This paper aims to compare the behaviour of cobalt and iron base hardfacing alloys on hot forging dies under temper, shock and wear. Tempering resistance, shocking behaviour and wear resistance were investigated using a tubular furnace, press and pin on disc tribometer respectively. The results showed that the thermal stability of commercial iron base hardfacing alloy (named RMD248) is good below 550uC but poor in the case of higher temperature, whereas the cobalt base hardfacing alloy presents superior tempering resistance. The cobalt base hardfacing alloy possesses excellent shock hardening properties at all the experimental temperatures, but RMD248 does not, especially at high temperature (600uC). Compared with the hardfacing layer produced by RMD248, the cobalt base hardfacing layer produces high wear resistance at 600uC and high temperature oxidation resistance at 600uC for 100 h.

The properties of three cobalt based hardfacing deposits containing 0?37, 0?56 and 0?82 wt-% of carbon were studied. The results showed that hardness is enhanced with the increase in carbon contents in the case of as deposited condition and tempering treatment. The increasing rate in hardness increases with the increase in tempering temperature and time but declines with the increase in carbon contents in the hardfacing metal. In addition, the wear loss decreases with the increase in carbon contents at room temperature (RT) and 600uC. In comparison, there is a significant increase in the amount of wear of the metals at 600uC to that at RT. Oxidation tests at 600uC for 100 h showed a slight variation in weight loss of cobalt based metals with different carbon contents. It was also found that the carbon content reduces the crack resistance of cobalt based hardfacing deposits.

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