Corrosion behaviour of crystalline and amorphous forms of the glass forming alloy Fe43Cr16Mo16C15B10

• Published in: Journal of alloys and compounds Vol. 527; pp. 210 - 218
• Main Authors: Bakare, M.S., Voisey, K.T., Chokethawai, K., McCartney, D.G.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.06.2012; Elsevier
• Subjects: Amorphous materials; Applied sciences; Corrosion; Corrosion mechanisms; Crystal structure; Current density; Exact sciences and technology; Ferrous alloys; Flame spraying; Forming; Glass; HVOF coating; Laser melting; Lasers; Metallic glasses; Metals. Metallurgy; Microstructure; HVOF coating; Metallic glasses; Corrosion; Microstructure; Laser melting; Surface morphology; HVOF spraying; Cracking; X ray diffraction; Glass formation; Corrosion resistance; Potentiodynamic method; Transition metal alloy; Laser fusion; Iron base alloys
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.02.127

► A Fe-based GFA is made, comprising two M23C6 phases, Mo2FeB2, M3Mo3C and some (-Fe. ► The largely amorphous form of the alloy has superior corrosion resistance to the crystalline form. ► The crystalline form corrodes by preferential dissolution of Mo-rich precipitates. ► The improved corrosion behaviour is due to the homogeneity of the largely amorphous alloy. ► Conversion of the crystalline form to a largely amorphous form by laser melting. ► The use of laser melting to amorphise the alloy is limited by induced cracking. ► HVOF can deposit coatings that largely retain the amorphous structure. ► HVOF microstructural details effect corrosion performance of the amorphous form. The corrosion behaviour of both crystalline and largely amorphous forms of the Fe-based glass forming alloy, Fe43Cr16Mo16C15B10 alloy was investigated. Two different methods were used to induce transformation to the amorphous form of the alloy: laser melting and HVOF spraying. Both methods produced largely amorphous material, however the high brittleness of the alloy makes it susceptible to cracking during laser treatment, hence this technique is not suitable for large-scale application. Potentiodynamic scanning showed that in 0.5M H2SO4 and 3.5% NaCl electrolytes both amorphous forms of the alloy had better corrosion resistance (lower current densities for −200 to +1000mV SCE) compared to the crystalline material. The laser treated material and HVOF coating performed similarly in 3.5% NaCl. In 0.5M H2SO4 the HVOF coating had a lower current density than the laser melted material for almost all of the potential range −300 to +1000mV SCE. The improved corrosion behaviour of the largely amorphous material is attributed to its homogeneity, and particularly to the elimination of the Mo-rich phase that underwent preferential corrosion in the crystalline form of the material.