Typically, between 0.5 and 1.0% (weight) of PM raw material is a wax-based lubricant that aids in the molding and ejection of a preform to reduce tool wear. During the early stages of sintering (the step after molding that fuses the powder particles together), the lubricant is burned away.
Here is an article from Metal Powder Review Magazine that discusses recent developments in PM lubricant technology.