Structural Characteristics and Their Influence on the Properties of Transition Metal Nitride and Boride Films (Overview)

Ultrahigh-temperature ceramics (UHTC) have a wide range of applications, particularly in supersonic aircraft vehicles. However, the production of UHTCs with predetermined mechanical parameters is relevant. The paper analyzes the structurization trends and their influence on the properties of film coatings from transition metal nitrides and borides synthesized by ion-plasma and magnetron sputtering methods. Under optimal deposition energy conditions, the films show general regularities in their formation, such as the presence of a columnar (fibrous) structure and growth texture. The average grain size varies from 18–20 nm to 60–80 nm, depending on the deposition parameters and method. The films demonstrate excellent mechanical properties, including hardness, elastic modulus, recoverable elastic indicators under load, etc. Growth directions <111> and <100> are observed for transition metal carbide and nitride coatings, while growth in direction <0001> is typical of transition metal diborides. The identified trends will allow realistic computer modeling of the film formation process, using predetermined film properties and optimal sputtering parameters to promote excellent mechanical characteristics of the surface. A thermodynamic model describing the formation of nuclei for a typical film in the environment of atoms randomly deposited onto the substrate is proposed. The critical radius for nucleus growth and, accordingly, for film crystallization is analytically estimated. The influence of Gibbs energy changes on the crystallization process is discussed within the model.