Effect of wire EDM machining (Teİ) process on the tribologicalbehavior of Invar 36 alloy

Invar is an iron-based nickel alloy. Invar 36 has a low thermal expansion coefficient as it contains 36% Nickel element. In this study, cutting of invar 36 alloy, which is preferred in aerospace, electronics, aviation and applications requiring high precision due to its low coefficient of thermal expansion, by WEDM cutting method was investigated. In the invar 36 alloy cut using a zinc-doped brass-coated copper wire electrode, a white layer consisting of molten workpiece and electrode residues was formed on the cut surface. This layer, called the white layer, is cleaned and the workpiece takes its final form. For this purpose, the White layer was removed with 800 grit sandpaper and the surface roughness (Ra) decreased from 3.12 μm to 0.32 μm, resulting in 90% improvement. SEM images and EDX analyzes of the treated surfaces were taken before and after sanding. It has been observed that there are O, Fe, NI, Cu and Zn residues on the processed surfaces before sanding, and that after sanding, the white layer is removed and electrode residues such as Cu and Zn are removed. In order to compare the hardness of the WEDM treated surface and the untreated surface, the hardness measurements were made using the Vikers method using 50, 200, 500 and 1000 gram weights from the sample. While the hardness values at the edges of the surface treated with WEDM were higher than the edges of the untreated surface, the hardness value in the middle parts of the treated surface was found to be less hard than the middle parts of the untreated surface. Since the dielectric liquid used in the WEDM process immediately removes the heat generated during the cutting process at the edges of the material, an increase in hardness occurred on the surface due to rapid cooling, while the heat generated in the middle parts of the material was removed later because the liquid reached late and could not reach it completely. As a result of this, a softer structure was obtained from the main material due to slow cooling in the middle part of the material. Wear volume loss of Invar 36 material cut with WEDM was less than that of untreated Invar 36 material. As a result of all the experiments, the friction and wear performance of the alloy on the surfaces cut with WEDM gave better results.