Heat Affected Zone in Surfacing Chromium Ledeburitic Steel

Repair welding is not used enough in the industry 1 . One of the reasons for this lies in the insufficient and unrealiable knowledge in many segments of this area. A very important part is having appropriate knowledge of metallurgical processes in heating of the base material 2-4 . Unsuitable heating deteriorates the microstructure as it reduces toughness and fracture behaviour of the weld 5 . We observed the changes in the HAZ of surfacing welds produced by the TIG and micro-plasma process. By surfacing we were repairing the cutting tools 6 made of the cold work chromium ledeburitic steel. Tool steels are very demanding for surfacing 7-11 as they tend to crack. That is why they need to be preheated and are cooled off slowly after the welding process. For a long time manual arc welding was the most important process for repair welding of tools but now it is becoming less important because the coated electrodes are difficult to weld with in low current intensity which is very important in surfacing the smaller tools or cutting edges. It can be reached with a TIG process which was used for repairing the tools. Micro-plasma welding which is similar to TIG process is also often used. The difference is in the fact that the arc of the plasma is more narrow and the energy more concentrated 12-15 . Laser surfacing has also become very efficient and important for repairing tools.