جستجوی مقالات مرتبط با کلیدواژه "سوپرآلیاژ اینکونل 738" در نشریات گروه "مواد و متالورژی"

This study aimed to investigate the effect of diffusion welding parameters on the microstructural characteristics and mechanical properties of the dissimilar joint between AISI 418 stainless steel and Inconel 738 superalloy using Ni interlayer with a thickness of 50 µm. The experiments were performed in a vacuum furnace at three temperatures of 1000, 1050 and 1150 °C for 45, 60, 75 and 90 min under the pressure of 5 MPa.The results show that voids and non-bonded areas are seen in the samples that were bonded at a lower temperature (1000 °C). By increasing the joining temperature from 1000 °C to 1050 °C, all micro discontinuities have disappeared, which shows that the microplastic deformation of roughness has improved. Then, by increasing the temperature to 1150 °C,non-bonded areas are observed in the joint due to the reduction of pressure on the contact surfaces. When pure nickel is used as an interlayer, intermetallic compounds of γ' [Ni3(Al, Ti)] are formed in the γ matrix phase on the side of Inconel 738 superalloy while compounds of FeNi3 and γ (γFe, Ni) are formed on the side of AISI 418 stainless steel. According to the results of line scan analysis, the slope and penetration of elements in Inconel 738 superalloy is lower than AISI 418 stainless steel , which indicates less penetration in Inconel 738 superalloy. In the sample welded at the temperature of 1050 °C and the time of  90 Min, the penetration value of the nickel interlayer in AISI 418 stainless steel  and Inconel 738 superalloy was 40 µm and 35 µm, respectively. By comparing the maximum hardness, it can be concluded that the joint at the temperature of 1050 °C and the time of 90 Min has a lower maximum hardness than other samples. Therefore, it has better joint characteristics than other samples in terms of intermetallic compounds. The highest value of shear strength was obtained at the temperature of 1050 °C and the time of 90 Min, which is equal to 270 MPa.

Inconel 738 superalloy is widely used for hot-section components of gas turbines. These hot-section components are exposed to an extremely oxidative environment at high temperatures and consequently their life span is dramatically decreased. Considering this problem, NiCrAlY coatings can be effectively used to protect the hotsection components. In this study, laser cladding process was used to coat a NiCrAlY alloy on the surface of Inconel 738 substrate for the purpose of improving the high-temperature oxidation resistance. In order to compare the oxidation behavior, oxidation tests at temperature of 1200 ˚C were individually conducted on Inconel 738 substrate and freestanding laser-cladded NiCrAlY coating. Laser cladding of NiCrAlY alloy resulted in the formation of hypo-eutectic dendritic γ/β structure. Moreover, the results of oxidation tests showed that the oxidation resistance of the laser-cladded coating was significantly better than that of Inconel 738 substrate and this coating can be an effective choice for protecting the hot-section components made of Inconel 738 superalloy.