Research On Laser Cladding Repair Of Stainless Steel With Wire Feeding By Side

The laser cladding repair with wire feeding by side is a new repair technology. Basing on the principle of tracked or layered stack, the technology can repair scrapped or erosive parts by melting metal wire absolutely with the process of wire feeding automatically, needing no mould and cutting tool. In recent years, this technology has already become the research focus in the world. On the one hand, the application of this technology on common stainless steel has broad prospects in the market. On the other hand, due to laser cladding technology has little heat input, fast cooling rate, rapid solidification rate and other characteristics which traditional repair techniques do not have, it is of great significance for the research on rapid solidification microstructures and properties of cladding stainless steel.In this paper, the hot-rolled plates of 316 L stainless steel are used as substrate material. In order to repair surface and groove defects, the laser cladding with different wire feeding, including ER308 L, ER309 LSi and ER316 L stainless steel materials, is performed on the surface of substrate. Though the study of laser cladding processes, microstructures and properties of multi-track multi-layer cladding, the reasonable repaired scheme can be determined. The main contents and conclusions are as follows.(1) The laser cladding repair process with ER308 L stainless steel wire feeding by side was studied and optimized. When the laser energy density was 100 J/mm2, the wire fusion was 39.44 × 10-6 g/J, three combinations of process parameters under different laser power were obtained. The appropriate overlapping rate varied from 45 % to 53 %, ensuring that the value of multi-track single-layer cladding surface smoothness was 100 μm or less. Taking into account the practical application, the nice multi-track multi-layer cladding could be obtained when the layer spacing was 1 mm during the high-power laser cladding process.(2) In order to repair planar abrasion and shallow crack, by using ER308 L, ER309 LSi and ER316 L stainless steel wires, the surface laser cladding repair practice was carried out under the best combination of process parameters at high laser power. Through the comparative study of macroscopic quality, microstructure and mechanical properties of the cladding repaired layer, it was found that the cladding layer and the substrate into a good metallurgical bond, and the grain morphologies of the cladding layer were composed of mainly columnar dendrites, a few planar crystals, cellular dendrites and some equiaxed grains. Except the cladding layer of ER316 L wire was solidified in mixed FA and AF modes; the other two types of cladding layer were solidified in FA mode, and the average ferrite content of the former was about 4 %, while the latter two were about 10 %. The average microhardness of the cladding layer and the substrate were fairly and evenly distributed, and there were no softening zones in the heat-affected zone. The maximum values of tensile strength and elongation of the cladding layer were more than 90 % of the substrate. Ductile fracture was proved by the obvious dimple characteristics in the fracture surface. Finally, considering the cost and practical effects in the experiment and other factors, we believed that the ER308 L metal wire could be selected as the best repair wire of 316 L stainless steel substrate.(3) For solving serious defect, deep cracks and other problems, the trapezoidal slope shaped groove was designed. By selecting the ER308 L metal wire and appropriate laser cladding repair process parameters in the experiment, we successfully repaired the groove and achieved good results.