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|Title: ||Formation of high chromium surface alloys on 2.25Cr-1Mo and 9Cr-1Mo steels using a single step laser treatment to improve their high temperature oxidation corrosion resistance|
|Authors: ||KHANNA, AS|
|Issue Date: ||1999|
|Publisher: ||MINERALS, METALS & MATERIALS SOC|
|Citation: ||ELEVATED TEMPERATURE COATINGS: SCIENCE AND TECHNOLOGY III,399-417|
|Abstract: ||Laser surface alloying (LSA) is becoming an important tool for modifying the surface composition of various relatively reactive substrates for enhancing their oxidation/corrosion resistance. In the present work, heat-exchanger materials, namely 2.25Cr-1Mo and 9Cr-1Mo steels were modified by a single-step LSA using a 3 kW CO(2) laser in continuous mode to achieve an increased chromium and nickel concentration at the surface. A 50% Ni + 50% Cr powder with particle size ranging between 22-45 mu m was fed simultaneously with a feed rate of 2 to 2.8 gm/min using a line focus mode with a spot size of 2 mm. Various samples were obtained by varying the sweep rate from 500 to 1000 mm/min. The surface morphology, composition and cross-section of the laser melted zone of LSA samples were analysed using optical microscopy, X-ray diffraction and SEM/EDAX. Various samples were subjected to oxidation tests at 800 degrees C in air and aqueous corrosion tests in 1N H(2)SO(4) and 3.5 % NaCl solutions, followed by the analysis of corrosion products. An attempt was made to compare the results on the surface composition, microstructure, corrosion and oxidation with the alloys with similar composition, made earlier using a two-step LSA.|
|Appears in Collections:||Proceedings papers|
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