Oxidation resistance of borided pure cobalt

Plasma boriding of a cobalt–chromium alloy as an interlayer for nanostructured diamond growth

“…While metal-boride interaction for other high temperature boron diffusion methods has been investigated [12,[14][15][16], we find that microwave plasma CVD boriding leads to the formation of additional boride compounds. In addition to body-centered tetragonal Co 2 B and orthorhombic CoB phases observed from powder-pack bording studies [4,15], XRD also revealed orthorhombic CrB (O), body-centered tetragonal CrB (T), and rhombohedral MoB. In Figure 1b, a narrower 2 scale is shown from 40-50 degrees to enhance scan detail where FCC Co (111) would be observed (dashed red line).…”

“…These approaches often involve an extra processing step beyond CVD and have yielded limited success. Boriding results in a much higher hardness and higher resistance to wear, oxidation, and corrosion compared to other conventional thermo-chemical surface modification methods like carburizing and nitriding [12][13][14][15]. While boriding of steels (primarily using powder packing or molten salt methods) is widely reported, research on cobalt borides has become more active only in the past decade because of their catalytic and magnetic properties [4,16,17].…”

Boriding kinetics of pure cobalt

“…Mu et al [16] observed that Co 2 B, Co 2 B+Co 2 Si and Co 2 Si phases form on the surface of borided with commercial LSBII powders (that contain SiC) for pure Co samples borided for 8 h at 1123, 1173 and 1223 K, respectively. From the same study, X-ray peaks for the borides could not be observed when pure Co was borided at 1223 K for 8 h due to the silicide phase covering the boride layer.…”

“…It has been successfully applied to various ferrous and nonferrous metals. Pack boriding of transition metals has shown limited success; in some metals (e.g., nickel) the presence of SiC and KBF 4 in the boriding powder results in the formation of silicides and borosilicides which generally have a negative influence on the hardness of the *Corresponding author: e-mail address: nazmucar@yahoo.com boride layer [12][13][14][15][16]. In the present study, pure cobalt was borided using the powder pack method using commercial Ekabor III powders containing SiC and KBF 4 .…”

Oxidation stability of boride coatings

“…During this process, temperatures of 973-1273 K and processing times of 1-10 h are typically used [1][2][3]. Since boron is a relatively small size element, it easily diffuses into a variety of metals, including Fe and Co-based alloys and refractory materials [4][5][6][7][8]. The resulting boride layers are characterized by high hardness, good wear, heat and corrosion resistance.…”