Microstructure and high-temperature tensile behavior of modified H13 steel with the addition of tungsten, molybdenum, and lowering of chromium

H13 can hardly meet the requirements of advanced manufacturing industries due to its insufficient strength at elevated temperatures. In the present work, modified CXN02 and CXN03 based on H13 with more molybdenum, tungsten content, and less chromium content were prepared. The yield strength of CXN03 is 1714 MPa at 25 degrees C, which is 106% of CXN02 and similar to 111% of H13. With the test temperature increase, the yield strength of all materials decreased. As the test temperature raised to 650 degrees C, the yield strengths of CXN02 and CXN03 became similar to about 700 MPa, which is about 64% higher than that of H13. As-tempered CXN03 has a finer average grain size, higher dislocation density, and larger volume fraction of precipitations than as-tempered CXN02. The additional W and Mo in CXN03 allowed more M6C to present in as-annealed CXN03, thus more undissolved carbides that could pin prior austenite grains exist in as-quenched CXN03, refining the grains. The yield strength at room temperature was correlated with microstructure by a mathematical model. Calculations revealed that the higher strength of CXN03 is mainly attributed to the higher dislocation density and finer grain size. The brittle-to-ductile transition temperature is around 400 degrees C for both materials, and the deformation mechanism evolution with the temperature increase from 25 to 650 degrees C is briefly discussed.