Laser surface cladding was applied on a TC4 Ti alloy to improve its surface properties. Mixed TiC and Ti powders with a TiC-to-Ti mass ratio of 1：3 were put onto the TC4 Ti alloy and subsequently treated by laser bea...Laser surface cladding was applied on a TC4 Ti alloy to improve its surface properties. Mixed TiC and Ti powders with a TiC-to-Ti mass ratio of 1：3 were put onto the TC4 Ti alloy and subsequently treated by laser beam. The microstructure and composition modifications in the surfaee layer were carefully investigated by using SEM, EDX and XRD. Due to melting, liquid state mixing followed by rapid solidification and cooling, a layer with graded microstructures and compositions formed. The TiC powders were completely dissolved into the melted layer during melting and segregated as fine dendrites when solidified. The inter-dendritic areas were filled with fine a＇ phase lamellae enrich in A1. Mainly due to the reduced TiC volume fraction with increasing depth, the hardness decreases with increasing depth in the laser clad layer with a maximum value of HV1400, about 4.5 times of the initial one.展开更多
Laser cladding with coaxial powder feeding is one of the new ponent to improve performance of its surface. In the process, processes applied to produce well bonding coating on the com- the clad material is transported...Laser cladding with coaxial powder feeding is one of the new ponent to improve performance of its surface. In the process, processes applied to produce well bonding coating on the com- the clad material is transported by the carrying gas through the coaxial nozzle, generating gas-powder flow. The powder feeding process in the coaxial laser cladding has important influence on the clad qualities. A 3D numerical model was developed to study the powder stream structure of a coaxial feeding nozzle. The predicted powder stream structure was well agreed with the experimental one. The validated model was used to explore the collision behavior of particles in the coaxial nozzle, as well as powder concentration distribution. It was found that the par- ticle diameter and restitution coefficient greatly affect the velocity vector at outlet of nozzle due to the collisions, as well as the powder stream convergence characteristics below the nozzle. The results indicated a practical approach to optimize the powder stream for the coaxial laser cladding.展开更多
基金Project(J51402) supported by the Leading Academic Discipline Project of Shanghai Education Commission,ChinaProject(gjd08004) supported by the Foundation for Excellent Youth Scholar of China+2 种基金 Project(08QA14035) supported by the Shanghai Science and Technology Development Foundation, China Project(0852nm01400) supported by the Special Foundation of Shanghai Education Commission for Nano-Materials Research, China Project(08520513400) supported by Crucial Project of the Shanghai Science and Technology Commission,China
文摘Laser surface cladding was applied on a TC4 Ti alloy to improve its surface properties. Mixed TiC and Ti powders with a TiC-to-Ti mass ratio of 1：3 were put onto the TC4 Ti alloy and subsequently treated by laser beam. The microstructure and composition modifications in the surfaee layer were carefully investigated by using SEM, EDX and XRD. Due to melting, liquid state mixing followed by rapid solidification and cooling, a layer with graded microstructures and compositions formed. The TiC powders were completely dissolved into the melted layer during melting and segregated as fine dendrites when solidified. The inter-dendritic areas were filled with fine a＇ phase lamellae enrich in A1. Mainly due to the reduced TiC volume fraction with increasing depth, the hardness decreases with increasing depth in the laser clad layer with a maximum value of HV1400, about 4.5 times of the initial one.
基金supported by the National Natural Science Foundation of China(Grant Nos.11272316 and 11272317)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Laser cladding with coaxial powder feeding is one of the new ponent to improve performance of its surface. In the process, processes applied to produce well bonding coating on the com- the clad material is transported by the carrying gas through the coaxial nozzle, generating gas-powder flow. The powder feeding process in the coaxial laser cladding has important influence on the clad qualities. A 3D numerical model was developed to study the powder stream structure of a coaxial feeding nozzle. The predicted powder stream structure was well agreed with the experimental one. The validated model was used to explore the collision behavior of particles in the coaxial nozzle, as well as powder concentration distribution. It was found that the par- ticle diameter and restitution coefficient greatly affect the velocity vector at outlet of nozzle due to the collisions, as well as the powder stream convergence characteristics below the nozzle. The results indicated a practical approach to optimize the powder stream for the coaxial laser cladding.
