Stellite 6 is the benchmark grade of the entire cobalt-base Stellite family and the most widely used wear-resistant hardfacing alloy in industrial service. Its nominal chemistry is cobalt balance with 27-32% chromium, 3-6% tungsten and 0.9-1.4% carbon, plus minor nickel, iron, silicon, manganese and molybdenum. That carbon and tungsten level sits at a deliberate middle point in the Stellite lineup: enough carbide volume to deliver excellent abrasion, galling and cavitation-erosion resistance, without pushing the alloy so far toward maximum hardness that toughness and weldability suffer, which is the trade-off made by higher-carbon grades like Stellite 1, 12 or 190.

Kennametal Stellite lists Stellite 6 at 36-45 HRC (380-490 HV) with a typical ultimate tensile strength of 850 MPa, a density of 8.44 g/cm3 and a melting range of 1250-1360degC (2282-2480degF). It retains useful hardness up to roughly 500degC (930degF), which combined with its low coefficient of friction and good resistance to mechanical and chemical degradation makes it the default choice for valve seats and gates, pump shafts and bearings, erosion shields, and rolling couples - it is frequently run self-mated against itself. It is registered under UNS R30006 (plus R30106, W73006 and W73036 depending on product form) and covered by AMS 5387, 5373, 5788 and 7239, as well as AWS A5.21 (ERCoCr-A rod, ERCCoCr-A wire) and AWS A5.13 (ECoCr-A electrode) welding consumable specifications.

Stellite 6 is regarded as the most machinable of the mainstream wear-resistant Stellite grades, which is one reason it is specified so widely for parts that need finish machining after casting or hardfacing - but it is still a genuinely difficult material by any conventional standard. The chromium and tungsten carbides dispersed through its cobalt-chromium matrix are extremely abrasive to cutting tool edges, and the alloy's thermal conductivity is poor compared to steel, so heat generated in the cut concentrates at the tool-chip interface instead of dissipating into the chip. That drives crater wear and edge rounding well before a carbide insert would show similar wear on an equivalent steel part.

Stellite 6 also work-hardens under mechanical and thermal load at the cutting edge, so light, hesitant, or interrupted cuts leave a hardened surface skin that is tougher to machine on the next pass. A constant, adequately heavy chip load - avoiding dwell and rubbing - is the single most effective way to manage this. The alloy also retains its strength and hardness at elevated temperature, so there is no useful thermal softening effect to exploit at higher cutting speeds the way there is with carbon or alloy steel. Positive, sharp, well-honed cutting edges on very hard PVD-coated carbide substrates, rigid workholding and tool clamping, and generous coolant delivery are the standard approach; Stellite 6 can be turned successfully with carbide tooling given these conditions, which is not true of the higher-carbon Stellite grades.