As has been mentioned, Tungsten Carbide melts at an incredibly high temperature. Someone isn’t likely to be able to melt and cast Tungsten Carbide without a dedicated facility for such a purpose.
First, a source of tungsten carbide. Old machine cutting tools. Cutter inserts. Manufacturers collect the broken inserts for recycling as the scrap cost is rather high. Perhaps your characters could find an abandoned scrap supply or raid a manufacturing center.
Second, they would have to crush the used inserts. A big hammer and lots of pounding. Smaller than pea gravel. Between the size of peppercorns and sand. It’ll take a lot of pounding, but the stuff is pretty brittle, so if you hit it hard enough, you will break it up.
Finally, you would want a binder. Commercially, they use nickel (that is how the inserts themselves are made, with a very fine powder (almost flour consistency) mixed with nickel powder and pressed into shape and sintered around 2000F. Plenty hot, but a forced-air charcoal fire will do it.
For fiction, they could take coins, which are an alloy of nickel and copper, grind them up for a powder, mix it with the pulverized machining inserts and press it into a mold of the required shape. Although very delicate, the pressed forms would hold together well enough to go to a air-blast charcoal furnace to heat them high enough to get the nickel-copper powder to fuze with the tungsten carbide powder. Dimensional control wouldn’t be the best, but you could grind to size once cooled.
Now, for non-fiction, this might not work, you would need the crushed tungsten carbide to be the consistency of sand or finer and the nickel powder would need to be much purer than ground-up coins, but I’d guess that the number of people who would be able to tell you what effect of the high copper content would be is very small, perhaps less than 10,000 people in the US, while the number of people who would agree with the basic steps would number in the hundreds of thousands, if not millions.
That is, it would probably work for a Sci-Fi novel. Certainly more believable than a universal translator. If scientific accuracy is of utmost importance, have your characters find a store of tungsten carbide and nickel powder from a manufacturer of the cutting inserts, and then they just have to mix them, press them in a mold, and sinter the blanks.