Hardened case-nitrided metal articles and methods of forming the same

A method of producing a hardened case-nitrided metal article, the method comprising:

• case-nitriding a metal article to produce a case-nitrided metal article, wherein the metal article is formed of a metal or a metal alloy, and wherein the case-nitriding comprises:
• heating a portion of the metal article to a nitriding temperature;
• and
• cooling the portion of the metal article from the nitriding temperature to a reduced temperature;
• hardening the case-nitrided metal article to produce the hardened case-nitrided metal article therefrom, wherein the hardening comprises:
• heating the case-nitrided metal article to an aging temperature;
• maintaining the case-nitrided metal article at the aging temperature for an aging time;
• and
• cooling the case-nitrided metal article from the aging temperature;
• and
• wherein the hardening is performed subsequent to the cooling the portion of the metal article from the nitriding temperature to the reduced temperature, and wherein the reduced temperature is lower than the aging temperature.

A method of hardening a case-nitrided metal article, the method comprising:

• heat-aging the case-nitrided metal article, wherein the heat-aging comprises:
• heating the case-nitrided metal article to an aging temperature;
• maintaining the case-nitrided metal article at the aging temperature for an aging time;
• and
• cooling the case-nitrided metal article from the aging temperature;
• wherein the case-nitrided metal article is formed of Ti-5553.