Need Help!- Machining 1" wide x 2-1/4" deep slot

[midguard]

I need some help or advice on machining a 1.00" wide slot x 2-1/4" deep.
The part is 2.50" diameter with a 1.500 diameter turn down that has a 3/8" key. We are clamping the 1.50 diameter and locating off of the 3/8" key. The part sticks 4.75" above the vise jaws. We had an inserted 3 flute cutting running at .17 DOC, running about 550 rpm and 2.3 IPM. Finished the slot to size with 5/8" 3 flute. It was taking a hour for two parts. That's way to long. Then after talking to tooling tech at MSC they said to use a 5/8" 4 flute Accupro with 2.25 LOC at 733 RPM 8.2 IPM and .562 DOC. The $190.00 tool did not get through the first cut before exploding. So here I am looking for any recommendation for a cutter and speeds and feeds. More details. We only have ER32 collet holders or end mill holders. The machine is a Fadal 3016L 15HP 7500 RPM spindle.
Lots of vibration on this part. Thinking about trying a rougher or semi rougher at 1/4 depth. Think tool wear would be excessive though.

[Smrtman5]

Material?

[midguard]

Sorry, good thinking. 1018CR.

[HSM_SCG]

Hi, I would use a 10mm 4 flute solid carbide end mill (£15 each) with a 20mm depth running on no more than a 10% wrap around @ 5000rpm with a 0.2mm step over at 2 m/min. cheap cutters fast feed big depth of cut. Sorry about the metric figures lol

[Ed from NY]

I would try a 1/2" 4-flute carbide cutter, RPMs to at least 3000 and start with a light DOC's and 20 IPM. If it works Increase the DOC. If you increase the RPM i would keep the inches per tooth between 0.001-0.002". It it chatters at first try backing off the DOC.

Edit:If you are spiraling down you may wat to use a lower IPM depending on the machine. Something like 12 IPM may work. If you are plunging less.

If you blow up another tool at least it will be a cheap one