Morphology-Dependent Hardness of Cr 7 C 3 -Ni-Rich Alloy Composite vs Orientation Independent Hardness of Cr 7 C 3 Prima
- PDF / 1,555,190 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 56 Downloads / 197 Views
Chromium carbide-nickel-rich alloy composite coatings are used under erosive–corrosive conditions at high temperatures owing to their resistance to high wear, corrosion, and oxidation.[1] Laser cladding is one of the preferred methods to deposit such coatings.[2]
LAKSHMI NARAYANAN VENKATESH is with the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad, 500005, India, and also with the Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India. Contact e-mail: [email protected] PITCHUKA SURESH BABU and RAVI CHANDRA GUNDAKARAM are with the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI). ROGER D. DOHERTY is with the Department of Materials Engineering, Drexel University, Philadelphia PA 19104. SHRIKANT V. JOSHI is with University West, 461 86 Trollhattan, Sweden. INDRADEV SAMAJDAR is with the Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay. Manuscript submitted October 23, 2016. Article published online February 10, 2017 1534—VOLUME 48A, APRIL 2017
Microstructure and phase evolution besides composite hardness measurement have been the major components of studies on such coatings.[2–5] However, to our knowledge, our earlier report[5] is the only detailed study on this laser clad coating including precise phase identification, nature of solidification, carbide content quantification, stability of the carbide phase, and effect of carbide content and its secondary arm spacing on hardness. We found that although the starting powder contained Cr3C2 and Cr7C3, the final clad layer consists only of Cr7C3 which solidified dendritically with the nickel-rich metallic phase solidifying within the interdendritic phase. Each Cr7C3 dendrite is essentially a single crystal with a definite crystallographic orientation. Cr7C3 was found to be the primary as well as the stable carbide phase up to 1273 K (1000 C). Reference to this earlier work will be made wherever necessary. Electron backscattered diffraction (EBSD) measurement in a scanning electron microscope (SEM) across the clad cross section has been found to provide deeper insights into the microstructural aspects including crystallographic texture.[6] Laser cladding generally leads to a dendritic microstructure with columnar or equiaxed morphology depending on the local solidification conditions, which in turn depends on the process parameters.[7] Since heating is highly localized in laser cladding, considerable superheating and supercooling are expected. One of the aims of the present study is the study of the effect of superheating on the Cr7C3 grain structure using the EBSD technique. Microstructural aspects such as grain size, shape, and crystallographic orientation will be quantified and correlated with laser power. Cr7C3 has a hexagonal lattice structure, with lattice parameters a = 1.398 nm and c = 0.452 nm.[1] It is commonly known that hexagonal crystals are brittle
Data Loading...
