Search

In this work, we traced structural transformations of an Al62.5Cu25Fe12.5 alloy, in which a quasicrystalline icosahedral phase (i-phase) can be formed, upon spraying onto a substrate and consolidation from the powder into the bulk state. The Al62.5Cu25Fe12.5 powder was obtained by gas atomization and consisted of i-phase and τ-phase AlCu(Fe). The powder was detonation sprayed (DS) and consolidated by spark plasma sintering (SPS)/hot pressing (HP). During DS, the particles experienced partial or complete melting and rapid solidification, which resulted in the formation of coatings of a complex structure. The composite regions containing i-phase were inherited from the powder alloy. The fraction of the material that experienced melting solidified as β-phase AlFe(Cu) in the coating. It was suggested that the difficulty of obtaining i-phase upon post-spray annealing is related to aluminum depletion of the alloy during DS. During SPS and HP, the elemental composition of the alloy was preserved, while the exposure to an elevated temperature led to phase homogenization. SPS and HP conducted at 700ºC resulted in full densification and the formation of a single-phase quasicrystalline alloy. The sintered single-phase alloy showed a higher microhardness in comparison with the DS coatings.

Al2O3 particle-modified Fe66Cr10Nb5B19 metallic glass matrix coatings were deposited on carbon steel substrates by detonation spraying of the corresponding powder mixtures. The microstructure, mechanical and tribological properties of the coatings were investigated. In the microstructure of the coatings, the Al2O3 particles were located between the layers of the Fe66Cr10Nb5B19 amorphous alloy. The bonding strength between the substrate and composite coatings was ~ 130 MPa. The wear behavior of the coatings was studied under dry linearly reciprocating conditions in a ball-on-flat mode using a WC-6Co ball as a counterbody. It was found that the friction coefficients of the Al2O3-free coating and composite coatings were close to each other and varied in the range of 0.64–0.70. The specific wear rate of the coatings modified with 1.5 and 4 vol.% of Al2O3 was 2.5 × 10−5 and 3.1 × 10−5 mm3 N−1 m−1, respectively, which is about one-fifth of the specific wear rate of stainless steel. It was suggested that the dominating wear mechanisms of the Fe66Cr10Nb5B19-Al2O3 composite coatings are fatigue and abrasion wear. [ABSTRACT FROM AUTHOR]

Detonation spraying of wear-resistant Cr3C2-NiCr coatings was carried out using a two-fuel 0.61C2H2 + 0.26C3H8 + O2 explosive mixture. The coatings were formed from agglomerated powders containing 10, 20 and 25 wt.% of the nichrome binder. The deposition efficiency was measured. The microstructure, bonding strength, hardness and wear resistance of the coatings were studied as functions of the spraying distance and spraying angle. The coatings of the highest quality had a porosity of less than 0.5%. Irrespective of the binder content, the bonding strength of the coatings was equal to or greater than 150 MPa. In the ASTM G-65 abrasion test, the volume loss of Cr3C2-20NiCr coating was 3.1 mm3/1000 rev. In addition, the level of residual stress was evaluated using the Almen test. The coatings of the highest quality possessed compressive residual stresses. For applications under wear conditions and increased mechanical loads, a coating containing 20% of NiCr binder is recommended. The results of this study can be useful for selecting the modes of the coating deposition on components of complex shape. [ABSTRACT FROM AUTHOR]

In the present work, Fe66Cr10Nb5B19 metallic glass coatings deposited by detonation spraying (DS) on carbon steel substrates were structurally characterized and tested in 3.5 wt.% NaCl solutions with pH values of 3.0, 5.5, and 10.0 under potentiodynamic polarization conditions. The coatings had low porosity (2.9-4.5%) and showed a predominantly amorphous structure. The concentration of an amorphous phase in the detonation coatings was 97.5-99.5 wt.%. Such high concentrations were not observed in thermally sprayed Fe-Cr-Nb-B coatings obtained by other research groups. Under the test conditions, the coatings exhibited low corrosion current densities (of the order of 10-6 A cm-2) and low passive current densities (below 10-3 A cm-2) while showing extended passive regions (stable within 1.5 V from the corrosion potential). The Fe66Cr10Nb5B19 coatings produced by DS showed a much better corrosion resistance than the carbon steel substrate. Furthermore, the corrosion resistance of the Fe66Cr10Nb5B19 DS coatings was superior to that of flame-sprayed or high-velocity oxygen fuel-sprayed Fe-Cr-Nb-B coatings reported to date. These results open new prospects for the use of affordable and Cr-lean Fe-Cr-Nb-B glassy coatings for carbon steel protection, where chloride-induced corrosion is the major degradation risk, such as metallic components for marine applications. [ABSTRACT FROM AUTHOR]

Copyright of Science of Sintering is the property of National Library of Serbia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)