The effect of surface hardening by spark deposition of tungsten carbide on the life of hot-forging dies was assessed by Weibull analysis for several pinion punch dies. It was found that the coating was beneficial to die life if those factors which contributed to long die life governed the die behaviour whereas the coating was detrimental if those factors which contributed to short die life were governing the behaviour. The results showed that better temperature control of the billet heating arrangements produced significant improvements in the die life.
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