Title

Examination of Cr-Cr₃Si-NbC and Cr-(Cr,Mo)₃Si-NbC Alloys for Industrial Applications

Abstract

Refractory metal silicides have many desirable properties such as a high melting point, good corrosion resistance, low densities, and low wear rates. Previous investigators have produced Cr-Cr3Si-NbC alloys via a powder metallurgy route with Vickers hardness values ranging between 956 and 1338 and corrosion rates in boiling 70% sulfuric acid of 50 to 121 mpy. However, these alloys exhibit a fracture toughness of only 3 to 6.6 MPa-m-1/2. Other investigators demonstrated that the fracture toughness of the Cr-Cr3Si alloys can be improved to 8 MPa-m-1/2 with the addition of molybdenum. A series of Cr-Cr3Si-NbC and Cr-(CrMo)3Si-NbC alloys has been created in an attempt to improve on wear, corrosion resistance, hardness and fracture strength. These new alloy series will have NbC additions of 0, 5, 10 and 15-volume %. The alloys were also created via a powder metallurgy route. Elemental Cr, Mo, Si and NbC were mechanically alloyed and then hot pressed to produce the alloys. The base alloy for the Cr-Cr3Si-NbC series attained a toughness value of 3.5 MPa-m-1/2, while the base alloy for the Cr-(Cr,Mo)3Si-NbC series attained a value of 7.0 MPa-m-1/2. The hardness of the materials increased with increasing amounts of NbC and % theoretical density. The KIC for these alloys decreased only slightly. Molybdenum additions to the Cr-Cr3Si alloys seem to have increased the corrosion rates in 70% boiling sulfuric acid. The corrosion rates for the Mo-containing alloys has been shown to be reduced by additions of NbC > 10 vol.%. Cr-Cr3Si-NbC alloys had homogeneous microstructures consisting of a metal silicide, Cr-phase and NbC. The Cr-(CrMo)3Si alloys also had Cr and silicide phases, but there was a separation of the metal phase from (Cr,Mo) to Cr + Mo.

Meeting Name

Proceedings of a Symposia on Powder Metallurgy Alloys and Particulate Materials for Industrial Applications (2000: Oct. 8-12, St. Louis, MO)

Department(s)

Materials Science and Engineering

Keywords and Phrases

Addition Reactions; Corrosion Resistance; Fracture Toughness; Hot Pressing; Industrial Applications; Melting; Microstructure; Phase Composition; Powder Metallurgy; Sulfuric Acid; Vickers Hardness Testing; Wear of Materials; Chromium Molybdenum Silicon Carbide; Chromium Silicon Niobium Carbide; Refractory Metal Silicides; Vickers Hardness; Chromium Alloys

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2000 Minerals, Metals and Materials Society (TMS), All rights reserved.

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