Cladding by Laser Heating Process

I think u must make preheating before cladding to decrease the cooling rate and so prevent cracks and deformation .

We are pre heating the shaft upto 200 deg centigrade.

We are doing cladding in two layers.After clading of 1st layer no problem.After 2nd layer cladding only the shaft got crack.We think there is a residual stress occured after 1st layer cladding. So now how to relive stress,with out putting in furnace. Because shaft diameter is 220 mm and length is 3000mm(too big to handle)

Deformation of shaft can probably be reduced (or even prevented) by ensuring uniform coating and cooling around the shaft. How fast do you turn the shaft during processing, for example?

Other than ensuring cleanliness and pre-etching the first cladding (I imagine you already do this) and limiting coating thickness (and I suspect you need the thickness you are depositing) cracking is without my area of expertise

I agree with elabd 110 who said your problem is thermal. Uneven heating and cooling during the cladding process will cause cracks and bending. Perhaps you can electrically heat the shaft by putting a current through it. Post cladding anealing or re-tempering may not be required if the shaft is heated well below the temperature which can change the base metal's hardness.

Heating the core may help, but the TCE of steel is far smaller than for any of the solid plastics, so (while worth a try) this may not be a solution. If you can use partially-pre-solidified plastics mixes, that may reduce the problem.