Microstructural characterization and in situ transmission electron microscopy analysis of laser-processed and thermally treated Fe-Cr-W-C clad coatings

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02646601· OSTI ID:6240434

Nagarathnam, K; Komvopoulos, K ^[1]

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1. Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering

Rapidly solidified microstructures of Fe-Cr-W-C quaternary alloy deposited on low-carbon steel by laser cladding were investigated. The clad-coating alloy, a powder mixture of Fe, Cr, W, and C with a weight ratio of 10:5:1:1, was processed with a high-power continuous wave CO[sub 2] laser. The laser processed microstructure comprised fine primary dendrites of a face-centered cubic (fcc) austenitic [gamma] phase and interdendritic eutectic consisting of a network of pseudohexagonal M[sub 7]C[sub 3] carbides rich in Cr in an fcc austenitic [gamma] phase. The interlamellar spacing in the eutectic matrix was about 20 nm. The relatively high microhardness, about 900 kg[sub f]/mm[sup 2], of such fine microstructures is attributed to the formation of complex ternary carbides uniformly distributed in the eutectic matrix. In situ transmission electron microscopy (TEM) of thermally treated clad coatings revealed that transformation of the primary [gamma] phase to body-centered cubic (bcc) ferrite ([alpha] phase) commenced after heating at 843 K for about 7 minutes. Phase change of the interdendritic [gamma] austenite to a bcc [alpha] ferrite occurred after about 30 minutes of hold period at 843 K. Transformation of the M[sub 7]C[sub 3] carbides did not occur even after heating at 843 K for about 3.2 hours. The growth of a thin M[sub 2]O[sub 3] (M = Fe, Cr) oxide scale was detected after heating at 843 K for approximately 24 minutes. After cooling gradually to room temperature, the softened (723 kg[sub f]/mm[sup 2]) microstructure consisted of primary dendrites with a bcc [alpha] ferrite crystal structure and interdendritic ternary eutectic of untransformed M[sub 7]C[sub 3] carbides in [alpha] ferrite.

• OSTI ID: 6240434
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 24:7; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM ALLOYS
MICROSTRUCTURE
IRON BASE ALLOYS
AUSTENITE
CARBIDES
CARBON ADDITIONS
COATINGS
CRYSTAL-PHASE TRANSFORMATIONS
EXPERIMENTAL DATA
FERRITE
HEAT TREATMENTS
LASER RADIATION
MICROHARDNESS
PHASE STUDIES
STEELS
TRANSMISSION ELECTRON MICROSCOPY
TUNGSTEN ADDITIONS
X-RAY SPECTROSCOPY
ALLOYS
CARBON COMPOUNDS
DATA
ELECTROMAGNETIC RADIATION
ELECTRON MICROSCOPY
HARDNESS
INFORMATION
IRON ALLOYS
MECHANICAL PROPERTIES
MICROSCOPY
NUMERICAL DATA
PHASE TRANSFORMATIONS
RADIATIONS
SPECTROSCOPY
TUNGSTEN ALLOYS
360102* - Metals & Alloys- Structure & Phase Studies