WELDING FOR PRODUCING RING BLANKS OF HEAT-RESISTANT NICKEL ALLOYS
Ring blanks made from difficult-to-weld heat-resistant dispersion-hardened nickel alloys are currently produced in a rolling form. Application of this technology is forced by a poor quality of welded joints. Choosing a technology for producing such rings in a welded form is a very urgent task. The main difficulties in welding these alloys are their low mechanical properties of the weld metal and their heat resistance. Electroslag welding with a combined electrode by simultaneous introduction into the slag pool nonconsumable and consumable electrodes was offered to manufacture nickel superalloy ring blanks. Welding is performed with an ANF-21 flux by the welding machine based on standardized units of electroslag devices and a TSHS-3000 source. To improve the quality of weld metal it was modified with refractory ultrafine particles of titanium carbonitride (0.04 %) using non-current-carrying flux cored nickel wire. The mechanical properties of modified weld metal were found to be improved significantly. They exceed specification requirements and the long-term strength surpasses the required one more than twice. Modifying process is shown to result in suppression of columnar nature of crystallization, in refinement of cast alloy crystal structure, in improvement of carbide phase morphology and topography, in improvement of γ''-phase which in its turn enhances mechanical properties of weld metal and its heat resistance. The results allow converting the technology of manufacturing of nickel superalloy blank rings from the rolling form into the welding one that provides a significant economic effect.