The application of cryogenic treatments is gradually increasing in tool steels. In this sense, these heat treatments can modify the mechanical properties of high chromium alloy steels. However, the influence of the cooling parameter (during quenching) is often neglected. This investigation aims at evaluating the effects of cooling parameter and cryogenic treatment on microstructure and fracture toughness of AISI D2 tool steel. The cooling parameter (λ) was defined as the cooling time from 800 to 500 °C divided by 100. During quenching, different cooling parameters (λ1 = 2.8 and λ2 = 1.8) were employed, and the samples were tempered three times or, besides, cryogenically treated by a single tempering. Later, the samples were evaluated through phase analyses and their proportions, sizes, and distribution of carbides by optical and scanning electronic microscopy, hardness measurements, x-ray diffraction, and fracture toughness tests. For the λ2 cooling parameter followed by cryogenic treatment, the results presented an increase of 51% over the initial condition of secondary carbides. However, the higher hardness values were found in the λ1 cooling parameter followed by cryogenic treatment. In the fracture toughness evaluation, a reduction of 8% in K_IC was observed for samples with cryogenic cycles compared to the samples without it.

低温处理在工具钢中的应用正在逐渐增加。从这个意义上讲，这些热处理可以改变高铬合金钢的机械性能。但是，冷却参数（淬火期间）的影响常常被忽略。这项研究旨在评估冷却参数和深冷处理对AISI D2工具钢的组织和断裂韧性的影响。冷却参数（λ）定义为800至500°C的冷却时间除以100。淬火期间，不同的冷却参数（λ1 = 2.8和λ2 = 1.8），将样品回火3次，或通过单次回火进行低温处理。后来，通过相分析以及通过光学和扫描电子显微镜，硬度测量，X射线衍射和断裂韧性测试对碳化物的比例，大小和分布进行了评估。对于随后进行低温处理的λ2冷却参数，结果表明，与次级碳化物的初始条件相比，其增加了51％。然而，在被发现的更高的硬度值λ 1的冷却参数随后深冷处理。在断裂韧性评估中，K _IC降低了8％ 与没有低温循环的样品相比，具有低温循环的样品观察到的是。