Defence Metallurgical Research Laboratory

About: Defence Metallurgical Research Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 1208 authors who have published 2662 publications receiving 51663 citations.

High temperature low cycle fatigue deformation behaviour of forged IN 718 superalloy turbine disc

Abstract: In the present investigation, low cycle fatigue deformation behaviour of forged turbine disc of IN 718 superalloy of different sections (rim, hub, and bore) was studied under asymmetrical waveforms (slow–fast and fast–slow) at 650 °C. The superalloy exhibited dynamic strain aging (DSA) by showing the manifestation of serrations during the lower strain rate plastic region of the hysteresis loop under asymmetrical waveforms. Irrespective of different sections, the superalloy showed marginally reduced fatigue life under slow–fast waveform as compared to fast–slow waveform. This was attributed to higher accumulation of LCF damage under slow–fast waveform as confirmed from slip band spacing than that of the fast–slow waveform.

Thermal barrier coatings from sol-gel-derived spray-grade Y2O3-ZrO2 microspheres

Abstract: For the development of ceramic thermal barrier coatings, spray-grade yttria-stabilized zirconia microspheres were prepared by the sol-gel technique. Oxide microspheres were obtained by calcination of the corresponding gel spheres at 1000 °C. Scanning electron microscopic and optical microscopic observations revealed the material thus obtained to have a predominantly spherical morphology and the requisite size distribution (5–50 μm). The dense, calcined microspheres showed good flowability. X-ray diffraction studies indicated the presence of the tetragonal polymorph of ZrO2 as the major phase, in addition to about 14% monoclinic ZrO2. The plasma-sprayed YSZ coatings made from the sol-gel-derived microspheres showed a further decrease in the monoclinic ZrO2 content (6%). The coatings survived 40–50 thermal cycles (30 min at 1200 °C followed by a water quench), indicating good thermal shock resistance.

Superior energy storage performance and fatigue resistance in ferroelectric BCZT thin films grown in an oxygen-rich atmosphere

Abstract: Ferroelectric properties of chemical-solution-deposited Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCZT) thin films in the 200 nm thickness range, grown in air and oxygen-rich atmospheres, were investigated. Oxygen-processed BCZT thin films were found to have very slim hysteresis with higher polarization, lower remanent polarization (Pr), much lower coercivity and much higher dielectric breakdown strength. Those properties resulted in superior energy storage properties. Oxygen-processed BCZT thin films showed an energy storage density (ESD) of 64.8 J cm−3 and energy storage efficiency (ESF) of 73% at 2000 kV cm−1 electric field. Apart from that, the films showed very low leakage current and improved polarization fatigue properties. Oxygen-processed virgin BCZT film displayed maximum polarization (Pmax) of 106 μC cm−2 and Pr of 12.9 μC cm−2, whereas the measured Pmax and Pr of the fatigued film after 1010 switching cycles were 105 μC cm−2 and 13.2 μC cm−2 respectively. BCZT thin films with high ESD and ESF at 2000 kV cm−1 electric field and with excellent fatigue properties could be considered as potential candidates for low and intermediate voltage ferroelectric energy storage applications.