Research On Powder Flow And Laser Cladding On Inclined Plane

With the development of marine economy,the role of marine engineering equipment in the development,utilization and protection of the ocean is becoming more and more important.However,the marine working environment is harsh,and if marine equipment is damaged and it cannot be repaired in time,it will cause great economic losses and environmental disasters.The laser additive technology has the advantages of small heat-affected zone and excellent repair quality.The application of underwater local dry laser additive technology to online repair and online surface strengthening of offshore equipment can significantly improve the safety and economy of offshore equipment.However,the local dry method requires a large air current to form a local stable dry area under water,and the transportation of powder under the high air current has an important impact on the quality of the repair area.In addition,it is inevitable to repair the inclined surface during the on-site repair of offshore equipment.Therefore,studying the transport behavior of powder under strong airflow and laser cladding on inclined surfaces has important theoretical significance and potential practical value.Based on the commonness of the above water and under water repair process rules of inclined plane in theory,the optimization of laser cladding process parameters of horizontal substrate and the simulation of its temperature field and flow field distribution are studied,and then the laser cladding process of inclined substrate and the evolution behavior of weld pool contour are studied.Due to the complex influence of large drainage air flow used in underwater partial dry laser cladding on the powder transport and aggregation behavior,this paper explores the influence of atmospheric flow and powder feeding process parameters on the powder transport behavior,which lays a foundation for further underwater laser cladding.The main research contents of this article are as follows:(1)The process of horizontal laser cladding GH3536 is explored.First,the horizontal orthogonal experiment is used to analyze the influence of various process parameters on the cladding layer: within the range of the designed process parameters,the laser power has a reverse relationship has a positive relationship with the melt height,and a positive relationship with the aspect ratio;the powder delivery mass flow rate has a positive relationship with the melt height and an inverse relationship with the aspect ratio.Then,through numerical simulation technology,the temperature field and flow field in the molten pool are obtained,and combined with the adjustment of process parameters,the mechanism of the influence of the material transport operation of the flow field in the molten pool on the contour of the molten pool is explained.(2)Based on the technology and mechanism of laser cladding on horizontal plane,the laser cladding process of tilted substrate and the evolution behavior of the cladding layer profile are studied.First,through controlled variable experiments,analyze the influence of substrate tilt angle,cladding direction,process parameters on the cladding layer: substrate tilt will significantly reduce the fusion height;the fusion height in the upslope direction will be slightly higher than that in the downhill direction;a moderate increase in laser power can moderately compensate for the decrease in melting height.Then,by adding factors such as gravity and laser energy caused by tilt to the simulation model,a comparative experiment of tilt cladding simulation is carried out,it is explained that gravity affects the material transport in the flow field of the molten pool during the cladding of the inclined surface,which affects the contour of the molten pool,and the laser energy drop caused by the tilt causes the temperature field of the molten pool to decrease and the melting height decreases.It is concluded that the front flow field in the molten pool flow field dominates the front slope angle,and the back flow field dominates the melting height.(3)The powder converging behavior of the laser cladding technology based on powder feeding under the impact of large air currents is studied.First,numerical simulation and experiment analysis are compared: the increase of powder feeding airflow can cause the slight decrease of powder concentration.The strong lateral airflow can significantly reduce the powder concentration and cause uneven powder concentration distribution.Then,numerical simulation technology is used to analyze the drainage performance and internal flow field under different drainage covers and different process parameters: when the drainage gas is close to the cladding head,the drainage effect is better,but the powder transportation behavior is affected;When the cladding head is far away,the drainage effect is poor,and the powder feeding airflow needs to be increased to optimize the drainage effect,but the powder transportation has a good performance.Finally,comprehensive drainage effect and stable powder delivery,select the appropriate drainage cover and corresponding process parameters.