Just as CPM processing can allow higher alloy content for red hardness and wear resistance in high speed steels, it can also be used to produce high alloy cold work tool steels for increased wear resistance. The wear resistance of a tool steel is determined by the heat treated hardness and the amount and type of hard alloy carbides present in the microstructure. For example, at the same hardness, D2 exhibits better wear resistance than A2. This is primarily because D2 contains more chromium carbides than A2.
The hardest and therefore the most abrasion resistant carbides typically found in tool steels are the vanadium carbides. The cold work tool steels known for superior wear resistance typically contain significant amounts of vanadium with sufficient carbon to form high volumes of vanadium carbides. For example, in high speed steels, M4 (4% V) and T15 (5%V) are recognized as two of the most wear resistant high speed steels available for both cutting tool and cold work applications. In conventional tool steels, the highly wear resistant A7 and D7 are the high vanadium (4-5%V) versions of A2 and D2.
The most beneficial result of the CPM process has been the ability to make new high alloy grades. The CPM process provides a means of increasing vanadium levels beyond what is practical in conventional steelmaking. Taking advantage of this aspect of the CPM process, Crucible engineers developed CPM 10V for cold work applications. It was designed to optimize the vanadium content to provide superior wear resistance while maintaining the toughness and fabricating characteristics of the familiar tool steels D2 and M2. Introduced in 1978, CPM 10V quickly became recognized as the standard for demanding wear applications. It also served as the model for an entire series of Crucible CPM high vanadium grades - our “Killer V’s”- designed to bridge the gap between tool steels and carbide.
The “Killer-V’s” now include CPM 3V, 9V, 10V, 15V, as well as CPM M4HCHS with it’s 4% V. This family of high vanadium tool steels offers superior combinations of toughness and wear resistance as shown in the accompanying comparagraph. Our well-known CPM 10V has four times the wear resistance of D2, and CPM 15V is 50% more wear resistant than 10V. As a matter of fact, CPM 15V has the highest wear resistance of any tool steel, approaching that of carbide, but without the risk of brittleness. The latest addition is CPM 3V, which at HRC 58/60 provides impact toughness approaching that of S7, while still offering wear resistance higher than D2. Crucible continues to develop specific high vanadium CPM grades to meet a variety of wear/toughness requirements.