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<p>This work investigates a 1.70&#xa0;wt% Ni-alloyed H13 hot-work die steel and systematically compares the effects of two heat-treatment routes—conventional quenching followed by triple tempering (Q+3T) and deep cryogenic treatment (DCT)-assisted triple tempering (DCT+3T)—on its microstructural evolution, mechanical properties, and 600&#xa0;°C sliding wear behavior. XRD–Rietveld refinement results reveal that both heat-treated conditions yield low retained austenite fractions; specifically, the γ-Fe content is reduced from 0.67% (Q+3T) to 0.36% (DCT+3T). Nevertheless, this marginal difference alone cannot fully explain the observed property variations between the two groups. In contrast, DCT exerts a far more prominent effect on carbide precipitation during tempering, resulting in remarkable refinement and homogeneous dispersion of M<sub>23</sub>C<sub>6</sub> carbides. The average equivalent circular diameter of the precipitates is reduced from 216.3 to 47.1&#xa0;μm, accompanied by a 183.6% increase in precipitate number density. Electron backscatter diffraction (EBSD) analysis indicates that the average geometrically necessary dislocation (GND) density shows negligible difference between the two conditions, whereas the DCT+3T specimen presents modified grain boundary characteristics and spatial distribution of defects. Mechanical property tests demonstrate that, despite a slight decrease in tensile strength from 2060 to 1929&#xa0;MPa, the impact energy increases from 10.1 to 30.5&#xa0;J, indicating a significantly optimized strength–toughness balance. High-temperature wear tests show that the wear rate of the DCT+3T specimen is reduced by approximately 31.5% compared with the Q+3T counterpart, with only a marginal decline in hardness from 52.4 to 51.2 HRC. This reveals that the enhanced wear resistance is mainly attributed to the transition of the dominant wear mechanism, from crack-controlled delamination wear to a more stable abrasion-dominated mode. Overall, DCT promotes the refinement and dispersion of precipitates, while synergistically regulating grain boundary characteristics and defect structures, thereby improving the damage tolerance and microstructural stability of the steel, and ultimately optimizing its comprehensive service performance.</p>

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Effect of deep cryogenic treatment on the microstructure and properties of Ni-alloyed H13 steel

  • 期刊论文

  • 发表日期：

    2026年4月9日

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  • Rongfu Xu,
  • Mingyang Bi,
  • Wendong Zhang,
  • Simon Yisheng Feng,
  • Yunshan Zhang

摘要

This work investigates a 1.70 wt% Ni-alloyed H13 hot-work die steel and systematically compares the effects of two heat-treatment routes—conventional quenching followed by triple tempering (Q+3T) and deep cryogenic treatment (DCT)-assisted triple tempering (DCT+3T)—on its microstructural evolution, mechanical properties, and 600 °C sliding wear behavior. XRD–Rietveld refinement results reveal that both heat-treated conditions yield low retained austenite fractions; specifically, the γ-Fe content is reduced from 0.67% (Q+3T) to 0.36% (DCT+3T). Nevertheless, this marginal difference alone cannot fully explain the observed property variations between the two groups. In contrast, DCT exerts a far more prominent effect on carbide precipitation during tempering, resulting in remarkable refinement and homogeneous dispersion of M23C6 carbides. The average equivalent circular diameter of the precipitates is reduced from 216.3 to 47.1 μm, accompanied by a 183.6% increase in precipitate number density. Electron backscatter diffraction (EBSD) analysis indicates that the average geometrically necessary dislocation (GND) density shows negligible difference between the two conditions, whereas the DCT+3T specimen presents modified grain boundary characteristics and spatial distribution of defects. Mechanical property tests demonstrate that, despite a slight decrease in tensile strength from 2060 to 1929 MPa, the impact energy increases from 10.1 to 30.5 J, indicating a significantly optimized strength–toughness balance. High-temperature wear tests show that the wear rate of the DCT+3T specimen is reduced by approximately 31.5% compared with the Q+3T counterpart, with only a marginal decline in hardness from 52.4 to 51.2 HRC. This reveals that the enhanced wear resistance is mainly attributed to the transition of the dominant wear mechanism, from crack-controlled delamination wear to a more stable abrasion-dominated mode. Overall, DCT promotes the refinement and dispersion of precipitates, while synergistically regulating grain boundary characteristics and defect structures, thereby improving the damage tolerance and microstructural stability of the steel, and ultimately optimizing its comprehensive service performance.