Method of Case Hardening a Group IV Metal

A method of producing a case hardened workpiece of a Group IV metal including: placing a workpiece of a Group IV metal in a vessel, creating a low pressure environment in the vessel in which the pressure, pvac, is less than or equal to 10 5 bar, providing oxygen to the vessel to create a reactive atmosphere in the vessel, the reactive atmosphere comprising oxygen at a partial pressure, pO2, in the range of 10 5 bar to 0.01 bar, heating the workpiece to a hardening temperature in the range of 650° C. to 800° C. in the reactive atmosphere or before the reactive atmosphere is created, maintaining the workpiece in the reactive atmosphere at the hardening temperature for a reactive period of at least 5 hours, cooling the workpiece from the hardening temperature to ambient temperature in the reactive atmosphere or in an inert atmosphere.