue resistance and service life. Hard turning as a productive finishing process may thermally affect the workpiece surface layer, particularly once initial tool wear sets in. Fine finishing processes might be needed to correct the detrimental effect on functional properties in these cases. In this study, the influence of hard turning and diamond burnishing on surface roughness, residual stresses, and near-surface microstructural modifications is investigated. The results demonstrate that diamond burnishing reduces surface roughness by approximately 80 % in terms of R a and 78 % in terms of R z , while simultaneously introducing high compressive residual stresses averaging 1200 MPa to depths of up to 160 μm. Importantly, no evidence of white etching layers was detected on initially hard-turned specimens, indicating that the process primarily modifies the residual stress state and surface topography without inducing detrimental thermal effects. These findings highlight the potential of diamond burnishing to improve the functional performance and service life of highly loaded power transmission parts.
Abstract Roller shells of twin-roll-caster (TRC) are subjected to wear and tear due to their usage in harsh casting and forming conditions. Therefore, their durability is significantly shortened by the need to refinish the surface to reinstate suitable surface parameters for rolling and casting thin aluminium or other metal strips. To extend the lifetime of the rollers, a solution to repair the surface has to be found. Due to the constraints in the TRC process, most surface repair processes are not suitable, too complex (multistage heat treatment) or too expensive. Hence, high velocity oxygen fuel (HVOF) is a viable solution for applying a repair surface onto worn-down rollers, as this process is well-known and understood, already established in the industry, and potentially possible to integrate into the TRC process environment without disassembling the roller from the machine.
