Material Removal Mechanism And Process Research Of Lapping Sapphire By Fixed Abrasive

Sapphire crystal, for its excellent mechanical and optical properties, has been gradually applied in many popular areas such as defense and civilian, which requires high processing efficiency and surface quality of sapphire. However, because sapphire has high hardness, brittleness and chemical stability properties, it is difficult to efficiently get high-quality of surface finish. Fixed abrasive technology has been widespread concerned for its high efficiency, process controllability, low cost and environmental protection, etc. In this thesis, the lapping technology was studied for sapphire using diamond fixed abrasive pad(FAP), including establishing a microscopic material removal model, and optimizing the process parameters, etc, which are presented as follows:(1) The concession of diamond abrasives on the FAP surface. The distribution model of abrasives is established, and the actual number of exposed diamond abrasives is analyzed and estimated. According to the micro protrusions matrix form of FAP substrate, the force and deformation of work-piece, abrasives, matrix ware explored in the process of lapping sapping. The results show that: after diamond abrasive force, with the plastic deformation of the work-piece cut deep, the concessions of wrap medium resin matrix is generated by the elastic deformation, and their distances are much larger than the depth of cutting.(2) The contact behavior between the FAP and sapphire. The micro convex distribution model of substrate surface is established, the relationship of sharing about lapping pressure between matrix and abrasives are analyzed, the influence of concessions on abrasive cutting depth is discussed, and the relationship of material removal rat, surface roughness and the maximum cutting depth is deduced, which is also verified through some experiments.(3) The material removal mechanism of lapping sapphire by fixed abrasives. The influence factors of material removal rate are broken down by item by item with the component processing method, the material removal model is established about Mechanical, chemical and its effect on the coupling, and the effects of various factors on the material removal rate by profiling through a series of experiments. The experiments show that the contribution of the diamond abrasive for material removal rate is about 95%, which is the dominant of material removal. In the process of removing the diamond abrasive grains, a purely mechanical action is about 63%, and the chemical mechanical coupling effect is about 32%.(4) The role of lapping fluid in the material removal. The chemical etching action of slurry for sapphire surface was analyzed by using nano-indentation and XPS depth profile. The chemical corrosion layer thickness of slurry for sapphire surface is estimated, the possible chemical reaction equation is qualitatively inferred, and the causes of softened surface layer are initially parsed.(5) The sub-surface damage of lapping sapphire by fixed abrasives. The sub-surface damage layer depth of sapphire work-piece is measured by using differential etching for different lapping ways, and its formation mechanism is explored. The specific methods of reducing the surface damage layer depth are put forward, which provide theory support for the lapping process optimization.(6) The process technology research of lapping sapphire by fixed abrasive. The structure parameters of FAP are improved by using single factor experiment method, which effectively reduced the grits of concession and fall off. The process parameters of lapping sapphire were optimized and analyzed by orthogonal experiments. The process time of lapping and polishing sapphire was greatly short by using optimizing parameter. It laid the foundation of its industrialization application.