In laser remelting of thermally spayed ceramic coating, an increase in laser power from 400 W to 500 W shows a marginal increase in temperature. However, the tracks shows a signature of over melting. Here, Over-melting indicates increase in the track width.
I am wondering if the width of the melted track is higher for the 500 W exposure compared to the 400 W exposure? If that is the case more thermal mass is involved for the higher power case than the lower power case resulting in only a nominal increase in temperature? Doing a quick thermal transfer calculation will let you know if that is the case. Also take into consideration any radiation heat losses for each case
The width of the molten zone increases with the laser power at fixed scan speed. How did you measure the temperature? Can you measure the max temperature spot? The scanning speed of the laser beam can affect he maximum temperature difference in the affected zone with the laser powers. The faster scan, the less difference.
The thermal mass is almost same is each case. The material under consideration is plasma sprayed alumina coating (thickness range 250 -300 micron).
Srini Vasan
Xu Wang Time-temperature history of the remelted zone was monitored online using a infrared pyrometer. The laser beam (diameter= 5 mm) was Gaussian in nature so the maximum temperature spot is in the centre. Remelting was carried out using same scan speed but with different power. The difference in peak temperature for two different laser power was found to be marginal. Still, the melting width is more and poor surface quality was obtained at higher power
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