Corrosion Properties of a Ti-15Mo/TiB Composite Produced by Spark Plasma Sintering

Corrosion properties of Ti-15Mo/TiB metal-matrix composite in the initial as-sintered condition and after multiaxial forging (MAF) at 700 degrees C were studied in comparison with commercially pure (CP) Ti and Ti-15wt.% Mo alloy. All the specimens were produced by spark plasma sintering at 1400 degrees C using corresponding powder mixtures. Both CP hcp Ti and bcc Ti-15Mo had microstructures with a grain (or colonies of lamellae) size of similar to 20 mu m. Microstructure of the as-sintered composites consisted of TiB whiskers heterogeneously distributed within the bcc Ti matrix. Intensive shortening of TiB whiskers occurred during the MAF. Hardness of Ti increased due to an addition of Mo; hardness of the composites increased further in comparison with Ti-15Mo. After MAF the hardness did not change noticeably. Corrosion tests conducted using the electrochemical method showed some improvement due to an addition of Mo and TiB reinforcements into the Ti matrix. MAF also increased corrosion properties, however the development of pitting corrosion at potentials E approximate to 4000 mV can be expected.