In the present work, the effect of carbide density on microstructure, hardness, wear rate, and fatigue limit of AISI H21 die steel has been studied. The specimens of H21 die steel have been employed hardening at 1195 °C, double tempering at 540 °C, cryotreatment at − 185 °C for 24 h, and soft tempering at 100 °C. The microstructure, hardness, wear rate, and fatigue limit of the conventionally treated and cryotreated specimens have been examined. The pin-on-disk machine has been used for the dry sliding wear test. The fatigue test has been carried out using constant amplitude rotating bending fatigue test machine which indicates enhanced fatigue limit for cryotreated specimens. The improvement in hardness, wear behavior, and fatigue limit of cryotreated specimens as a result of increased carbide density with reduced carbide size and retained austenite has been observed. The carbides Fe₆W₆C, Cr₂₃C₆ and Cr₇C₃ played an important role in increasing the hardness, wear behavior, and fatigue limit of the material. The Basquin’s equation was used for the analysis of the fatigue test. The minimum value of the fatigue strength exponent of Basquin’s equation shows the enhanced fatigue limit of cryotreated specimens.

中文翻译：

---

碳化物密度对H21模具钢疲劳极限的影响

在目前的工作中，研究了碳化物密度对AISI H21模具钢的组织，硬度，磨损率和疲劳极限的影响。H21模具钢的样品已在1195°C的温度下进行淬火，在540°C的温度下进行双回火，在-185°C的条件下进行低温处理24 h，并在100°C的温度下进行软化。已经检查了常规处理和冷冻处理的样品的微观结构，硬度，磨损率和疲劳极限。针盘式机器已用于干滑磨损测试。疲劳测试是使用恒定振幅旋转弯曲疲劳测试机进行的，该设备可提高冷冻处理试样的疲劳极限。硬度，磨损性能的改善，由于碳化物密度增加，碳化物尺寸减小和残留奥氏体，导致了冷冻处理样品的疲劳极限和疲劳极限。碳化铁₆ W ₆ C，Cr ₂₃ C ₆和Cr ₇ C ₃在增加材料的硬度，磨损性能和疲劳极限方面起着重要作用。Basquin方程用于疲劳测试分析。Basquin方程的疲劳强度指数的最小值表明，经过冷冻处理的试样的疲劳极限提高了。