Refractory oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated to near theoretical density using high voltage electric discharge compaction. Cylindrical samples with relative density from 90% to 97% and dimensions of 10 mm in diameter and 10–15 mm in height were obtained. Consolidation conditions such as pressure and voltage were varied in some ranges to determine the optimal compaction regime. Three different concentrations of yttria were used to identify its effect on the properties of the samples. It is shown that the utilized ultra-rapid consolidation process in combination with high transmitted energy allows obtaining high density compacts, retaining the initial structure with minimal grain growth. The experimental results indicate some heterogeneity of the structure which may occur in the external layers of the tested samples due to various thermal and electromagnetic in-processing effects. The choice of the optimal parameters of the consolidation enables obtaining samples of acceptable quality.
Oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated using high voltage discharge compaction to near theoretical density. Such rapid process in combination with high transmitted energy allows obtaining high density of the compacts, saving initial structure with minimal grain growth. Heterogeneity of the structure may occur in the boundary layers of the sample due to thermal and electromagnetic effects but the choice of optimal parameters of consolidation allows obtaining samples of acceptable quality.
The outcomes of the mechanical alloying of 13Cr-2Mo ferritic/martensitic steel and yttria (oxide-dispersion-strengthened steel) powders in a ball mill are reported in terms of the powder particle size and morphology evolution. The optimal ball mill rotation speed and the milling time are discussed. The densification kinetics of the mechanically alloyed powder during the process of spark-plasma sintering is analyzed. An optimal set of the compaction processing parameters, including the maximum temperature, the dwell time, and the heating rate, is determined. The specifics of the densification are discussed in terms of the impact of major spark-plasma sintering parameters as well as the possible phase transformations occurring during compaction processing.
An ambiguity in the available experimental data on the presumably faster spark-plasma sintering (SPS) densification kinetics compared with conventional hot pressing of powders is pointed out. A hypothesis of the major impact of the evolution of the inter-particle contact area on the densification rate is put forward. It is argued that properly controlled interplay between surface diffusion and external pressure-imposed creep provides better efficiency of the SPS process. The formulated ideas can be used for the SPS pressure–temperature cycle optimization.