Artisan Cutlery AR-RPM9 Knife Steel
Composition Analysis Graph, Equivalents And Overview

AR-RPM9(Artisan Cutlery) - AR-RPM9 is a proprietary alloy by Artisan Cutlery, introduced circa mid 2020. Initially, it was Promoted as a PM steel with rare earth elements, designed for high performance budget knives . However, later metallurgist tests disputed the claims, and in May 2024 Larrin published an excellent article on his blog AR-RPM9 Knife Steel is False Advertising. Long story short, AR-RPM9 is not a PM steel, but a Spray Form alloy. The only element that can be considered as a rare earth element in its composition is Cobalt. However, 0.30% of Cobalt can just as easily be counted as a trace element and it is unlikely that so little of Cobalt would have an noticeable effect on the steel performance and properties.
Shortly after, Artisial Cutlery admited a mistake, and in a separate Instagram post stated that earlier misinformation was a result of a gap in knowledge in their earlier marketing practices. In the end, not a happy story.
Actual steel producer is unknown at the moment, at least to me, if you know who makes it, please share the info. If I had to guess I'd say Ahonest Changjiang is a reasonable guess, since Artisan Cutlery used 8Cr13MoV stainless steel made by Ahonest Changjiang, but who knows. Composition remained a secret for a short while, until Artisan Cutlery posted it on their instagram page, in a short video, although still hard to find on the net.
At this time, it's clear that AR-RPM9 is a SF version of the well known Chinese GB standard 9Cr18MoV steel, somewhere in between AISI 440B and AISI 440C. The only element in AR-RPM9 not specified in the GB 9Cr18MoV steel spec is Cobalt mentioned above, however again, given the very low amount 0.30%, once could argue that trace amounts still allow AR-RPM9 to fall under GB 9Cr18MoV steel standard specification.
Technically AR-RPM9 is a high carbon steel with 0.90% C in it, and 18% Cr ensures good stain resistance. Interestingly also contains trace amounts of Vanadium(V) 0.1% and Cobalt 0.3%. Silicon range is a bit strange 0.20%-0.80% and along with the Nickel specified as < 0.40% those are the only ranges mentioned in their video, the rest of the alloying elements are shown with precision to 2nd decimal place and obviously that's an average number, no way anyone can produce anything budget resembling with that accuracy. In terms of edge holding, AR-RPM9 won't compete with AISI D2 steel used in other knives from the same maker, but it is deemed an upgrade over other budget alloys used by them - 8Cr13MoV stainless steel.
Tests published later show equal or sometimes worse performance compared to well heat treated GB 9Cr18MoV steel, let alone AISI D2 steel. Could've been a faulty batch, but in the end this isn't a really new steel.

Manufacturing Technology - SF

Country - China(CN)