| In order to meet the high surface quality requirements of tungsten alloy components,precision/ultra-precision machining of tungsten alloy becomes inevitably necessary.However,the surface quality achieved by mechanical processes such as cutting is below expectations due to the serious tool wear.Therefore,lapping and polishing are considered as subsequent processes to improve the surface quality of tungsten alloy.In this paper,the technology of precision lapping and polishing of tungsten alloy was studied,the main contents are as follows:Lapping experiment was carried out to study the variations of surface topography,surface roughness and material removal rate of tungsten alloy with abrasive particle size.The lapping process using 38 ?m and 18 ?m silicon carbide abrasives during rough lapping stage and 8 ?m diamond abrasives during fine lapping stage was determined.Polishing experiment was carried out to observe the variations of surface topography and surface roughness of tungsten alloy with polishing time.A micro-pit topography on tungsten alloy surface was revealed,and the influence mechanism of the micro-pit topography on surface quality of tungsten alloy was obtained.A material removal model of tungsten alloy polishing was established to reveal the formation mechanism,evolution mechanism and influencing factors of micro-pit topography under mechanical action.It was revealed that the hardness difference between two phases of tungsten alloy was the fundamental reason leading to micro-pit topography,and the polishing pressure had a great influence on this topography,the depth of micro-pits increased with the polishing pressure,and 30 k Pa was determined as the polishing pressure value of tungsten alloy.Contrast experiments were carried out to observe the differences of surface quality and material removal rate between acid and alkaline polishing.X-ray photoelectron spectroscopy analysis technology was used to study the change of surface element composition of tungsten alloy,the different material removal mechanism under chemical action of the acid and alkaline polishing was obtained,and the acid polishing slurry containing citric acid was selected to polish tungsten alloy.A combined process of lapping and polishing for tungsten alloy that can effectively inhibit the micro-pit topography was proposed,and a smooth tungsten alloy surface with surface roughness of Ra 7 nm was obtained,which proved the feasibility of lapping and polishing processes for tungsten alloy to achieve a high surface quality. |
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