VDM NICKEL 200

VDM Nickel 200 is an unalloyed nickel grade that contains at least 99.2% nickel. It has characteristics that are useful in several fields, notably chemical processing and electronics. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Ni-778. Producer or source: VDM Metals GmbH (a subsidiary of Acerinox, S.A.).

MICROSTRUCTURAL CHARACTERISATION FOR POLYCRYSTALLINE NICKEL

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.

Strain Behavior of Nickel Alloy 200 during Multiaxial Forging through Finite Element Modeling

Multiaxial forging (MAF) is one of the appealing methods of severe plastic deformation (SPD) techniques to fabricate ultrafine-grained (UFG) materials. In this study; the influence of process parameters such as strain rate; friction; and initial temperature has been assessed through finite element simulation of Nickel 200 alloy. The Johnson–Cook equation was applied in simulating the MAF process. The homogeneous microstructure of a material processed by MAF is an important requirement to obtain uniform mechanical and other properties. The uniformity in properties was evaluated by the investigation of the hardness measurements; effective strain (ES), and inhomogeneous factor (IF) or coefficient of standard deviation. The results showed that the inhomogeneous factor decreases with an increase in strain rate and decrease in temperature. It was found that a more homogeneous structure is observed with an increasing number of MAF cycles and the strain rate strain. Furthermore; the average grain size reduced from 850 nm to 220 nm after three cycles of MAF. Finally; experimental work was performed to validate the results.

Peak broadening anisotropy in deformed face-centred cubic and hexagonal close-packed alloys

The broadening of diffraction peaks representing different families of grain orientations has been measured for a number of deformed metals: austenitic stainless steel 316, nickel 200 and the titanium alloy Ti-6Al-4V. These measurements have been compared with predictions that explain differences in broadening in terms of the contrast factor of dislocationsviatwo different approaches. This was done in order to understand the effect the contrast factor has on the results of diffraction peak profile analysis methods and the cause of broadening anisotropy. An approach that considers all grains and orientations to behave similarly was found to be unsuccessful in explaining the large variations of broadening in different peaks. These variations can be explained, and errors reduced, by adopting an approach that uses a polycrystal plasticity model. However, if the plasticity based approach is used to solely calculate changes in the contrast factor, it only partly explains changes in broadening. Instead, factors such as variations in the dislocation density and crystallite size in different orientations, the number of dislocations that are mobile, and the number of edge and screw dislocations need consideration. The way to incorporate these additional factors is difficult, but their contribution to broadening anisotropy can be as important as that of the contrast factor.

Study of Recovery and Recrystallisation in a Folded Al Alloy

Changes in the microstructure and crystallographic orientations during in-situ heating of folded Al 0.1%Mg have been followed by SEM and EBSD. The folding process results in both strain and texture gradients across the folded region which in turn can influence the recovery and recrystallisation processes as well as crystallographic texture. This work is an extension of ex-situ heating experiments on folded nickel 200, titanium and ferritic steel [1,2]. The present findings illustrates that during isothermal in-situ heating at 295oC nucleation and growth starts close to the surface where the deformation is highest, new grains form and grow in a region about quarter depth of the sheet thickness. After this grain growth occurs resulting in large grains that meet up at the centre line. These results are consistent with those found in ex-situ heated Ni200 alloy [2], where fine grains were found in the compressed and tensile regions with large grains in the middle of the sheet.

Failure Analysis and Fitness-for-Service Assessment of Nickel 200 Baffles in PVC Reactor

Visual inspection of Nickel 200 (Ni-200) baffles inside several Type 304L reactor vessels used to produce PVC revealed corrosion in the form of localized metal loss along the baffle’s length direction. Prior to recent process changes, these baffles had operated satisfactorily for about 8 years. The observation of metal loss raised concerns as to the cause of the corrosion, and the possibility of compromised structural integrity of the reactor baffles. A failure analysis was performed to characterize the nature and extent of the corrosion, based on scrape samples and cut-out samples. A Level 3 fitness-for-service assessment per API 579 was performed to evaluate the urgency for repairs. Laboratory corrosion testing was then done to further investigate the influence of pH, oxygen, and temperature, on the corrosion susceptibility of the Ni-200 material in this application.