GTFiji--something to consider if you are in the U.S. Chrome plating is likely to take a big price increase in the near future due to OSHA's just released lower workplace limit for hexavalent chrome. So,make sure you have current quotes for plating when you factor in the cost savings of a change to plated 4340 from stainless.
If the Armaloy process is the typical electrolytic plating, using chromic acid, the answer would be yes. But, (and I may be wrong on this) I was thinking that Armaloy is some kind of chromizing process, not plating. If that is the case, you might not see a price increase.
Armoloy and other Thin Dense Chromium processes are a plating process without all the normal problems of electrolytic planting chrome.
The last time I was involved with TDC it was limited in deposited thickness so it will tend to reflect the properties of the base metal, the harder the base metal the better.
Rolling contact from a bearing might be a problem though the higher hardness you are specifying will help. A sliding sleeve bearing might be better.
I would definitely get in touch with Armoloy and discuss you design parameters with them.
I've had my best luck with the Texas Bunch, but that was some time ago. Their home office is in Illinois.
150 ksi UTS is easy for a decent heat of 4140 even in a 2" bar. Unfortunately some heats are on the low side of the hardenability elements (C, Mn, Mo, and Cr) so they don't harden worth a dam*. But if you have the time and a little hardenability knowledge, you can save some $$$.
