Abstract

As with the conventional cladding process e.g. TIG, oxyactylene and plasma arc surface welding, where the interaction time is much longer and it results in superheat generation, which further Induces the post melting and also vigorous mixing of the pool, thus producing good interfacial bonding but more dilution, large H A Z and less hardness etc.. Whereas with the laser cladding process, the superheat generation could effectively be controlled over the length of the interaction time thus producing less dilution, small H A Z and higher hardness value etc.. In this process a molten pool of the pasted or blown powder with a complex three dimension al (3D) shape is formed on the substrate, by the laser beam interaction with powder material. This interaction time plays a crucial role for the desired successful cladding. In our present analysis we find that in a narrow range of power density and beam interaction time, the regime of laser cladding could further be classified (Fig.l) for evolution of coarse(C), fine(B) and very fine(A) dendrite microstructures. The experimental results which were performed with stellite #6 on Cr-Ni and mild steel using a 5KW CO2-laser in the stationary and oscillating beam mode, show that for longer interaction time there is a post melting due to the superheat of the molten pool and also the flow within the molten pool is vigorous, resulting In a better mixing, thus lowering the average temperature gradient of the interface which varies as the bulk temperature.

© 1996 IEEE