The effect of W on microstructural changes during creep of HT9M

Quantitative microstructural investigations (martensite lath width, particle size, chemical composition of particle) have been carried out using transmission electron microscopy (TEM). The enrichment of Cr in M23C6 carbide and the precipitate of Laves phase are occurred during creep deformation. The enrichment was delayed by the addition of tungsten, but the precipitate of Laves phase was not. The coarsening of precipitates and the increase of lath width were restricted by the addition of tungsten. HT9M and tungsten added HT9M steels had a good thermal-induced microstructural stability, so the coarsening of precipitates and increase of lath width were very small in the head of crept specimen