Structure and Properties a TiB2–Ag Coating Deposited by Electroexplosive Spraying on Copper

TiB2–Ag coatings are deposited by electroexplosive spraying on a copper surface for the first time. The idea of creating such coatings is based on the high properties of the initial materials used to form the coatings, namely, titanium diboride and silver. Silver is used to create a matrix with a high electrical conductivity, and titanium diboride, in turn, serves as a wear-resistant, hard, electroerosion-resistant filler for the matrix. Moreover, titanium diboride has a high electrical conductivity among other similar fillers, such as tungsten and molybdenum. The essence of the work is that TiB2–Ag coatings are deposited onto a copper target–substrate by electroexplosive spraying. Electroexplosive spraying is carried out using a silver foil and a titanium diboride powder under the conditions that ensure melting of the copper target–substrate. The deposited coatings are intended for use in electrical contact switching devices. Therefore, we study the following minimum basic properties necessary for the stable operation of electrical contacts in switching devices: microhardness, nanohardness, Young’s modulus, wear coefficient, friction coefficient, electrical conductivity, and switching wear resistance. The following main results have been obtained. The electrical conductivity of the TiB2–Ag coating is 62.0 MS/m. The coating withstands 7000 switching cycles during accelerated electroerosion resistance tests. The electrical resistance does not exceed 12.82 μΩ. The Vickers microhardness in the silver matrix of the coating is 0.251–0.265 GPa, and that at titanium diboride inclusions is 25–32 GPa. The nanohardness is H = 4.48 ± 0.76 GPa and Young’s modulus is E = 116 ± 29 GPa. Under dry sliding friction conditions, the wear parameter is 1.2 mm3/(N m) and the friction coefficient is 0.5. X-ray diffraction analysis demonstrates that the coating contains silver (a = 4.0779 Å, CSR = 42) and titanium diboride (a = 3.0535 Å, c = 3.2618 Å, CSR = 38). Scanning electron microscopy demonstrates that the coating 100–110 μm thick has a composite filled structure, which consists of a silver matrix with titanium diboride inclusions 1–20 μm in size. Transmission electron microscopy demonstrates that the main phase of the coating is silver or an Ag + Cu solid solution reinforced with titanium diboride nanoparticles.