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I've read that when using diamond wheels to grind ferrous metals, at high temperatures the carbon in the diamond becomes soluble in the iron thus damaging the diamond wheel.

Is it okay to use a diamond wheel to grind a non-ferrous alloy like Tantung? Is there some similar solubility issue? It's an alloy that has:

  • ~40% Cobalt
  • ~30% Chromium
  • ~15% Tungsten
  • ~4% Carbon
  • ~5% Nickel
  • ~5% Iron

So it does have a small amount of iron in it but I am not sure how big an issue this is. Nor do I know if there are solubility issues with the other elements.

I ask because I have a diamond wheel and a CBN wheel, and although CBN wheel will work, it is was more expensive and generally more useful than the diamond wheel. The diamond wheel is harder and wears less, and does not get anywhere near as much use so I want to use it when I can.

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I thought I heard of everything but not this, so I did a net search. Apparently this is a new less expensive way to put tungsten carbide into a cobalt matrix. One source describes it as cobalt matrix and a few describe as a casting. Apparently nickel and iron are low because some sources do not mention them. Regular tungsten carbide tools are WC powder mixed with cobalt powder, compacted very low porosity and sintered at about 2000 F. Some WC inserts are silver soldered into tools like drill bits and saw teeth. Chrome carbide may be added. The matrix is Co, occasionally with Ni, but the total is only several per-cent ( such as 12 % max). The Co and Ni do not dissolve any carbides during sintering. The Tantung is directly cast; the Co,Ni,W,Cr and C are melted together, that gives little control of the shape and size of the WC and CrC particles. The traditional WC is ground with diamond wheels however there is essentially no iron present. I doubt very much if diamond dissolves into iron during grinding. I suspect some other factor is causing the diamond wheel wear.

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  • $\begingroup$ My understanding is that there was a brief period after HSS but before the introduction of tungsten carbide where the non-ferrous high-cobalt/chromium alloys like Tantung and Stellite played the role that carbide did when HSS could not hold up. It is supposed to have higher hardness but more brittle than HSS just liek carbide, but not as much as carbide. Then carbide came along which was cheaper, and harder, with higher temperature, and again even more brittle. So they got displaced and did not spend much time in the spotlight as a cutting tool. $\endgroup$
    – DKNguyen
    Commented Feb 20, 2022 at 0:33
  • $\begingroup$ Tungsten carbide tooling is the cheaper of the two. Not necessarily because the material itself is cheaper per mass/volume (I don't know anything about that), but because you can get away with using a lot less of it. Tantung tooling blanks come in big chunks just like HSS blanks so it can sink heat and be sharpened so you pay for a lot of material. But a tiny carbide tip brazed onto a mild steel tool will survive due to its hardness and higher temperature resistance due to less sharpening and heatsinking required. I have heard of Tantung tips being brazed onto mild steel tools though. $\endgroup$
    – DKNguyen
    Commented Feb 20, 2022 at 0:33
  • $\begingroup$ Apparently a large Tantung casting can be made while WC is limited to compaction die size. I never encountered Stellite cutting tools but they have the elements found in the Tantung so it would be possible. HSS were in use before WW2 ; I have a 1956 Metals text that refers to HSS alloys developed in 1928. So I think they were available at similar time to Stellites. I worked in a plant that made WC inserts in 1957 and it was a well established industry as far as I could judge. $\endgroup$
    – blacksmith37
    Commented Feb 20, 2022 at 1:52

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