Effect of aluminizing and oxidation treatment on microstructure and mechanical properties of CLAM steel

doi:10.13251/j.issn.0254-6051.2022.01.032

Abstract

Abstract: The aluminide coating was prepared on the surface of CLAM steel substrate by a suitable aluminizing and oxidation, then the microstructure and mechanical properties, especially the phase composition changes of the coatings before and after aluminizing and oxidation treatment were studied by means of XRD, EPMA, SEM, nanoindenter and room temperature tensile testing machine, as well the hardness changes and fracture mechanism of tensile fracture were analyzed in detail. The results show that after aluminizing and oxidation treatment, an aluminide coating composing of a 30.8 μm thick layer of FeAl phase and a 70.7 μm thick layer of α-Fe(Al) solid solution is formed on the surface of the CLAM steel. The hardness of the coating is up to 834.7 HV for the outermost FeAl phase, and gradually decreases to 315.1 HV from the outside to the inside, while the hardness inside the steel substrate rises slightly. The tensile strength of CLAM steel before and after aluminizing and oxidation is 581.38 MPa and 555.83 MPa, respectively, and the elongation after fracture is 30% and 28%, respectively. The fracture mode is changed from ductile fracture before aluminizing and oxidation to quasi-cleavage fracture. After aluminizing and oxidation, the tensile property of the CLAM steel is degraded and the crack sources are prone to be generated at the surface coating to accelerate the material fracture, which is due to the grain size increasing and the secondary phase particle aggregation caused by the aluminizing and oxidation treatment.

Key words: CLAM steel, aluminizing and oxidation, microstructure, nanoindentation, fracture analysis

CLC Number:

TG156.8

Zhao Xiaojun, Liang Xiao, Cai Zhenyang, Xiao Lairong. Effect of aluminizing and oxidation treatment on microstructure and mechanical properties of CLAM steel[J]. Heat Treatment of Metals, 2022, 47(1): 192-196.

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