A new type copper-based alloys for valve seat of automotive engines have been developed, which were directly deposited onto aluminium-alloyed cylinder head by a laser cladding technique.
These alloys have unique microstructures resulted from a rapid solidification of immiscible two liquid phases, in which coarse grains containing fine hard particles of borides and/or silicides (from liquid B) are homogenously dispersed in the heat-resistant copper-based solid solution (from liquid A).
The controlled irradiation of a high-frequency oscillated CO2 laser beam results in melting only the material powder for cladding on the aluminium-alloyed substrate and stirring the molten pool to form a homogeneous dispersion of liquid B in liquid A, and then rapidly solidified to freeze the dispersion by the heat conductivity the aluminium-alloyed substrate.
The deposited alloys provided considerable abrasive- as well as adhesive-wear resistances at a wide temperature range owing to the unique microstructures consisting of hard particles, heat-resistant matrices and/or lubricating phase.
