High Temperature Fatigue of Aged Heavy Section Austenitic Stainless Steels

This work investigates two austenitic stainless steels, Sanicro 25 which is a candidate for high temperature heavy section components of future power plants and Esshete 1250 which is used as a reference material. The alloys were subjected to out-of-phase (OP) thermomechanical fatigue (TMF) testing under strain-control in the temperature range of 100 ∘C to 650 ∘C. Both unaged and aged (650 ∘C, 3000 h) TMF specimens were tested to simulate service degradation resulting from long-term usage. The scanning electron microscopy methods electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were used to analyse and discuss active failure and deformation mechanisms. The Sanicro 25 results show that the aged specimens suffered increased plastic straining and shorter TMF-life compared to the unaged specimens. The difference in TMF-life of the two test conditions was attributed to an accelerated microstructural evolution that provided decreased the effectiveness for impeding dislocation motion. Ageing did not affect the OP-TMF life of the reference material, Esshete 1250. However, the structural stability and its resistance for cyclic deformation was greatly reduced due to coarsening and cracking of the strengthening niobium carbide precipitates. Sanicro 25 showed the higher structural stability during OP-TMF testing compare with the reference material.

Experimental investigation on powder processing and its flow properties of AlSi10Mg alloy with niobium carbide for additive manufacturing

In this study, aluminium-silicon alloy AlSi10Mg powder of spherical morphology was mixed with niobium carbide powder had irregular morphology in weight percentages of 2, 4, 6 and 8 and processed in a planetary ball mill apparatus. The optimal conditions for powder processing were a mixing time of 1.95 h and a speed of 71 RPM without milling balls. The use of milling balls was avoided to maintain the morphology of AlSi10Mg from degradation and improve the flowability of composite powder. To evaluate the flowability of processed powders, flow properties such as apparent density, tapped density, Hausner’s ratio, Carr index, static angle of repose and Hall flow rate were determined. Selective laser melting was used to fabricate AlSi10Mg composite specimens with varying percentages of niobium carbide. Finally, at 6% niobium carbide, the selective laser melting cube specimen had a maximum relative density of 99.21%.

Cobalt–Niobium-Carbide Eutectic Alloys for Increasing the Service Life of Gas Turbine Engines

This article represents the stages of the creation of new serial wear-proof and heat-resistant (at temperatures up to 1100 °C) cobalt–Nb-carbide cast eutectic alloys of the KhTN (XTN) grade at the G.V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, comparing them by their main properties, and use in aircraft engine engineering.

The Precipitation of Niobium Carbide and Its Influence on the Structure of HT250 for Automobile Wheel Hubs

Improving the strength of grey cast iron wheel hubs will improve the safety of automobiles and have a great significance for energy saving and environmental protection. This paper systematically compares the calculation results of Python-based precipitation calculation and JmatPro software simulation with experiments. The results show that with a low mass fraction of niobium (0.098%) cuboid Niobium Carbide (NbC) precipitates do not form in the liquid phase; however, an elongated NbC niobium-rich phase may form during the solidification process and in the solid phase. However, cuboid NbC precipitates can be precipitated from the liquid phase when the niobium mass fraction is higher (0.27%, 0.46%). These results indicate that with the increasing niobium content the amount, particle size, and initial precipitation temperature of niobium carbide precipitated in the matrix structure will increase. According to the observation and statistical analysis of the microstructure, it is found that tensile strength will be improved with an increase in niobium content due to the refinement of the graphite and pearlite interlamellar spacing. In this paper, adding less than 0.32% of Nb to grey cast iron is recommended, considering the comprehensive cost and the effect of niobium in the material structure.