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Статья. Опубликована в журнале "LLE Review". – 2005. – Vol. 105 – P. 51-62.
Название на русском языке: Изучения на базе метода магнитореологического полирования прецизионного микрошлифования поверхности карбидов вольфрама.Аннотация к статье на английском языке:We have studied the response of five nonmagnetic WC composites to deterministic microgrinding. Grinding experiments showed that grinding-induced surface roughness decreased with decreasing diamond abrasive size. Microgrinding with a rough tool (40-nm grit size) involved fracture, leading to a p–v surface roughness in the range of 3.2 to 5.8 nm (150- to 700-nm rms). Microgrinding with medium and fine tools (10- to 20-nm and 2- to 4-nm grit size, respectively) was controlled by plastic flow. The medium tool led to p–v surface roughness values in the range of 0.5 to 3.8 nm (27- to 200-nm rms), whereas the fine tool resulted in surface p–v values in the range of 53 to 86 nm (7- to 13-nm rms). The true grinding-induced surface roughness was concealed by the deformed layer on the ground surface. We have demonstrated that a MRF spot can be placed on ground surfaces of tungsten carbide and that the spot can be used to evaluate the depth of the surface deformed layer. For the rough and medium tools, the deformed layer is in the range 1.5- to 2.7-nm. The surface roughness of MRF spot at the deepest point of penetration can be used as a guide for establishing the optimal amount of material to be removed by MRF. Optimal MRF removal indeed removes the deformed surface layer caused by grinding. Excessive MRF removal may lead to preferential polishing and removal of the binder phase, also known as grain decoration. By utilizing both surface-roughness measurements and SEM imaging at the spot ddp, we were able to estimate the depth of the deformed layer. Thus, we showed that the depth of the deformed layer can be estimated in two ways. An optical profilometer-based measurement of the p–v surface microroughness of the ground surface provides an upper bound to the deformed layer thickness. This is a desirable estimate given the noncontact nature of this metrology technique. On the other hand, the MRF spot can also be used to reveal the depth of the deformed layer while reducing the surface roughness.
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A Magnetorheological-Polishing-Based Approach for Studying Precision Microground Surfaces A Magnetorheological-Polishing-Based Approach for Studying Precision Microground Surfaces of Tungsten Carbides Introduction Tungsten carbide (WC) hard metals exhibit a unique combination of hardness and toughness, which makes them desirable engineering materials for wear-resistance applications such as cutting and milling tools.1 The mixing of the hard and brittle WC particles with the more soft and ductile binder produces a composite with optimal mechanical properties.2,3 The metallic binder of cemented carbides is usually cobalt; however, when the application exposes the material to an acid environment, a nickel-based binder is favored for its better corrosion resistance. Another approach for improving corrosion resistance is to reduce the amount of binder,4 namely binderless carbides. This work focuses on Ni-bonded and binderless cemented carbides. All of these materials are nonmagnetic. The use of tungsten carbide materials in optical systems5 as either mold masters6 or mirrors7 is the motivation behind achieving nanoscale surface roughness from grinding and subsequently polishing. Surface roughness is closely related to the wear mechanism of the material. SEM images of the ground surfaces exposed the similarities between the wear behavior of Ni-bonded and Co-bonded materials, in particular, the formation of a deformed surface layer because of the extrusion of the nickel binder between the WC grains, as described for Co-bonded3