Welcome to the forum
What kind of steel at what hardness?
PCD is mainly used on abrasive silicon-aluminum alloys and cannot be used on ferrous materials.
You will most likely want to use good coated carbide endmills with mist or compressed air.
Also spindle speed,tool run out, and tool holder balance will be important limiting factors.
Your best bet would be contacting your tool supplier for feeds/speeds and advice.