My experience with tungsten says no, but that may not be the norm in all circumstances. Many heavy duty contacts are made of tungsten/silver. They can be leached free of silver by prolonged boiling in nitric and water, but the remaining material tends to have a yellow color (on the surface) after the silver has been eliminated, and a somewhat yellow flocculent material forms as well. I get the idea that some of the tungsten is converted, but I have no idea to what.
I never experienced any black powders, but keep in mind, all of my processing was done with heat, usually at a boil, which saves a huge amount of time. If you processed without added heat, it's entirely possible that the tungsten may have broken down to fine powder, although that's not what I would expect. Sorry, I can't say with any degree of certainty.
I can comment that silver that was cemented form this process always yielded a deep blue color solution when washed with HCl and water. Truth is, that's the only time I'd wash my cement silver with HCl. It, otherwise, was just rinsed with water until it ran clear, then melted. It was obvious to me that something was being included in my recovered silver from contacts, thus the added wash cycle. Once melted and poured as an anode, the silver appeared to be free of the included material. I expect there was some cleansing by flux.
Harold