Scanning electron microscopy (SEM) has been used to identify and analyse the secondary adhesion effect precursors formed during the dry drilling processes of Ti-6Al-4V alloy over the rake face and flute of the drilling tools. Subsequent analysis with energy dispersive spectroscopy (EDS) was enabled to distinguish its compositional characteristics. Thus, according to the EDS obtained data, a stratified multi built-up layer (MBUL) composed by TiOxis formed over the rake face of the tool. Furthermore, this multi-layer adhered allows initially the built-up edge (BUE) development close to the edge of the tool by a mechanical adhesion mechanism. In a second step, it is responsible for the formation of a thicker secondary BUL which avoids the chip flow, and it provokes the tool collapse. These mechanisms are different from those observed in the dry machining of other alloys such as steels, nickel-based alloys, or aluminium alloys.
An investigation of the material removal process in grinding glass and the effects of the grinding process on the surface structure and fracture strength of the finished product is reported in two papers. This first paper is concerned with the mechanics of material removal for grinding a large number of glasses and some glass-ceramics over a wide range of operating conditions with both silicon carbide and diamond grinding wheels. Experimental results indicate that the specific grinding energy generally increases with the softening temperature of the glass, and is an order of magnitude smaller for grinding with diamond wheels than for grinding with silicon carbide wheels. From observations of individual grinding scratches and an analysis of the experimental results, it is concluded that virtually all of the grinding energy is expended by viscous deformation. Material removal occurs by flow into chips with silicon carbide abrasive and by brittle fracture preceded by viscous deformation with diamond abrasive. The specific grinding energy with diamond is much less than with silicon carbide, since a much smaller volume of material undergoes viscous deformation when grinding with diamond.
An investigation is described of the surface structure and fracture strength for grinding of glass under various conditions. The surface structure of finished glass surfaces was examined by scanning electron microscopy. Surfaces ground using a silicon carbide wheel exhibited extensive flow over the surface, while surfaces ground with diamond wheels appeared to have been generated by brittle fracture with some evidence of localized flow. The relative amounts of flow and fracture on the diamond ground surfaces for various grinding conditions are related to the number of cutting points per unit area of finished surface. Grinding conditions resulting in relatively more flow were generally found to lead to higher fracture strengths.
Titanium based alloys, mainly UNS R56400 (Ti6Al4V), are increasingly being applied in the airship building industry due to its excellent physicochemical properties. Machining operations are usually required in the manufacturing processes of Ti based aerospace structural elements. However, high reactivity of Ti provokes a quick tool wear. So, in order to reach an economically acceptable production level, it is necessary to minimize the costs associated to tool wear. In this work, Scanning Electron Microscopy (SEM), Stereoscopic Optical Microscopy (SOM) and Energy Dispersive Spectroscopy (EDS) have been used for both analysing and identifying secondary adhesion mechanisms that are taking place when an aeronautical titanium alloy is machined. Special severe cutting conditions have been applied. Thus, titanium alloy have been dry machined with TiN coated WC-Co tools. Results obtained have shown that tool wear is controlled by a secondary adhesion mechanism, which presents two stages. A first stage is constituted by a TiOx multi-film formed onto the tool surfaces. A second step involves the mechanical adhesion of the alloy material to those surfaces. When this material is removed, tool particles are dragged off causing tool wear.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.