A novel codeposition process has been developed for the fabrication of inhomogeneous optical coatings. These single-layer coatings exhibit composition and refractive index that vary continuously with thickness. Two types of inhomogeneous optical filters for antireflection and narrow band rejection applications, respectively, were experimentally fabricated using different vacuum deposition processes. The antireflection coating, composed of ZrO2 and MgF2, was prepared by electron beam coevaporation. The narrow band rejection filter, made up of SiO2 and TiO2, was codeposited by ion assisted, dual ion beam sputtering technique. The physical, chemical, and microstructural characteristics, as well as optical and environmental properties of these filters were evaluated.

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Machining quality and productivity of superalloys are limited due to their poor machinability, and fewer studies have focused on the cutting of iron-based superalloys. In this study, the cutting performance of coated and uncoated carbide tools in high-speed dry turning iron-based superalloy GH2132 was investigated by performing a series of cutting experiments. The experimental results indicated that cutting temperature and cutting forces increased, while tool life decreased with the increase in the cutting speed from 30 to 100 m/min. Under relatively low cutting speeds, flank face wear was dominated by abrasion and adhesion, while rake face wear mainly involved built-up edge (BUE), built-up layer (BUL), adhesion, and breakage near the depth of cut. Under higher cutting speed, adhesion wear was more serious on the flank face, and peeling off of the coatings and substrate occurred on the rake face. Owing to the protective effect of (Ti, Al)N + TiN coating, the coated tools exhibited better wear resistance and thus longer tool life, in particular, under higher cutting speeds. Analysis of the tool wear gap in the horizontal direction indicates that better dimensional accuracy could be obtained when coated tools are used. In dry turning of GH2132 with carbide tools, a favorable surface finish could be obtained. The surface roughness roughly showed a tendency to first decrease and then increase with the increase in average flank wear. The coated tools should be avoided to machine GH2132 at higher cutting speed due to the poor surface finish.

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