Fixed Abrasive-Based Study On Grinding Process Of SiC Mechanical Seal

Mechanical seals are indispensable key components in modern industrial equipment.As the sealing medium is often toxic and volatile,and the seals operate under complex working conditions of high temperature,high pressure,and high corrosion,the material of the sealing components and the quality of the sealing surface are of importance.Choosing the appropriate sealing material not only directly affects the sealing performance and the service life of the device,but also relates to environmental protection and safety production.Silicon carbide materials have several advantages,such as stable chemical properties,high thermal conductivity,low coefficient of thermal expansion,good wear resistance,and relatively low cost of artificial synthesis.Therefore,it has become the preferred material for mechanical seals.However,due to the high hardness of silicon carbide material（Mohs 9.5）and good mechanical properties,it is difficult to obtain a high-quality processing surface efficiently.At present,the processing technology for silicon carbide components is diverse,with a long production cycle and high processing costs,particularly for the contact surface of the sealing ring used in the mechanical sealing system.The silicon carbide component is ring-shaped,with a special structure and high requirements for the surface form accuracy of the workpiece.The traditional process requires experienced workers to perform precision lapping with grinding pastes of different particles several times,and the technical reliability is difficult to adapt to large-scale production.In this paper,considering the special structure of the silicon carbide sealing ring,the fixed abrasive technology is adopted to study its lapping process,and the following aspects are mainly carried out.First,based on the annular structural of silicon carbide sealing rings,a flexible fixture that can be adjusted is designed.The fixture is capable of processing circular workpieces with a diameter range of 4.5 cm to 7.5 cm and a thickness of 0.5 cm to 1.5 cm,enabling the clamping of multi-specification sealing rings with convenient positioning and reliable clamping.Second,the effect of different abrasive particle sizes on the lapping efficiency of the sealing ring is analyzed by using single-factor method.Under the premise of considering both efficiency and surface quality,diamond particles with size of W28 are selected as the free abrasive.The influence of process parameters on material removal rate（MRR）and surface roughness（Ra）is analyzed through orthogonal experiments.The results show that the factors affecting the MRR are in the order of lapping disc rotation speed,load,and slurry,while the factors affecting surface quality are in the order of slurry,rotation speed,and load.As a result,the maximum MRR is 0.0891μm/min,Ra is 0.0999μm,and PV is 0.697.Third,using W28 diamond fixed lapping pads,an orthogonal experiment is conducted under the same process conditions to analyze the effect of process parameters on the lapping efficiency of the sealing ring.The results show that the factors affecting the MRR are in the order of load,rotation speed,and slurry,while the factors affecting surface quality are in the order of rotation speed,slurry,and load.The result show maximum MRR in 0.546μm/min,Ra in 0.0461μm,and PV in 0.56.The use of fixed abrasives for processing turned out high efficiency and good surface quality.Later,in the process of lapping the sealing ring with fixed abrasives,an experiment is conducted to explore the effect of the slurry on the lapping efficiency by adding different additives.The results show that the addition of 15%alcohol and 1%silicon carbide mortar as an auxiliary agent,and0.5%Fe₃O₄ and 10%H₂O₂ as oxidants in the slurry can further improve the lapping efficiency.The average MRR and Ra are 1.737μm/min and51.8 nm,respectively.Finally,in order to explore the material removal mechanism of lapping the silicon carbide sealing ring with fixed abrasives,a material removal model is established.It analyzes the micro-cutting process of diamond abrasive grains,as well as the effect of the slurry on the self-sharpening of the fixed abrasive pad and the formation of the surface softening layer on the workpiece.