The paper presents the results of studies on the development of correlation of solidification parameters and chemical composition of nickel

superalloy IN-713C, which is used i.a. on aircraft engine turbine blades. Previous test results indicate significant differences in

solidification parameters of the alloy, especially the temperatures Tliq and Tsol for each batch of ingots supplied by the manufacturer.

Knowledge of such a relationship has important practical significance, because of the ability to asses and correct the temperatures

of casting and heat treatment of casts on the basis of chemical composition. Using the statistical analysis it was found that the temperature

of the solidification beginning Tliq is mostly influenced by the addition of carbon (similar to iron alloys). The additions of Al and Nb have

smaller but still significant impact. Other alloying components do not have significant effect on Tliq. The temperature Teut is mostly

affected by Ni, Ti and Nb. The temperature Tsol is not in any direct correlation with the chemical composition, which is consistent with

previous research. The temperature Tsol depends primarily on the presence of non-metallic inclusions present in feed materials and

introduced during the melting and casting processes.

The paper presents the results of research on the determination of the effect of pouring temperature on the macrostructure of the castings

subjected to complex (surface and volume) modification and double filtration. Tested castings were made of post-production scrap (gating

system parts) of IN-713C superalloy. Tests included the evaluation of the number of grains per 1 mm2

, mean grain surface area, shape

factor and tensile strength. Casting temperature below 1470 °C positively influenced the modification effect. The grains were finer and the

mechanical properties increased, especially for castings with thicker walls. On the other hand, manufacture of thin walled castings of high

quality require pouring temperature above 1480 °C.

In current casting technology of cored, thin walled castings, the modifying coating is applied on the surface of wax pattern and, after the

removal of the wax, is transferred to inner mould surface. This way the modification leading to grain refinement occur on the surface of

the casting. In thin walled castings the modification effect can also be seen on the other (external) side of the casting. Proper reproduction

of details in thin walled castings require high pouring temperature which intensify the chemical reactions on the mould – molten metal

interface. This may lead to degradation of the surface of the castings. The core modification process is thought to circumvent this problem.

The modifying coating is applied to the surface of the core. The degradation of internal surface of the casting is less relevant. The most

important factor in this technology is “trough” modification – obtaining fine grained structure on the surface opposite to the surface

reproduced by the core.

Paper presents the results of research on modified surface grain refinement method used in investment casting of hollow, thin-walled parts

made of nickel based superalloys. In the current technology, the refining inoculant is applied to the surface of the wax pattern and then, it

is transferred to the ceramic mould surface during dewaxing. Because of its chemical activity the inoculant may react with the liquid metal

which can cause defects on the external surface of the cast part. The method proposed in the paper aims to reduce the risk of external

surface defects by applying the grain refiner only to the ceramic core which shapes the internal surface of the hollow casting. In case of

thin-walled parts the grain refinement effect is visible throughout the thickness of the walls. The method is meant to be used when internal

surface finish is less important, like for example, aircraft engine turbine blades, where the hollowing of the cast is mainly used to lower the

weight and aid in cooling during operation.

The paper presents the results concerning impact of modification (volume and surface techniques), pouring temperature and mould

temperature on stereological parameters of macrostructure in IN713C castings made using post-production scrap. The ability to adjust the

grain size is one of the main issues in the manufacturing of different nickel superalloy castings used in aircraft engines. By increasing the

grain size one can increase the mechanical properties, like diffusion creep resistance, in higher temperatures. The fine grained castings. on

the other hand, have higher mechanical properties in lower temperatures and higher resistance to thermal fatigue. The test moulds used in

this study, supplied by Pratt and Whitney Rzeszow, are ordinarily used to cast the samples for tensile stress testing. Volume modification

was carried out using the patented filter containing cobalt aluminate. The macrostructure was described using the number of grains per

mm2

, mean grain surface area and shape index. Obtained results show strong relationship between the modification technique, pouring

temperature and grain size. There was no significant impact of mould temperature on macrostructure.