Microstructural Characterisation for Polycrystalline Nickel

Abstract

Polycrystalline Nickel has very good mechanical properties and excellent corrosion resistance. In this paper, we try to find the suitability of Nickel 200 for structural applications. The compression test on the specimens is carried out in the longitudinal and transverse directions and the difference in the strength in both the directions is studied before and after the heat treatment process. By investigation of the microstructure, the correlation between the deformation behaviour and grain morphology is investigated. The compression test results before the heat treatment reveal that by increasing the strain beyond the elastic limit, the material is anisotropic (up to 4 %). Also, the heat treatment analysis reveals that the sub-grains have occurred in the microstructure. Machining experiments have been performed on Nickel 200 to accomplish proper surface finish and dimensional accuracy. Machining results reveal that the process parameters will have a strong influence on cutting forces and surface roughness. The results showed a significant effect of the cutting speed interaction on cutting forces and surface roughness. An improvement of 38% in cutting forces was detected with increasing the cutting speed from 360 rpm to 450 rpm at constant feed rate (0.12 mm/rev) and depth of cut (0.1 mm). However, the surface roughness was almost constant for the increase in the cutting speed.