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Evaluation of metallurgical quality of master heat IN-713C nickel alloy ingots

Binczyk F., Cwajna J., Roskosz S., Gradoń P.

Archives of Foundry Engineering

2012

Vol. 12, iss. 4

5-10

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.

The ATD thermal analysis of selected nickel superalloys

Binczyk F., Śleziona J.

Archives of Foundry Engineering

2010

Vol. 10, iss. 2

13--18

The study presents the results of the ATD thermal analysis made on selected nickel alloys used by WSK Rzeszów for parts of aircraft engines. The aim of the studies was investigation of solidification parameters, especially Tlik and Tsol. The said parameters are very important in the determination of pouring temperature and maximum operating temperature of castings. Another important technical information is the quality of "master heat" ingots, examined for the stability of chemical composition and presence of different impurities. It has been concluded that the pouring temperature of CMSX-4 and MAR-247 alloys should be comprised in a range from 1470 to 1480°C, while for the remaining alloys the recommended range of pouring temperatures is from 1440 to 1450°C. Examinations have also proved that some batches of the supplied ingots are contaminated with non-metallic impurities, located mainly in the region of shrinkage cavities.

Effect of repeated remelting on the chemical composition and structure of nickel alloys

Binczyk F., Śleziona J., Mikuszewski T.

Archives of Foundry Engineering

2010

Vol. 10, iss. 1 spec.

189--194

The results of preliminary tests and studies on the effect of repeated remelting of selected nickel alloys on changes in the chemical composition and structure were presented. The aim was to investigate possible management and utilisation of post-production waste (rejects, parts of the gating system, etc.). It has been reported that repeated remelting of IN-713C alloy had no significant effect on changes in its chemical composition. Only aluminium slightly reduced its content due to melting loss, as confirmed further by the results of ATD thermal analysis. On the other hand, in MAR-247 alloy after remelting, a decrease in the content of Cr, Ta, Hf, and C in particular, was observed. To re-use the post-production waste, it is necessary to make up the content of some elements (especially trace elements) and carry out the modification process.