Low-Temperature Fabrication of Refractory Thin Films via Electric Field and Contact Stress-Activated Sintering of Nanoparticles: An In Situ Study.

Refractory nanocomposite films are employed to prevent wear of mechanical components under harsh conditions; however, they are traditionally manufactured at elevated temperatures, causing undesirable microstructural transformations. This study presents a novel electric field- and contact stress-activated sintering process for fabricating tungsten carbide (WC-Co) films at low temperatures (100 °C). In this process, nanoparticle-containing "inks" are supplied to stressed sliding/rolling interfaces, while simultaneously applying direct current. Elevated stresses (>1 GPa) and electric currents (2-5 A) drive nanoparticle sintering on contacting surfaces, generating thin films within minutes. Here, we present the results of an in situ study of the kinetics of sintering using optical interferometry. The application of electric currents enhanced film thickness, reduced surface roughness, and increased the fraction of WC incorporated into the film. Co played a critical role in film nucleation by forming a deformable matrix for trapping hard WC nanoparticles. This manufacturing approach provides a rapid, low-temperature pathway for fabricating nanostructured films.