Adhesion and microstructure of laser cladded coatings

The application of a new cladding technique requires in addition to wear resistant alloy a good coating adhesion on the base material. Laser cladding is as far as his character is concerned a welding process, but the cooling times are short and the base material dilution is very low. So far, the related coating adhesion problem did not receive the necessary attention. The investigation is based on an adhesion tensile test with reference to DIN 50160. A fitting pin was fixated in a body of same material and the surface of both was cladded with a single track. Afterwards the pin was pulled out of the body and the necessary power was measured. Power related to the pin section was used to compare various combinations of base and adding metals. The tests have shown that the specimen of X8 CrNiTi 18.10 (austenitic steel) or C 45 (ferritic/perlitic steel) as base metal welded with the adding alloys Stellite 6, Stellite 157, Deloro 22 and Deloro 40 could bear loads from 300 up to 750 MPa. Part ially, those unexpected high values caused an exceeding of the breaking strength of the pins. For the cases, where the pins broke in the coating, two results can be distinguished: Firstly, the measured fracture loads of ferritic/perlitic steel specimen were higher than the austenitic steel specimen and, secondly, the fracture load decreased with growing welding speed.