Toolox® 44 has been subjected to extensive fatigue testing by SWERIM, a Swedish metal research institute. The purpose of the tests was to compare different samples of Toolox® – in delivery condition, plasma nitrided and induction hardened – to a 42CrMo4 steel. The high core hardness of Toolox® 44 means that this steel doesn’t need as deep induction hardening as 42CrMo4. Surface hardening results in higher compressive stresses in the surface, which is always beneficial to the fatigue strength.
The fatigue tests were carried out with notched round bar samples in a rotary bending machine with a 2 million revolutions target. The tests showed that Toolox® 44 has a high fatigue strength in as-delivered condition. Through surface hardening with plasma nitriding and induction hardening the fatigue strength is increased even further, as shown in the table Fatigue limit. SWERIM concludes that Toolox® 44 is suitable for fatigue loaded components. Surface hardening is recommended for the most demanding applications.