| Arc additive repair technology,as a low-cost metal repair technology with efficient forming and full use of materials,is not limited by the size of equipment forming chamber or vacuum chamber,and can repair large size parts in situ.After years of development,this technology has more and more obvious advantages in repair.Bainitic steel frog is usually repaired by bainitic steel,which has good matching of strength and toughness,but poor ductility and unstable plasticity.Based on this,this paper takes austenitic steel wire and Bainitic steel wire with excellent strong plastic matching as the research object,and uses plasma arc additive manufacturing system to study the process,structure and properties of the repair layer on the frog surface of bainitic steel.First studied the repair layer at the bottom of the deposition of metal material forming technology,the introduction of width to height ratio and dilution rate as an evaluation standard of single channel of weld,width to height ratio by using mathematical modeling in high precision meet the dilution rate and maximum minimum conditions to get the optimum parameters of the forming process of single channel,the follow-up to the optimal process of single channel to multi-channel lap strategy formulation,The optimum additive technology of single-layer multi-channel matrix repair layer was determined.Secondly,the microstructure and properties of the repair layer of high-flat austenitic steel and bainitic steel were analyzed and tested to master the microstructure of the repair composite joint and the internal microstructure of the repair layer.The results show that the frog substrate of austenitic steel-bainitic steel and the frog substrate of bainitic steel-bainitic steel are all integrated well,without shrinkage holes and other defects.The characteristics of the tissues from the frog substrate to the top of the repair layer of austenitic steel are:The grain coarsened from the bonding boundary to the bonding interface,columnar grain with disordered growth direction at the bottom,intracellular substructure at the top,columnar grain and intergranular equiaxed grain with the same growth direction at the middle,and interdendritic ferrite with disordered growth direction at the top.From the substrate to the top of bainite steel,the grain near the interface of the substrate becomes fine,and from the bottom to the top of the repair layer,the grain is first coarsed and then refined.Further,the performance test of the repair layer is designed.By contrast,the bainitic steel and austenitic steel repair layer have their respective advantages.The austenitic steel repair layer is more excellent in tensile strength,plasticity,fatigue and shear.Bainitic steel repair layer is more excellent in impact,wear and hardness.Finally,heat treatment optimization was carried out for bainitic steel repair layer.After heat treatment,the performance of bainitic steel repair layer can be improved to a certain extent.The maximum tensile strength and elongation after fracture are 974MPa and 35.6%,and the maximum hardness is 330.2HV0.5,and the minimum volume wear rate is 0.07mm3/（N*m）.Subsequently,the austenite was further optimized by heat treatment,and the strength change was not obvious.The other properties were improved to a certain extent.The elongation after fracture was up to 52.5%,the impact absorption energy was up to 52J,the hardness was up to 321.8 HV0.5,and the volume wear rate was up to 0.005mm3/（N*m）.The results show that the repair layer of austenitic steel has the best comprehensive performance when solution is dissolved at 1000℃for 4 hours. |
