Structure and tribological behavior of Ni-B and Co-B galvanic coatings

Structural state and tribological properties of Co-P coatings

“…With an increase in the phosphorus concentration in the Co-P coating to 10,12,15, and 20 at %, two diffuse lines (Figs. 5b, 5c, 5d) appear in their XRD patterns that are typical of diffraction from amorphous materials [11].…”

“…2) and ensures a high hardness of the coating. With a fur ther increase in the concentration of phosphorus in the coating to [P] ≥ 8 at %, a combined amorphous crystalline structure is formed at 8 at % P and an amor phous structure appears at 10,12,15, and 20 at % P. In our opinion, the formation of the amorphous crystal line structure of the Со 92 Р 8 coating may be due to the alternating depletion of and enrichment of the near cathode layer in the phosphorus ions, which leads to the production of a coating that consists of alternating layers with crystalline (a decreased concentration of phospho rus) and amorphous (an increased concentration of phosphorus) structures. Another possible mechanism of the formation of the amorphous crystalline structure is the displacement of the phosphorus atoms into the near boundary regions adjacent to the α Со crystals that grow during electrocrystallization, which results in the appear ance of amorphous phosphorus enriched interlayers between the α Со crystallites.…”

“…Thus, it can be concluded that, during dry friction, the crystallization of the coatings with the amorphous structure occurs. The results of the tribotests can be explained based on the model of the wear of amorphous materials and coat ings under dry friction proposed in [15,16]. According to [15,16], during friction, severe deformation and heating of the surface layers of the coating occurs, which results in the crystallization of the amorphous structure and in the formation of thin surface layers with a crystalline structure.…”

“…The results of the tribotests can be explained based on the model of the wear of amorphous materials and coat ings under dry friction proposed in [15,16]. According to [15,16], during friction, severe deformation and heating of the surface layers of the coating occurs, which results in the crystallization of the amorphous structure and in the formation of thin surface layers with a crystalline structure. Since the crystalline zones of the coating have a substantially smaller specific atomic volume than the amorphous matrix, the crys tallized volumes of the material of the coating undergo high tensile stresses [15,16].…”

Optimization of Wear Performance of Electroless Ni-B Coating under Lubrication

“…Due to its excellent mechanical, electrical, physical, corrosion, hardness, friction and wear resistance properties [3], it has a wide range of industrial applications. It is also noted that Ni-B coatings have high hardness and superior wear resistance characteristics [4][5][6][7][8]. It may be applied on irregular and intricate shapes of geometries due to its smooth and uniform deposition over the substrate.…”