Characteristics of Fe-, Ni- and Co-based Powder Coatings Fabricated by Laser Metal Deposition without Preheating the base Material

The objective of this work was to select the best material from Fe-, Ni- and Co-based alloy powder for coating, by Laser Metal Deposition (LMD) the filets of a hardened 42CrMoS4 extrusion screw without preheating process. Even though most of the articles recommended preheating the base material as a condition for a crack free coating, the time wasted in the process decrease the productivity and distortions can be also generated in the part. In this work, a comparison of the main characteristics of the coatings done on preheated and non-preheated base material has been made. The relationships between the relevant LMD parameters (feed rate, laser power, and powder feeding rate) and the main geometrical characteristics of a single clad (height, width, dilution, deposition rate, efficiency, etc.) were examined. In addition, different characteristics of overlapped clads in a preheated, non-preheated and a hardened base material have been also analyzed. All the study was made in the Ibarmia ZVH 45/1600 Add+Process hybrid machine with a high power Yb-Fiber laser (3 kW) and discrete coaxial LMD head. Coatings with thickness from 1.2 to 0.76 were created without cracks and other defects except in the case of Ni-based coating. The microstructural features of these coatings were studied using optical and scanning electron microscopy. The mechanical properties were determined using microhardness measurements and a pin on disk tribometer.