Microstructure and mechanical properties of laser deposition repair BT20 alloy

Researches on the laser deposition repair of BT20 alloy forgings having hole damage were carried out, and the microstructure characteristic of laser deposition repair component was analyzed. There was a dense metallurgical bond between the repaired zone and the substrate. The Al, Zr, Mo, V elements were uniformly distributed without fluctuation and segregation from the matrix to the laser repaired zone. The repaired component experienced a continuous microstructural transition from duplex microstructure with equiaxed and lamellar / in the repaired substrate to the epitaxial coarser columnar with basket weave / through heat-affected zone. In the heat affected zone, the microstructure changed from bimodal structure to the basket weave structure gradually, and the repaired zone was characterized by a fine / lamellar microstructure with various random orientations, and the was about 0.4-0.5 m, which should be related to the rapid solidification and phase transformation during the process. It is found that unsuitable laser process parameters and large hole sloped angle can cause defects such as gas porosities and ill bonding. The results of repaired sample tensile test at room temperature show that the tensile strength approaches to the wrought BT20 alloy, while its toughness is a little higher.