Temperature and stress during laser cladding of double-layer coatings

The time dependent temperature and strain–stress fields are numerically calculated for the laser cladding of a double-layer coating, and the example of stellite SF6 clad prepared on the X10Cr13 chromium steel is considered. The temperature dependent material properties and also the effects of the base preheating and time delay between cladding of the first and second layers are taken into account. For a coating on the non-preheated base the calculated strain stresses considerably exceed in both layers the limit of the SF6 tensile strength, whereas in the case with preheating to 600 °C the calculated values lie below that limit. A comparison of the numerical data for both cases leads to the conclusion that the micro-cracking susceptibility is smaller for the preheated base. This has been confirmed in the experiment that revealed cracks in the samples cladded on the non-preheated substrate, while crack-free coatings were produced with base preheated to a temperature of 600 °C. An increase of the cracking susceptibility with prolonged time delay between preparation cycles of the consecutive layers is evidenced, both in the experiment and modelling.