ISO 3908:2009 specifies a gravimetric method for the determination of the mass fraction of insoluble (free) carbon in carbides and hardmetals.
This method is applicable to
- carbides of hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten and zirconium,
- mixtures of these carbides and binder metals, free of lubricant, and
- all grades of presintered or sintered hardmetals, produced from these carbides,
having a mass fraction of insoluble carbon between 0,02 % and 0,5 %.