Ageing Characterization of the Power Metallurgy Superalloy N18

Abstract

The ageing process of the powder metallurgy superalloy N18 has been investigated. This alloy exhibits a two-phase microstructure with a long range L12 ordered multimodal ' precipitation. N18 has been designed for high temperature turboengine disks applications. Superalloys however, are prone to microstructure evolution when sustained at high temperature since ' precipitates are coarsening. A method based on scanning electron microscope (SEM) image analysis is developed to qualify and quantify the material ageing. Two kinds of ageing have been considered: material temperature exposure with and without mechanical loading application. A short term quantitative law considering precipitates size, ageing time and temperature is established. In addition a long term behavior in agreement with our measurements is suggested.

The Effects of Heat Treatment and Microstructure Variations on Disk Superalloy Properties at High Temperature

“…These trends provided insights into the interrelationships among the various processing parameters and the γ S ′ and γ T ′ sizes and area fractions. The relative stability of γ S ′ size during aging has been reported for disk superalloys of lower γ ′ content [14,15]. No splitting of γ S ′ [16] was evident for the short aging times examined here.…”

“…No splitting of γ S ′ [16] was evident for the short aging times examined here. LSW coarsening of γ T ′ in disk superalloys during aging was also reported in several studies [15,16,17]. However, the effects of cooling rate on γ T ′ coarsening response and relative γ S ′ versus γ T ′ phase volume fractions were unexpected.…”

Effect of calcination temperature on the structure and catalytic performance of copper–ceria mixed oxide catalysts in phenol hydroxylation

“…It is clear that the crystallite size values of the samples are found to increase from 8 to 28.7 nm with increasing in calcination temperatures from 400 to 800 C. This increase in crystallite size may be attributed to the Oswald ripening process assisted by the elevated temperature, this a diffusion process where the particles are getting bigger and bigger at the expense of small particles as described elsewhere. 31 Compared to XRD patterns of the pure CeO 2 , the diffraction peaks of the CuO@CeO 2 samples shied to lower angles (inset, Fig. 2).…”

Impact of the Solution Cooling Rate and of Thermal Aging on the Creep Properties of the New Cast & Wrought Rene 65 Ni-Based Superalloy

“…The activation energy here obtained for R65 (Q = 358 kJ.mol-1) is in quite good agreement with other forged Ni-based superalloys. Indeed, as an example, the activation energy reaches 335±6 kJ/mol for the growth of tertiary y' in N18 alloy [16].…”