Enhancement of shape and surface layer properties by laser direct deposition
Abstract
Laser direct deposition provides an attractive and cost effective means for enhancing or remanufacturing high value engineering components. This study demonstrates the successful repair of defective voids in turbine airfoils based on a new semi-automated geometric reconstruction algorithm and a laser direct deposition process. A Boolean difference between the original defective model and the final reconstructed model yields a parameterized geometric representation of the repair volume. The experimental results of this method demonstrate the effectiveness of laser direct deposition in remanufacturing and its potential to adapt to a wide range of part defects. A Life Cycle Assessment (LCA) on the energy and environmental impacts by remanufacturing is also presented. Functionally graded material improves components performance over the original parts. Functionally gradient material (FGM) can be tailored to the structural requirements of the final product. In this study, titanium carbide (TiC) reinforcement particles were embedded in Inconel 690 with laser direct deposition to build functionally gradient metal matrix composites (FGMMCs). The microstructures of the MMC and distribution of TiC particles were characterized with an optical microscope, SEM and X-ray diffraction. There was a near absence of internal voids in the deposited TiC-Inconel 690 MMC. With the volume percentage of TiC particles in the depositions varied from 0 to 49%, a drastic evolution in the microstructure was observed and the presence of TiC particles over 30% yielded a refinement of the matrix microstructure and introduction of a finely dispersed crystalline phase. High-temperature dissolution of TiC was not detected under the conditions used. Micro-hardness and wear resistance tests showed a significant improvement with increased TiC content. Functionally gradient bio -coating material was built by laser deposition. Co-Cr-Mo material was deposited on a Ti-6Al-4V substrate transitioning from 0 to 100%. Control over the cooling rate is shown to be a key to reduce the effects of thermal expansion differences of the materials. The microstructures and composition of the functionally gradient material (FGM) were characterized using an optical microscope, SEM, EDS and XRD. EDS results showed a gradual transition to 50% Co-Cr-Mo and ∼100% Co-Cr-Mo on the top layer. XRD analysis showed the absence of a brittle intermetallic phase that forms between Titanium and Cobalt. As the amount of Co-Cr-Mo increased, the microhardness of the FGM samples significantly increased. A comparison was made between Co-Cr-Mo deposited on SS316L substrates as well as Ti-6Al-4V. The bonding strength of the coatings on both substrates was tested and found to meet the ASTM standard requirement.
Degree
M.S.M.E.
Advisors
Shin, Purdue University.
Subject Area
Mechanical engineering
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