Since the cutting tools used in machining process of super alloys are subjected to high cutting forces, accordingly tools life is reduced, therefore improvement in alloys machining and reducing cutting forces to achieve longer tools life is an essential necessity. In this research, the effect of changes in feed rate on cutting forces in machining process of nickel based super alloys is investigated. Cutting tools used in this experiment was a tungsten carbide material, model 890, geometry square shaped and specification of SNMG 120412. Also the tools has been coated using physical vapor deposition by chemical composition of TiN/TiCN/AlTiSiN in both micro and nano layer conditions. According to the results, as the feed rate is increased cutting forces mostly increases in both micro and nano layer coating conditions.. Generally in this research, application of micro layer coating results in less cutting forces compared to nano layer coating, so it can be said that micro layer coating has a better performance.

The effect of ultrasonic impact treatment (UIT) was studied on the microstructure and corrosion behavior of Haynes 25 superalloy. The UIT was performed at a frequency of 20 kHz, tool feeding rates of 0.08, 0.12, and 0.16 mm/rev, vibration amplitudes of 10, 28, and 50% of the machine power, static pressures of 0.1 and 0.9 bar at the different number of passes (one, two, three, five, and seven). According to the results, the UIT severely deformed the surface layers up to a depth of about 100 μm and promoted the emergence of deformation bands/strain-induced martensite (-phase) up to a depth of about 400 μm. The UIT also produced ultrafine grain structure in the surface region and due to the deformation inhomogeneity developed surface compressive residual stresses. The Tafel polarization tests indicated that applying one pass UIT at the static pressures of 0.1 and 0.9 bar reduced the corrosion current (from 4.16 A/cm2 to 1.3 A/cm2 and 2.18 A/cm2, respectively), and the corrosion potential (from -0.6 V to -0.7 V and -0.8 V, respectively). This behavior was found to be due to promotion of surface oxidation and formation of protective layer on the surface. Despite increasing the surface smoothness, further increasing the UIT pass number to seven, probably due to encouraging the formation of surface pits/microcracks increased the corrosion current and corrosion rate by about 45%. According to the electrochemical impedance tests, at the static pressure of 0.9 bar, the as-received and seven-pass UITed samples showed the lowest corrosion resistance whilst one-pass and two-pass UITed samples revealed the highest corrosion resistance. The effect of tool feeding rate on the corrosion resistance was found to be minor.

The swirler of the gas turbine combustion chamber is usually designed from nickel-based superalloys and produced by the conventional precision casting method under vacuum. The production of such parts is associated with high scrap due to geometrical complexity, high dimensional accuracy and also the use of ceramic cores. In recent decades, the use of the additive manufacturing process as a new and alternative method has been growing for the production of complex metal parts in the power plant industry. In this research, a gas turbine Swirler and several Inconel 625 samples were fabricated by SLM in optimal conditions of the main variables of the manufacturing process such as laser power, scanning speed and the thickness of the melted layer. Microstructural studies were performed by optical Microscope on samples and some structural defects such as incomplete local melting, porosity, non-metallic oxide phases and Microcracks were identified. The printed swirler was compared with the computer model in all important and final Surfaces by non-contact dimensioning method. The surface quality and dimensional accuracy of the part were acceptable and it was evaluated within the tolerance range of the casting part. Also, hardness and tensile tests at ambient temperature were performed on the heat treated samples. The results showed that the values of the tensile properties of the printed samples were higher in the parameters of yield strength and ultimate strength, but lower in the parameter of relative elongation and the hardness was also the same.

At this paper, a new equation has been presented to calculate the electrical resistance caused by constriction and presence of surface films on the sheets in small scale resistance spot welding. Then, the simulations have been conducted using the new model and its validity has been evaluated. Experimental verification was carried out on sheets made of Hastelloy X and it was found that the experimental nugget diameters have a good agreement with the results of the simulation. The maximum nugget diameter was created in the case of thin film. Also, existence of film layer improves tensile strength. At the presence of thick film the height of the weld is maximum that can be due to expulsion.

In this paper, static strength analysis of superalloy Rene-80 is studied experimentally in both of the coated and uncoated cases. Superalloy Rene-80 is widely used in manufacturing aircraft turbine blades. The service temperature of this alloy is in the range of 760– 982 ° C. Although this superalloy has good mechanical properties and acceptable protection against oxidation and hot corrosion, it is coated to improve its resistance to surface degradation factors such as oxidation, hot corrosion and erosion at high temperatures. In this paper, penetrating aluminide coatings were applied to this superalloy with two separate methods of penetration-powder and penetration-slurry, respectively, under the brand names Codep-B and IP1041slurry, respectively and the effect of these coatings on the tensile properties of Rene-80 under ehe temperature range of 25-982 ° C was investigated. For this purpose, the samples according to ASTM-E8 standard are produced and after coating (the two methods mentioned above) along with uncoated samples are carried out a tensile testing in accordance with the ASTM-E21 standard. The results of the present study showed that at low operating temperatures, uncoated samples have better tensile strength than coated samples, but this behavior is reversed at high operating temperatures, which indicates the importance of using nickel-based superalloy coatings for extreme heat environments. Also, the model with IP1041slurry coating at high operating temperature has better yield and ultimate strengths than powder penetration coating.

