Variable diffusion carburizing method

A method of carburizing a powder metal part, the method comprising:

• carburizing, in a pre-forging carburizing step, a powder metal part that is less than fully dense to establish a pre-forging carburization profile, wherein a base carbon percentage of the powder metal part is 0.1 to 0.3 weight percent of the powder metal part prior to the pre-forging carburizing step and wherein a percent of carbon in a carburized region of the pre-forging carburization profile is 0.5 to 0.6 weight percent carbon after the pre-forging carburizing step;
• forging the powder metal part after the pre-forging carburizing step so that the powder metal part is increased in density and transforming the pre-forging carburization profile into an as-forged carburization profile;
• and
• carburizing, in a post-forging carburizing step, the powder metal part after the forging step thereby resulting in both further diffusion of carbon from the as-forged carburization profile into the powder metal part and further introduction of carbon into the powder metal part at a surface of the powder metal part.