Sreekar Karnati

Microstructure and properties of functionally graded materials Ti6Al4V/TiC fabricated by direct laser deposition

This paper aims to manufacture Ti6Al4V/TiC functionally graded material (FGM) by direct laser deposition (DLD) using Ti6Al4V and TiC powder. The objective is to investigate the effect of process parameters and TiC composition on microstructure, Vickers hardness and mechanical properties.,Powder blends with three different volume percentages of Ti6Al4V and TiC were used as feed material for DLD process. Five experiments with different values of laser power and scan speed were conducted to investigate the effect on microstructure and Vickers hardness for different compositions of feed material. Mini-tensile tests were performed to evaluate the mechanical properties of the FGM samples. Digital image correlation (DIC) was applied to estimate Young’s modulus and ultimate tensile stress (UTS) of heterogeneous material.,This paper indicates that primary carbide, eutectic carbide and un-melted carbide phases are formed in the FGM deposit. As the energy density was increased, the primary and secondary dendrite arm spacing was found to increase. As TiC composition was increased, Young’s modulus increased and UTS decreased. The dendritic morphology of primary TiC growth was expected to cause low resistance for crack propagation, causing lower UTS values. Tensile specimens cut in vertical orientation were observed to possess higher values of Young’s modulus in comparison with specimens cut horizontally at low carbon content.,Current work presents unique and original contributions from the study of miniature FGM tensile specimens using DIC method. It investigates the effect of specimen orientation and TiC content on Young’s modulus and UTS. The relationship between energy density and dendritic arm spacing was evaluated. The relationship between laser power and scan speed with microstructure and Vickers hardness was investigated.

Contrast of Repair Capabilities Between Laser Metal Deposition and TIG Welding on Ti-6Al-4V

Ti-6Al-4V is a popular aerospace alloy employed in various aerospace structures and their critical components. Irrespective of cause, a defect of few cubic millimeters in volume could declare the disposal of a component making it a costly affair. In the current effort, a hybrid approach of additive and subtractive processes was adopted to repair material removal and plastic deformation defects. Laser metal deposition and welding were the additive processes chosen for repair of the defects, and mini-tensile testing was employed as the characterization technique. A two-way statistical analysis was performed on the outputs obtained from the testing to establish the superiority in repair capability for each of the additive processes. The avg. yield strength obtained from laser repaired samples was found to be around 25% more than weld repaired specimens and avg. grain size for the laser repaired specimens was found to be approximately 1/3rd the size from weld repair.Copyright