Effect of sintering densification on micro-scale mechanical and tribological behaviour of niobium carbide

The design of powder metallurgy components made of advanced ceramic materials demands information on mechanical behaviour, which affects lifetime, wear and friction performances. In sintered materials, microstructure plays a significant role in the final properties and is directly dependent on sintering cycle variables (temperature, pressure and time). Niobium carbide (NbC) presents high hardness and melting point, being a potential candidate to be used as bulk material and coating for industrial wear resistance applications. However, this carbide presents low sinterability and its hardness seems to be influenced by stoichiometry. Although the mechanical properties of NbC have been evaluated, few studies have been conducted to investigate the wear behaviour of NbC and even fewer considered the micro-scale level. In this work, experimental analyses of instrumented indentation and micro-wear were applied to evaluate a Spark Plasma Sintered (SPS) Niobium Carbide. The SPS sintering technique was used to achieve densification above those from traditional sintering techniques. Specific mechanical characteristics were obtained from load/displacement curves using instrumented indentation, while the wear behaviour was analysed using a micro-scale reciprocating test. Results showed that the relationship E/H seems to be the main factor governing tribological properties in this study. The wear and friction behaviours were also reproduced by numerical analysis, allowing further understanding on the effect of different features on the system performance.

Automated summary

The design of powder metallurgy components made of advanced ceramic materials requires information on mechanical behavior, which affects lifetime, wear, and friction performances. Sintered materials' microstructure depends on sintering cycle variables and plays a significant role in final properties. NbC has high hardness and melting point, but its sinterability and hardness may be influenced by stoichiometry. Experimental analyses showed that the relationship E/H is a key factor in governing tribological properties in this study, and wear and friction behaviors were reproduced by numerical analysis to understand the system performance.