Evaluation of Metallurgical Quality of Master Heat IN-713C Nickel Alloy Ingots

Abstract

The paper presents the results of evaluation of the metallurgical quality of master heat ingots and of the identification of non-metallic inclusions (oxides of Al., Zr, Hf, Cr, etc.), which have been found in the shrinkage cavities formed in these ingots. The inclusions penetrate into the liquid alloy, and on pouring of mould are transferred to the casting, especially when the filtering system is not sufficiently effective. The specific nature of the melting process of nickel and cobalt alloys, carried out in vacuum induction furnaces, excludes the possibility of alloy refining and slag removal from the melt surface. Therefore, to improve the quality of castings (parts of aircraft engines), it is so important to evaluate the quality of ingots before charging them into the crucible of an induction furnace. It has been proved that one of the methods for rapid quality evaluation is an ATD analysis of the sample solidification process, where samples are taken from different areas of the master heat ingot. The evaluation is based on a set of parameters plotted on the graph of the dT/dt derivative curve during the last stage of the solidification process in a range from TEut to Tsol.

Impact of a Structure on Durability of Modified Nickel-Base Superalloys in Creep Conditions/ Wpływ Struktury Na Trwałość W Warunkach Pełzania Modyfikowanych Nadstopów Na Bazie Niklu

“…2). Additional effect of this method was double alloy filtration [9]. In addition parts of casting made in experiment 4 were subjected to precipitation hardening heat treatment ( solutionizing at 1185…”

“…In case of cast nickel superalloys it is particularly important to assess the impact of the chemical composition, casting conditions and grain size modification processes, all of which determine the morphology of macroand microstructure, on the stability in the conditions of creep tests [6][7][8][9] for these tests provide information about the behaviour of material in extreme working conditions. Different mechanisms of creep are often observed during the short and long-term creep tests [8][9][10][11]. In general, the dislocation creep dominate in the short-term trials, whereas diffusion creep (Nabarro-Herring and Coble creep) usually dominate in the long-term studies [10][11][12][13][14][15].…”

“…Such structure can be the cause of formation and propagation of cracks and thus cause serious accidents. One of the methods of structure improvement is surface [16] and volume [8,9,17,18] modification. [12] This study assessed the effect of surface and volume modification and double filtration during pouring on the stability under accelerated creep of castings made from scrap IN-713C and MAR-247 nickel superalloys.…”

Creep Behaviour of Modified Mar-247 Superalloy

“…Modification mixture contained cobalt aluminate CoAl 2 O 4 which gave it characteristically blue colour, hence the naming "blue" and "white". Moulds were prepared according to procedures of combined volume and surface modification with double filtration [16][17][18].…”

“…In case of the turbine blades, the good understanding of cracking in creep conditions allows for proper selection of materials, modification and heat treatment procedures and thus obtain optimal material characteristics such as microstructure and mechanical properties. Some of the methods of structure refinement are the surface [11][12][13], volume [14][15][16] and combined surface and volume modification techniques [17,18]. This processes allow for obtaining grains of various dimensions, orientation and distribution.…”