Institute of Fundamental Technological Research

Direct Metal Laser Sintered Haynes 282 specimens as well as wrought ones were subjected to high-temperature exposure at 1000 °C for 100h in air to compare their oxidation behaviour. The specimens were removed from the furnace after 1h, 5h, 25h, 50h and 100h to reveal and study oxidation mechanisms through morphological and cross-sectional examination by using scanning electron microscopy with energy dispersive spectroscopy attachment and X-ray diffraction. Microstructural studies revealed that the oxidation kinetics, determined by changes in thickness scale and depth of aluminium diffusion zone, were mainly driven by the formation of Cr2O3 for the wrought material, and TiO2 for DMLS one. The wrought material was characterized by the oxidation rate equal to 0.96 and followed the logarithmic law. On the other hand, DMLS-manufactured Haynes 282 exhibited oxidation rate of 0.90 and follows the linear law for the thickness scale considerations. However, when the depth of aluminium diffusion was investigated, it had an oxidation rate of 0.87 and followed cubic law.

The fatigue response and high-temperature corrosion resistance of Inconel 740 nickel alloy in its as-received state, and the same material with aluminized surface layer, were investigated. The aluminized layer was applied by using the chemical vapor deposition process with the participation of AlCl3 vapors under a hydrogen protective atmosphere at a temperature of 1040°C for 8 h and internal pressure of 150 hPa. The microstructure of the aluminized layer was characterized through scanning electron microscopy and x-ray energy dispersive spectroscopy analysis. It was found that Inconel 740 with an aluminized surface exhibited an improved hardness and fatigue response of 100 MPa in the whole range of stress amplitudes from 350 MPa to 650 MPa. Additionally, the application of the aluminization process enhanced service life as well as the corrosion resistance of the alloy in question and effectively protected it against high-temperature corrosion.

With the rising demands of industry to increase the working temperature of gas turbine blades and internal combustion engines, thermal barrier coatings (TBC) were found to be an effective way to further enhance the lifetime of aero components through the improvement of mechanical properties and oxidation-resistance. Thus, this paper aims to review coating technologies with special emphasis on plasma-sprayed thermal barrier coatings (PS), and those produced by physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods. Each technology was assessed in terms of its effectiveness to enhance the mechanical response and oxidation resistance of nickel-based parts working at high temperature. The effect of coating technology on mechanical strength, hardness, fatigue and creep of nickel alloys was discussed to reveal the potential candidates for future applications in aggressive environments

high temperature corrosion, fatigue, creep, aggressive environment, turbine blade

The paper presents a comparison of microhardness, fatigue and high temperature corrosion of Inconel 740H nickel alloy in its as-received state and the same material with nitrided surface layers. The nitrided layers were produced using traditional glow discharge nitriding (specimens nitriding on the cathode potential) and an active screen (specimens nitriding at the plasma potential). A microstructure of the layers was characterized through the scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray diffraction analysis. Mechanical properties of the nitrided Inconel 740H alloy were examined using microhardness measurements and standard fatigue tests. It was found that Inconel 740H with a nitrided surface exhibited an improved fatigue response of 50 MPa in the whole range of stress amplitudes from 350 to 650 MPa and almost 325% increase of hardness for plasma modified surface and 250% for cathode modified surface. Additionally, the application of cathode nitriding enhanced the corrosion resistance of the alloy in question and effectively protected it against a high temperature oxidation.

nitriding, nickel alloys, coatings, fatigue, corrosion

In this paper, the LENS technique with optimized parameters was applied to investigate the feasibility of Inconel 625 repair process. The process was performed on the substrate material heated to 300 ◦C at laser power of 550 W. Subsequently, the specimens were subjected to microhardness and three-point bending tests to assess the effectiveness of the repair system. The results showed that the mechanical properties of the Inconel 625 specimens repaired by using the LENS system were similar or even better than those of the substrate material.

LENS technology, Inconel alloys, repair process, additive manufacturing

In this paper, the Inconel 625 laser clads characterized by microstructural homogeneity due to the application of the Laser Engineered Net Shaping (LENS, Optomec, Albuquerque, NM, USA) technology were studied in detail. The optimized LENS process parameters (laser power of 550 W, powder flow rate of 19.9 g/min, and heating of the substrate to 300 °C) enabled to deposit defect-free laser cladding. Additionally, the laser clad was applied in at least three layers on the repairing place. The deposited laser clads were characterized by slightly higher mechanical properties in comparison to the Inconel 625 substrate material. Microscopic observations and X-ray Tomography (XRT, Nikon Corporation, Tokyo, Japan) confirmed, that the substrate and cladding interface zone exhibited a defect-free structure. Mechanical properties and flexural strength of the laser cladding were examined using microhardness and three-point bending tests. It was concluded, that the LENS technology could be successfully applied for the repair since a similar strain distribution was found after Digital Image Correlation measurements during three-point bending tests.

LENS technology, Inconel alloys, repair process, additive manufacturing

W niniejszej pracy zaproponowano wykorzystanie metody LENS do regeneracji modelowych elementów wykonanych ze stopu Inconel 625. Podczas badań wstępnych użyto sferycznego proszku ze stopu Inconel 625 o wielkości cząstek z przedziału 50-100 um oraz materiału podłoża wykonanego z tego samego materiału. Próby regeneracji przeprowadzono z użyciem lasera o mocy 550 W przy szybkości podawania proszku równej 12 RPM. Zastosowano trzy różne metody wypełniania modelowych ubytków, tj.: wypełnienie bez konturu (tylko w objętości modelowego ubytku), wypełnienie z konturem i w objętości ubytku oraz wypełnieniem tylko w postaci konturu. Po przeprowadzonych badaniach stwierdzono, że regeneracja powinna przebiegać na podgrzewanym podłożu, a proces napawania należy realizować w więcej niż dwóch przejściach, co do grubości napoiny.

technologie laserowe 3D, regeneracja, LENS (Laser Engineered Net Shaping), techniki przyrostowe

inconel alloys, repair process, additive manufacturing

inconel alloys, repair process, additive manufacturing

LENS, wytwarzanie przyrostowe, stopy niklu, stopy tytanu, regeneracja

LENS, additive manufacturing, Inconel 625, repair process