In this master thesis, the estimation of hardening depth of workpiece NV.22-DP.82 and all closely related topics with hardenability were discussed. The phase transformation mechanisms that are necessary in order to understand hardening were explained. Steel hardening procedure and the terminology that comes with it were defined. Hardenability as a term was clarified, as were the test methods for determining hardenability of the steel. Out of several methods for testing hardenability, the two most commonly used methods stood out: Grossmann's and Jominy's methods. For purposes of this thesis, Jominy's test method was explained into detail for the needs of the practical part of the thesis. In practical part of the thesis, theoretical knowledge of Jominy hardenability testing was applied. The entire standardized test procedure is presented, from making the test specimen itself to the final graphical representations of the hardness distribution of the given test specimen. Using the results from the previously conduced test, a Jominy curve was constructed which was then combined with the Crafts-Lamont diagrams for the purpose of obtaining the hardness distribution across the cross-section of the workpiece NV.22-DP.82. Two hardness curves for oil quenching with different agitation state were shown and based on these curves a conclusion was made about the effectiveness of the quenching medium regarding the hardness achieved in the workpiece.