Ta2C precipitation after low pressure carburizing of tantalum

Low pressure carburizing cycles were carried out on tantalum samples. A Ta2C precipitates layer is present under the TaC and Ta2C surface layers. As the TaC and Ta2C layers, the Ta2C precipitates layer (TPL) grows by carbon diffusion in tantalum matrix. Specific zones with low precipitates content were observed at the bulk surface and in the tantalum grain boundaries. Other zones with lower precipitates content are also present in carburized and annealed samples. All the zones with low precipitates content are induced by the Ta2C precipitation mechanism described by Dahmen et al. [1,2]. Indeed, Ta2C needs vacancies to precipitate. If vacancy sinks are present at the bulk surface, at a grain boundary or in a dislocation, then Ta2C precipitation is highly reduced. Another effect of the annealing treatment is an increase of the Ta2C precipitates layers growth rate. •This paper presents the first research work about Ta2C precipitates layer growth.•Tantalum matrix vacancies are consumed during the precipitation of Ta2C.•Ta2C precipitation is reduced close to vacancy sinks (grain boundary, surface, …).•Ta2C precipitation is also reduced in zones where Ta2C precipitates had appeared at least once.•An annealing treatment following a carburizing treatment increase the Ta2C precipitates layer growth.