Study Of Healing Effect For Metal Crack By Pulse Current

Remanufacturing engineering is the performance recovery process of remanufacturing workblanks that have residual life by the usage of advanced technology, and it has a positive role in promote the strategy of sustainable development. Crack damage makes the reliability of material decreased quickly. Cracking is one of the most frequent failure modes in metallic structures. The research about repair of metal cracks is an important part of remanufacturing engineering.In this paper, the crack healing effect in metal by electropulsing treatment and the combined treatment of electropulsing and laser have been studied in detail. In order to detect the microstructure change after healing treatment, the metallographic microscope, electron back scattering diffraction and electronic probe method were adopted. And for the mechanical property change, the tensile and fatigue property test, fracture scanning, nanoindentation and Vickers hardness test were conducted. The healing mechanisms for each method were also analyzed in detail.In the study process, the through crack damage specimens in SUS304 stainless steel were made by "drill-compress" method. The different processing parameters of pulse current, multiple electropulsing treatment and gradient-energy electropulsing treatment were conducted for specimens to study the healing effect. The study found that the detour effect existed when pulse current flow through crack in metal, high temperature and local compressive stress were formed under the Joule heating effect. The crack healing effect could be realized at proper parameters. Test results showed that columnar crystals were formed during the process of rapid melting and solidification in healing areas, and fine recrystallization zone were formed around healing areas at the same time. The tensile strength and elongation were both promoted after healing treatment.The deep crack damage specimens in TC4 titanium alloy were also made by "three-point bending-pressure maintaining" method. The combined treatment of electropulsing and laser was conducted for specimens to study the healing effect. Electropulsing treatment were applied firstly to achieve crack healing partially, the deep crack was turned into shallow crack after the process. Then the shallow crack was healed by the method of laser remelting. The crack was healed obviously after combined treatment, the healing areas formed by electropulsing treatment and the''remelting zone-heat effect zone-matrix" structure could be distinguished, both the tensile and fatigue property were promoted obviously.