Tubes of Mantle’s Flowable Metal Paste
By Steve Connor, Ph.D., Mantle Co-Founder and Chief Science Officer
People often ask us why we call our first Flowable Metal Paste material “P2X” instead of P20 (whereas our second Flowable Metal Paste is just called H13). We do this because we’ve formulated our P2X material to provide the performance of P20 steel, but we used somewhat different chemistry to achieve these properties. Our alloy is formulated differently because we need to be able to 3D print and sinter it, and these processes for P20 aren’t going to produce the same hardness as cast blocks that are slowly cooled. Also, since sintering inherently produces some amount of porosity (our materials are 97% dense), we wanted a material that is tougher and stronger than standard P20 to offset this porosity. We could achieve this in two ways: through formulation chemistry or via a post-print hardening or quenching process, which would add extra time and cost to our customers. Obviously, we took the chemistry approach. Because the metallurgy differs slightly between conventional P20 and our material, we call it P2X. As you may have read in our P2X Material Performance Study, it machines and EDMs like conventional P20 and has a hardness of 32-34 HRC, which is all that matters for most toolmakers.
We started with a P20 formulation because one great use case for Mantle is prototype and bridge tooling, which P20 is commonly used for. Prehardened P20 typically has a Rockwell hardness of 32, and even its high-hard (HH) variant has a Rockwell hardness of 35. This means that most tool shops have machining centers capable of handling P20 versus a much harder material like H13, which not every shop can work with. We also wanted to start with a material familiar and proven in the tooling industry. You could say that we opted for a material that offered high accessibility and familiarity, which makes comparisons to conventional tool steels more meaningful.
Once we developed P2X, toolmakers asked us for a harder material. While we could have selected a precipitation-hardened alloy like high-strength maraging steel or a 17-4PH martensitic stainless steel, we ruled those materials out for several reasons. First, maraging steel is as hard as H13 but not as abrasion-resistant. Also, since it is precipitation hardened via intermetallic compounds, we would have needed to use cobalt. In powder form, cobalt is highly regulated and toxic—not something we wanted to work with. While 17-4 PH can be hardened at relatively low temperatures, it’s extremely sensitive to carbon and easily degraded if it gets too hot. We opted to go with a material like H13, which is tough but still relatively ductile and can be sinter-hardened instead. In contrast to the P20/P2X naming difference, we called our H13 product simply “H13” since its formulation is the same as conventional H13.
What are we going to do next? We have some ideas, and we’ve been doing some work, but I’ll leave that discussion to another post at another time.
Advantages of Mantle’s P2X and H13 Materials
- P2X offers the performance of P20, a very common tool steel nearly all shops can handle, in a formulation that can be printed and sintered and still hit P20’s target Rockwell hardness level.
- H13 offers greater hardness plus ductility in a formulation that can be sinter hardened rather than precipitation hardened, allowing us to avoid working with materials like cobalt.
Steve Connor, Ph.D., is the Co-Founder of Mantle and its Chief Science Officer. He has 15 years of experience in materials development at both top academic laboratories and in industry. He holds a doctorate in Chemistry from Stanford University and a B.S. degree in Chemistry from the University of California-Berkeley.
