Laser surface coating of TiC on H13 die steel: Effects on corrosion and erosion behaviour

Coatings and surface are being extensively used to increase the service lif e of die casting dies by reducing molten metal corrosion and erosion of the die. Owing to their excellent corrosion and abrasion resistance, refractor y ceramic coatings are particularly suitable for coating die casting dies, and titanium carbide can provide significant resistance to molten aluminium corrosion and erosion. Technologies currently in use for applying such coa tings include physical vapour deposition, plasma spraying, and ion implanta tion. Laser surface engineering is a very attractive technique becuuse of i ts flexibility, non-equilibrium processing capabilities (involving high sol idification rates in the range 10(3)-10(8) K s(-1)), and ability to produce metastable phases nod increase the solid solubility limit beyond the equil ibrium phase diagram. Coatings thus produced are metallurgically bounded, w hich provides better substrate adhesion. The effects of the grain size of l aser coated TiC coatings and of laser surface treatment itself on corrosion and erosion behaviour of H13 die steel in molten Al casting alloy A390 wer e investigated in the present study. The corrosion rate is accelerated by t urbulence and by an increase in melt temperature. A significant improvement in corrosion resistance was achieved for H13 steel coated with TiC. Finer grain size and use of laser shock processing contribute to improved corrosi on and erosion resistance of steel in molten aluminium. Based on metallogra phic and energy dispersive spectrometry studies, the effectiveness of the c oatings along with possible reasons for their behaviour are discussed.