Reenactment sword replicas are not all the same. Particularly, the blade’s hardness determines how the sword will be used.
The majority of the swords sold by Res Bellica has blades of EN45 steel – i.e. spring steel -, a good type of steel that could reach a hardness of 55 HRC, if properly hardened.
Almost every replica of sword from Ancient History (for instance, the gladius) has a blade made of non-hardened EN45 steel. This feature means that, if a clash between swords shoudl happen, most probably it will cause the appearance of notches on the blade. However, they are still fit to be used during reenactment battles of this time period, since the main way to parry such swords is not by using another sword but the shield.
The reenactment combat of later periods, such as Late Antiquity and the Middle Ages, requires swords of a different kind, since it involves a lot more contact between the blades.
Some of the Res Bellica medieval swords have blades in hardened EN45 steel, with a 48 HRC hardness. However, to a swordplay which involves a lot of blades contact corresponds the frequent appearance of notches, particularly if the swords are used frequently and if put against swords with blades of harder steel.
For a completely battle-ready use, Res Bellica makes use of Hanwei blades. These blades are made of high carbon steel 5610, with a hardness between 50 and 52 HRC. These are blades of excellent quality, upon which notches will hardly appeare even after frequent use (note that notches will eventually show up if the blades will be put against even harder and better quality steel blades).