Synthesis And Properties Of New Fe-based Bulk Metallic Glasses With High Corrosion Resistance

Bulk metallic glasses (BMGs) have attracted considerable attention because of their unique properties and great potential for pratical applications. Although the Ni-based metallic glass coatings on bipolar plate worked in proton exchange membrane fuel cells exhibit good performance, the high cost limits its commercial application. The Fe-based BMGs with good properties and low cost are considered to be extremely viable candidates as new type anti-corrosion coatings. Nevertheless, the developed Fe-based BMGs do not simultaneously possess low glass transition temperature (Tg), wide supercooled liquid region (△TX), high glass forming ability (GFA) and excellent corrosion resistance, which are not suitable for HVOF spray-coating processing. In this work, with the aim of developing new Fe-based BMGs suitable for bipolar plates, we investigated the effects of some corrosion-resistance elements such as Cr, Mo, and Ni on the thermal stability, GFA and corrosion resistance of a Fe-based Fe80P12C4B4metallic glass with low Tg.The main research results are as follows:1. The stability of supercooled liquid and GFA of the Fe-P-C-B metallic glass are significantly enhanced by addition of Cr and Mo. The △Tx of Fe-P-C-B metallic glass increases from 29 K to 49 K, and the critical diameter for glass formation (dc) also enhances to 1.5 mm.2. Substitution of Ni for a portion of Fe in the Fe-Cr-Mo-P-C-B metallic glasses not only increases the △Tx and GFA, but also decreases the Tg. The Fe5oNi15Cr7Mo3P12C4B4BMG possesses the largest dc of 2.5 mm, combined with low Tg of 690 K and wide △Tx of 60 K,.3. Addition of Cr, Mo and Ni in the Fe80P12C4B4 alloy also improves the corrosion resistance. Electrochemical erosion and weight-loss tests show that the (Fe, Ni)-(Mo, Cr)-P-C-B BMGs exhibit excellent corrosion resistance in 1 N H2SO24 and 3% NaCl solutions; Especially, they have superior corrosion resistance to SUS316L stainless steel in 1 N HCl.4. The corrosion behavior of pre-annealed Fe55Ni15Cr7Mo3P12CB4 metallic glass was investigated. Although the corrosion resistance of alloy in 1 N H2SO4 solution reduces slightly due to the partial crystallinzation, it is still comparable to SUS316L.5. The (Fe, Ni)-(Mo, Cr)-P-C-B BMGs possess good mechanical properties with high yield strength of 2790-3420 MPa, and plastic strain of ～1.2%. The developed (Fe, Ni)-(Cr, Mo)-P-C-B BMGs simultaniously possess low Tg, wide △Tx, high GFA, superior corrosion resistance, and good mechanical properties, which makes them excellent prospects as bipolar plate surface coating for proton exchange membrane fuel cells.