| Abstract: |
Ni-Al intermetallic alloys are known for exhibiting superior high temperature properties. Processes such as thermal spray, combustion synthesis, physical vapor deposition and laser have been used to produce these coatings. However, the deposition of these alloys by plasma transferred arc (PTA) hardfacing has not been widely studied. This study analyzed Ni-Al coatings processed in-situ by PTA. Coatings were processed with Ni and Al elemental powders (80%wtNi 20%wt Al) onto an AISI 1020 steel substrate. This steel was selected to minimize the diversity of alloying elements diffusing from the substrate. Different deposition current were used (70 to 120 A) to produce different dilution levels and thus different Fe content in the coatings. The stand torch off was 10.0 mm. The plasma gas, shield gas and powder carrier gas flows were 2.0, 15.0 and 0.8L.min-1, respectively. The powder feed rate was 5.8g.min-1 and the travel speed of 100 mm. min-1 was used. The coatings were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, optical microscopy and instrument indentation tests. The development of Ni aluminides was confirmed by X-ray diffraction for all the deposition current. It was observed that the microstructure, hardness and the elastic modulus were influenced by the deposition current and therefore by the Fe content in the coating.
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