Why don't other suppliers also use larger carbides in their nickel-base alloys?
Rottstegge: Perhaps because the entire manufacturing process required to achieve the desired surface quality and the required diameter tolerances is particularly difficult and costly when large carbides are used. We decided to use large carbides because of their utility value and we then optimized the manufacturing process accordingly. Here, we have the major advantage that we were able to match the surface treatment of the wear protection layer (honing) to the exact requirements needed since we develop and manufacture the tools ourselves. This is also a core process at Reifenhäuser Reiloy!
So far, we have talked about nickel-based alloys. What about hardness as a comparative parameter of iron-based alloys?
Rottstegge: It's a similar story here. First, we also asked ourselves why our iron-based alloys achieve verifiably longer barrel service life at the same hardness. And then, in precise microstructure analyses, EDX analyses of the chemical composition, and, above all, in microhardness measurements, we worked out that it is due to the almost ceramic layer that other alloys do not possess.
Could you explain this in a little more detail?
Rottstegge: We are talking here about ceramic phases in combination with boron and carbon – mainly chromium-based – which are produced by the melt during the casting process. The objective of our concept is to generate a protective shield out of ceramic phases. These phases are still bonded in a metal matrix but occupy a large volume. In other words, the layer has a high hardness but is still sufficiently elastic. The entire process is geared to this. To produce the ceramic phases exactly the way we require, the composition, process temperatures, and process times must be precisely maintained. The process window is very narrow and must be exactly controlled. But we always get it right since we use the special Reiloy centrifugal casting process that we have continuously adapted and optimized over the years and we execute the entire process on specially developed machines