| 【文章摘要】 In order to investigate the effect of N on the microstructure and room temperature mechanical properties of new-type high silicon martensitic heat-resistant steels,three steels containing the same total content of C and N but different N contents have been designed and prepared according to the thermo-calc calculation.The thermodynamic calculation and experiments indicate that the replacing of C by N changes the kind and volume fraction of precipitates of the high Si martensitic steel significantly.Along with the N content increasing,the precipitates in the samples after 750 °C tempering change from(Cr23C6? VN ? TaC) to(Cr23C6? VN ? TaC ? TaN) and finally to(Cr23C6? VN ? Cr2N)according to both experimental results and thermodynamic calculations.The room temperature mechanical tests show that the strength of the steel decreases as the N content increases.However,the Charpy impact toughness increases with N content increasing.According to the calculation and SEM observation,it is inferred that the decrease of amount and size of precipitates accounts for the changes of the mechanical properties. |