The effect of W and N addition on the mechanical properties of 10Cr steels

Abstract

The effect of W and N on the creep properties and microstructural degradation in 10Cr steels was studied. Creep testing was performed to determine the creep rupture strength and minimum creep rate. Transmission electron microscopy was used to observe the microstructural degradation during the creep deformation. W and N which were added to the 10Cr steel increased the creep rupture strength and decreased the minimum creep rate. As W and N were added, the thermal stability of the subgrain and carbide was improved, thus the growth of the subgrain and carbide during creep deformation was restricted. In W added steel, the Laves phase played an important role in increasing creep rupture strength. But the impact toughness was rapidly degraded by the addition of W after aging at 600 o C for 5000 hours. So one must evaluate more accurately the effect of the Laves phase on long term creep and impact properties. In N added steel, V(C, N) was precipitated in the lath boundary and within the lath. The size of the precipitates was 20-50 nm. The increase of creep rupture strength in N added steel may be due to the precipitate of the V(C, N). Future tests are required to clarify the effect of N on creep and impact properties.

The Impact of Prenitriding on the Microstructure and Mechanical Properties of the Carburized Surface Layer in a Martensitic Stainless Steel

“…It has also been revealed that the thermal stability of nitrides is superior to carbides because the enthalpy of formation of nitrides was higher than that of carbides. [ 36 ] As a result, the pinning effect of the carbonitrides was more obvious in the PN carburized specimen, as shown in Figure 5d,g. The variation in austenite grain size of the case layer in PN carburized specimen was induced by the combined effect of carbon and nitrogen.…”

Effects of alloying elements on the thermal fatigue properties of the 15wt% Cr ferritic stainless steel weld HAZ

“…The equilibrium mole percent of the precipitates was affected by the addition of W. In addition, the dissolution temperature of the Laves phase increased with W addition. The increasing content of refractory element such as W causes the stabilization of intermetallic compounds or precipitates at higher temperatures [12][13][14]. Due to the stabilizing effect of Laves phase by W addition, its dissolution temperature is increased and that can affect the size of precipitates.…”

Formation of Nano M₂X Particles by a Tempering in High Cr Ferritic/Martensitic Steel

“…Nitrides are more stable and less soluble than the corresponding carbide because the enthalpy of formation of nitrides is higher than that of carbides. So an addition of nitrogen contributes to an increase of the creep rupture strength [6].…”