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This paper compares and analyzes the oxidation behavior of Ni-base alloyswith and without about 2.7 wt.% Si addition. The Ni-base alloys studied were of two types: cast model alloys or wrought commercial alloys. Oxidation testing was conducted at 1000 • C in still air. The specific aspects studied were scale spallation resistance, nature by which the silicon oxidized, and the influence of silicon on the subsurface depletion behavior of chromium. From oxidation results of the cast model alloys, Si addition was found to improve oxidation resistance by forming a continuous SiO 2 layer at the alloy/scale interface, which resulted in decreased oxidation kinetics. The cast alloys with Si addition also showed larger average effective interdiffusion coefficients of chromium compared to the cast alloys without Si addition. As a consequence, the Si addition assisted in the establishment and re-formation of a chromia scale during oxidation. In the case of the wrought commercial alloys, a discontinuous distribution of SiO 2 precipitates in the vicinity of the alloy/scale interface was found to be beneficial to cyclic oxidation resistance.KEY WORDS: high temperature oxidation; silicon effect; chromia-former; Ni-base alloy; chromium depletion and interdiffusion behavior.

Great advance has been witnessed in image-based particle size and shape characterisation methods for reproducing traditional sieve-based size and caliper-based shape measurements. However, discrepancies still existed due to the limitations of image-based methods, which include the difficulty of obtaining the third dimensions from two-dimensional images, the errors caused by the internal textures of particles, and the particle shadows due to non-uniform illumination. This paper presents a simple, effective and inexpensive structural light technique for eliminating these limitations. This technique can determine three principal dimensions of many sand to gravel particles simultaneously and is less affected by particle internal textures and shadows. Eight hundred randomly selected soil particles with a range of sizes, colours, shapes and angularities were investigated using the structural light system to obtain their size and shape distributions. A remarkable agreement was found between the structural light results when compared with sieving analysis and manual measurement of shapes using calipers.

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