IN625 Ni-based metal matrix composites (MMCs) components were deposited using Laser Engineered Net-Shaping (LENS) with Ni-coated and uncoated TiC reinforcement particles to provide insight into the influence of interfaces on MMCs. The microstructures and spatial distribution of TiC particles in the deposited MMCs were characterized, and the mechanical responses were investigated. The results demonstrate that the flowability of the mixed powders, the integrity of the interface between the matrix and the TiC particles, the interaction between the laser beam and the TiC ceramic particles, and the mechanical properties of the LENS-deposited MMCs were all effectively improved by using Ni-coated TiC particles. DOI: 10.1007/s11661-009-0126-5 Ó The Author(s) 2010. This article is published with open access at Springerlink.com Particle-reinforced metallic matrix composites (MMCs) are of interest in many applications due to their multifunctionality, which yields combinations of properties, such as high specific strength, stiffness, and toughness, and a low coefficient of thermal expansion, that are unachievable with conventional materials. [1] Ni-based MMCs with ceramic reinforcements are used in a wide range of industrial operations with cutting, rolling, pelletizing, stamping, piercing, drawing, punching, etc.[2] Various synthesis methods, including casting and powder metallurgy techniques, have been used for conventional manufacturing of MMCs. [3,4] The presence of undesirable interfacial reactions and particle segregation represents two key issues that have limited the use of casting methods, partially due to an extended contact time between ceramic particles and the molten metal and density differences between ceramic and metals. In contrast, whereas conventional powder metallurgical routes avoid the presence of a liquid phase, these are relatively complex processes frequently limited in terms of product geometry. The LENS* process, incorporating features from stereolithography and laser cladding, is a laser-assisted direct metal manufacturing process that provides a pathway to produce net-shaped components from a three-dimensional (3-D) computeraided design file.[5] The primary advantages associated with LENS are the following: a small heat affected zone with high cooling rate resulting in fine microstructures; easy gradient deposition of multiple materials within a single component; and fully dense near-net-shape metal components. However, only spherical powders with diameters of 36 to 150 lm are recommended for use in LENS processing.[6] Thus, optimization of the LENS requires fundamental study of the influence of fine and irregular shaped ceramics particles in the case of MMCs.The strength and stability of the interfacial region between the reinforcement particles and metal matrix govern the mechanical properties of MMCs, and extensive efforts have been devoted to understanding and manipulating the interfacial behavior in MMCs. In the case of metal-ceramic MMCs, it is often desirable to promote wettability while ...

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High Mo surface alloys on stainless steels 304L and 316L were produced by laser surface alloying. For this, a layer of 60 pm thickness was overlaid on the substrates by plasma spraying of Mo powders. These were further treated by a Nd:YAG pulsed laser for alloying. Depths of alloying in the range of 440-1110 mm were achieved. Concentration in the range of 5.2-15.0 wt% Mo within the laser alloyed zone was, in general, uniform throughout. During alloying, in-situ heating at 700°C was required to prevent cracking in samples with 5.2-6.0 wt% Mo. Higher Mo content enhanced the cracking tendency and made it difficult to prevent cracking completely even at this temperature. Fully austenitic microstructure of the substrate metals transformed to austennitic-ferritic duplex for 5.2-9.0 wt% Mo and to fully ferritic for 15.0 wt% Mo. Primary solidification mode also changed to FA, FA + F and finally to F depending upon Mo content in the alloyed zone. Ferrite content in the alloyed zone was in the range of 31-79% depending upon amount of Mo. Microhardness was increased from 173 VHN for 316L to 198-790 VHN depending upon wt% Mo in the alloyed zone. Preliminary studies indicated that pitting potential in 3.5% NaCl aqueous solution improved substantially from 132 mV for 304L and 240 mV for 316L to 480 mV and 500 mV respectively for 5.5-6.0 wt% Mo in the alloyed zone.

This report was prepared by the Powdermet Inc, Euclid, Ohio for the DOE I&I proposal Category 2 entitled "Oxide Dispersion Strengthened Iron Aluminide by CVD coated Powders" Award Number DE-FG36-03GO13012. Fabrication and Evaluation of the Mechanical and Physical Properties of Iron Aluminide composites and its thermal sprayed coatings using chemical vapor deposition (CVD) aluminum, iron and aluminum oxide coated iron powders and iron, aluminum coated aluminum oxide powders were evaluated as part of a DOE I & I Category 2 Program following the successful completion of a preceding SBIR Phase-I assignment on the same subject. The objective of this program was to develop and optimize CVD aluminum, iron and aluminum oxide coated iron powders and iron, aluminum coated aluminum oxide powders for thermal spray application and optimize the fabrication of this Iron Aluminide composites, and it's coatings and evaluate the performances of these new materials for potential use as high temperature, oxidation, corrosion and carburization resistant material aimed for future power generation and boiler equipment. The program developed CVD coated powders demonstrated the fabrication of oxide dispersion strengthened (ODS) Fe 3 Al composites with a tensile value of 121 KSI and oxidation, carburization and corrosion resistant thermal sprayed coating The Prime Contract manager was Mr.