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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.
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. thermodynamic calculation and experiments indicate that the replacement 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. 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 inferr ed that the decrease of amount and size of precipitates accounts for the changes of the mechanical properties.