Authors: James Sears, Aaron Costello
Abstract: Most materials produced today are monolithic structures that are heat treated to perform a
particular function. Laser Powder Deposition (LPD) is a technology capable of modifying a
metallic structure by adding the appropriate material to perform a desired function (e.g., wear and
corrosion resistance). LPD offers a unique fabrication technique that allows the use of soft (tough)
materials as base structures. Through LPD a hard material can be applied to the base material with
little thermal input (minimal dilution and heat-affected-zone {HAZ}), thus providing the function of
a heat treatment or other surface modifications (e.g., carburizing, nitriding, thermal spray and
electroplating). Several materials (e.g., Stellite 6 &21, 316 SS, 420 SS, M4, Rex 20, Rex 121, 10V,
AeroMet 100, CCW+, IN 625 and IN 718) have been deposited on to carbon steel (4140, 4340,
1566, 1018) substrates to provide various functions for a number of industrial applications. These
surface modifications have been evaluated through standard wear testing (ASTM G-65), surface
hardness (Rc), micro-hardness (vickers), and optical microscopy. The results from these
evaluations will be presented along with several industrial application case studies.
1537
Authors: Keisuke Uenishi, Yasuhito Ogata, Shingo Iwatani, Akira Adachi, Takehiko Sato, Kojiro F. Kobayashi
Abstract: For the improvement of a surface wear resistance of aluminum alloys, iron-based alloys
were clad on the surface of an aluminum alloy by laser. By investigating the effect of CO2 and
diode laser irradiation conditions on the formability of Fe-Cr-C clad layers, it was confirmed that
the application of diode laser made it possible to obtain stable beads in low heat input compared
with CO2 laser, which has been conventionally used for laser cladding. Besides, by optimizing the
laser parameters, the dilution ratio of clad layers by Al substrate was minimized less than 10%. At
the clad interface, the reaction layer consisting of Fe2Al5 and FeAl3 formed which caused cracks at
the clad interface. Even by controlling laser conditions, this brittle layer formation could not
suppressed. In this research, by using the immiscible Fe-Cu-Cr alloys as clad materials, Fe based
clad layers were formed on Al substrate without any cracks at clad interface. By the effect of
Marangoni motion of decomposed duplex liquid phases, Cu segregated between Al substrate and Fe
based clad layers and suppressed the reaction between them.
331
Authors: Xu Yue Wang, H.R. Guo, Yong Bo Wu, Wen Ji Xu, D.M. Guo
Abstract: Laser cladding of micro-fluidic channels mold was performed using Nd:YAG laser and synchronous powder feeder. Influences of laser power and powder feed rate on clad layer geometrical dimensions and qualities were investigated. Results show that powder feed rate 1.5-2.5 g/min used obtains micro clad layers which meet geometrical dimensions’ requirement of micro-fluidic channels mold and combination of parameters laser power 400 W and powder feed rate 2.0 g/min achieves micro clad layer with better clad quality. Scanning paths of micro-fluidic channels mold was planned through CAD-CAM software. Using optimum parameters combination, multilayer laser cladding experiment was carried out and a sample of micro-fluidic channels mold was fabricated with expectative structure and hardness. A little milling and polishing makes the sample meet technical requirements, 0.2mm in height and 0.3mm in width. Fabricating a mold takes 15-20 min totally.
424
Authors: Yong Qiang Guo, Hong Wei Zhao, Rong Lu Sun
Abstract: NiCrBSi coating was prepared on the surface of 45 steel by CO2 laser. The microstructure of the clad layer was characterized by SEM、EDS and XRD. The microhardness and wear resistance of the laser clad layer was examined. The results show that laser clad layer can be achieved under technical processing parameters and that the good metallurgical bonding is formed between the coating and substrate. The coating is uniform, continuous and free of pores and cracks. The microstructure of the coating is mainly composed of g-Ni, Ni3B, CrB and Cr23C6 particles. The microhardness of the coating (500～650HV0.2) is distinctly higher than that of the substrate(240～250 HV0.2). The clad layer is reinforced by particles and grain-refining, resulting in greatly increase in wear resistance comparing with 45 steel.
105
Authors: L. Venkatesh, Indradev Samajdar, Manish Tak, Ravi C. Gundakaram, S.V. Joshi
Abstract: Chromium carbide based metal matrix composite (MMC) coatings are ideally suited for high temperature erosive-corrosive applications. Laser cladding of such MMCs, with Inconel as the ductile matrix instead of the usual NiCr alloy, has been attempted in the present study. The relative hardness of the laser clad layers was observed to drop with increase in laser power. The reduction in hardness was attributed to retention of lower amounts of chromium carbides in the clad layer at higher laser powers. Use of chemically assisted scans with electron diffraction allowed extraction of effective micro-textural information on the coatings
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