Mechanical Model And Micro-morphology Evaluation Of SG Wheel Grinding Nickel-based Alloy GH4169 With Micro-lubrication

As an alloy with excellent comprehensive properties such as high temperature resistance,high strength and corrosion resistance,Nickel-based alloy is widely used in aerospace,naval vessels,chemical equipment and other fields.However,its advantages such as high hardness and high strength also bring difficulties to processing.How to reduce the grinding temperature and improve the surface quality of the parts has become a problem of the precision processing of nickel-based alloys.Despite the rapid development of special processing technology for nickel-based alloy materials in the past few decades,grinding still occupies a very important position in the processing and manufacturing of key nickel-based alloy parts.One of the main reasons for the development of modern grinding technology is the emergence of new abrasives.Traditional abrasives cannot meet the processing requirements of difficult-to-machine materials such as high hardness,high strength and strong wear resistance.Super-hard abrasives are suitable for processing nickel base alloy,but its trimming and manufacturing costs are relatively high.In 1981,Norton has prepared Seed-Gel ceramic corundum abrasive(SG)by adding seeds in the sol-gel process.Because of its good grinding performance and lower cost,it has become a cost-effective product between super-hard abrasives and traditional abrasives.However,the grinding mechanism and grinding wheel wear mechanism of the SG grinding wheel processing nickel-based alloy need to be further explored.In addition,fixed-shape SG abrasives represented by Norton's long columnar TG abrasives and 3M's triangular plate-shaped Cubitron^TMII abrasives are also widely used in the processing of difficult-to-machine metals.However,at present,the core technology of the SG abrasive production line with controllable particle shape is monopolized by foreign companies,and the import price is extremely expensive,which leads to the shortage of the abrasive in the domestic market.The use of high-quality grinding wheels can improve the grinding efficiency and the surface quality of the workpiece,as well as reduce the generation of grinding heat.Besides,how to enhance the heat dissipation in the grinding zone and explore a suitable cooling and lubrication method to reduce the nickel-based alloy grinding burn is also of great importance.In response to the dificuilt and crucial problems above,the paper carried out the research and development of the production line of controllable shape SG abrasive volume,the grinding performance and wear state of white corundum and SG grinding wheel were compared;and the position and angle distribution of abrasive particles on the surface of SG grinding wheel were theoretically analyzed.Based on the material removal mechanism and mechanical behavior,the SG wheel force model under different lubrication conditions was established and verified by experiments.Finally,the mechanism of nanofluid micro-lubrication in the process of SG wheel grinding of nickel-based alloys was analyzed.The thesis mainly includes the following research contents:(1)The application requirements,material mechanical properties and processing bottlenecks of nickel-based alloys were analyzed.The research and development routes of ceramic corundum abrasives at home and abroad were reviewed.The process flow and advantages of the sol-gel method for preparing ceramic corundum abrasives were analyzed.Besides,production technology of controllable shape SG abrasives at home and abroad were summarized.The advantages and technical bottlenecks of various cooling and lubrication methods were inquired.(2)The development bottleneck of my country's controllable shape SG abrasive mass production technology were analyzed.Based on the sol-gel method to prepare ceramic corundum abrasive production process,the production line transmission system,quantitative and precise coating system,multi-energy field intelligent drying and control system,particle collection and micro-mold cleaning system,mold release agent precision spraying and recycling system were sequentially designed.Furthermore,a complete production line for producing SG abrasive grains with controllable shape was constructed.(3)The wear mechanism of SG grinding wheel was analyzed and experimental research was carried out.The nickel-based alloy GH4169 was ground by white corundum and SG grinding wheel.The main wear mechanisms such as the adhesion,blockage and abrasive fragmentation of white corundum and SG grinding wheel was studied.The influence of grinding parameters on grinding force,workpiece surface quality and grinding specific energy was explored,and the multi-edge grinding mechanism caused by micro-fragmentation of SG abrasive particles was revealed.(4)The material removal mechanism of SG wheel/nickel-based alloy GH4169 was revealed.The contact state and area of a single abrasive particle and the workpiece were analyzed.A single pyramidal SG abrasive particle grinding force model based on the principle of material fracture and plastic accumulation was established.A pose model of the SG wheel surface abrasive grain angle and protrusion height conforming to the Gaussian distribution was established,and the cutting depth of the dynamic effective abrasive grain of the SG wheel was analyzed.Then the mathematical model of grinding force of SG wheel under dry,micro-lubrication and nano-fluid micro-lubrication conditions was established.(5)A numerical simulation model for the grinding force of the SG wheel under different lubrication conditions was established,and the results of the prediction of the grinding force were experimentally verified.Based on the theory of forced heat transfer in the grinding zone,the influence of grinding parameters on the grinding performance of SG wheels under three lubrication methods was explored.The cooling and lubrication mechanism of nanofluid micro-lubrication in the grinding process of SG wheel was revealed.