Effect of composition fluctuations on the microstructural evolution and properties in the high carbon high chromium stainless tool steel

This study systematically analyzes the carbide dissolution during austenitization and the effect on hardness and corrosion resistance in two 19Cr20MoV5W-series powder metallurgical stainless tool steels (18C6W and 19C5W) with subtle compositional differences. Through electrolytic extraction, particle size analysis, and multi-scale characterization (SEM-EDS/XRD/TEM), combined with Thermo-Calc simulations, we find out that even negligible fluctuations in C and W content significantly alter the M 23 C 6 carbide dissolution temperatures (1051 °C for 18C6W vs. 1005 °C for 19C5W). Under identical heat treatment conditions, 18C6W retains M 7 C 3 , M 23 C 6 , and VC carbides, while 19C5W contains only M 7 C 3 and VC. These differences delay the hardness peak in 19C5W, demanding higher austenitizing temperatures (1110 °C vs. 1075 °C) to achieve comparable peak hardness. As compared with 18C6W, the improved corrosion resistance in 19C5W was also postponed during austenitization. These results elucidate the critical role of composition in carbide evolution, providing a theoretical basis for optimizing heat treatment processes to ensure consistent high performance in industrial applications demanding both hardness and corrosion resistance.