**4. Conclusions**

The impact of sub-zero treatment at the temperature of −75 ◦C and subsequent tempering on the microstructure, hardness, flexural strength and fracture toughness was investigated. The main obtained results can be summarized as follows:

• The population density of small globular carbides is increased by application of SZT at −75 ◦C, by the factor from the range 2.5 and seven.


**Author Contributions:** Funding acquisition, P.J.; Microstructural investigation, L.R.-T., P.J.; X-ray diffraction, M.K.; Dilatometry. J.K.; Flexural strength, fracture toughness testing, I.D.; Supervision, P.J.; Writing—original draft, review, editing, P.J., I.D.

**Funding:** The authors acknowledge that the paper is a result of experiments realized within the project VEGA 1/0264/17. In addition, this publication is the result of the project implementation "Centre for Development and Application of Advanced Diagnostic Methods in Processing of Metallic and Non-Metallic Materials – APRODIMET", ITMS: 26220120014, supported by the Research & Development Operational Programme funded by the ERDF.

**Conflicts of Interest:** The authors declare no conflict of interest.