This study investigates the effect of ultrasonic impact treatment (UIT) on the surface structure, microhardness, and tribological behavior of L-605 superalloy. The surface of the samples was impacted by a high-frequency (20 kHz) spherical tungsten carbide tool for one, two, three, and five passes, using a feed rate of 0.08 mm/min, vibration amplitude of 28 %, and static pressure of 0.1 MPa. Results showed that UIT significantly deformed the surface microstructure and enhanced surface microhardness, primarily due to work hardening, strain-induced martensitic transformation, and ultrafine grain formation. A single UIT pass notably improved wear resistance and reduced the friction coefficient. Compared to the annealed alloy, the one-pass UITed samples showed wear rate reductions of 74%, 70%, 68%, and 64% under loads of 5, 10, 25, and 75 N, respectively. The average friction coefficient also dropped by up to 80% at 10 N and 74% at 75 N. Additional UIT passes resulted in marginal microhardness improvement, likely due to strain hardening saturation in the surface layers.

Size, shape, volume fraction and distribution of embedded γ / phase in γ phase has direct effect on strength of INCONEL alloy. Microstructure parameters of INCONEL phases are quantified from microstructure images using transmission electron microscopy (TEM). Different TEM sample preparation techniques were used to study INCONEL 738 alloy microstructure for transmission electron microscopy (TEM). The INCONEL 738 was first cut into a 1 × 1 cm slice with 600 μ m thickness with diamond wire cut. INCONEL sample was mounted by wax (M135), after initial grinding and polishing. The molded INCONEL sample was further polished by different grit size SiC paper to reduce the thickness below 80 micron. At this stage, 3 mm discs were cut from the thin slice of INCONEL alloy by mechanical punch machine. The 3 mm discs of INCONEL alloy were used for TEM sample preparation. Three methods of electro-jet polishing, ion milling and micro control dimpling were employed to prepare transparent TEM sample to observe the surface microstructure details of INCONEL 738 alloy. Electro-jet polishing TEM sample preparation technique could reveal microstructure details of INCONEL alloy γ and γ / phases using 42% H3PO4, 34% H2SO4, 24% H2O electrolyte at about – 400C bath temperature and applied voltage of 30 V.

The present study investigates the oxidation behavior of GTD-111 nickel base superalloy at 1000 °C in air. To this aim, several techniques including thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), grazing incidence X-ray diffraction (GI-XRD) and glow discharge optical emission spectroscopy (GDOES) were employed. The oxidation kinetics of this superalloy alters from linear to parabolic after 10 h exposure which is accompanied by the formation of a uniform surface oxide layer. Based on the cross-sectional analysis of FE-SEM and GDOES, Ti can most probably be considered as the first species which enters the reaction front when oxidation begins. However, as a result of its oxidation, Ti is depleted just beneath the oxide scale, and conditions changes in favor of the formation of other oxides, namely, Cr2O3. Subsequently, due to the internal diffusion of O2- species, Al is internally oxidized, and islands of Al2O3 form underneath the oxide layer. After 100 h of oxidation, the chemical composition of the oxide film consists of an Al-rich inner region, a Ti-rich outer region, and a Cr-rich intermediate layer. GI-XRD results also confirmed the formation of mentioned oxide phases. No indication of oxide spallation and formation of nickel oxides were observed even after 100 h of oxidation.

In the present study, the microstructural changes of a Nickel based superalloy Nimonic 80A during a non-isothermal deformation were studied. Therefore, microstructure evolution during hot side pressing test was predicted with combined methods of finite element analysis and processing map of the material. The predicted results were validated through experimental microstructural studies. The results show that the distribution of deformation parameters (i.e. strain, strain rate, and temperature) is non-uniform in the deformed samples. The severity of this non-uniformity depends on the amount of sample reduction. High reduction value at one step forging can cause flow localization and non-uniform dynamic recrystallization, which results the formation of adiabatic shear bands, while using the lower reduction value at each forging step, leads to more uniformly distribution of the deformation parameters and thus uniform the dynamic recrystallization with the stable flow. Hence the workability and microstructure of the Nimonic 80A alloy are mainly depends on the deformation path.