**5.1 Martensitic steels**

Since its development in the early 1990s, Cronidur 30 (X30CrMo 15-1 plus 0,4 % nitrogen) has been approved as high performace alloy for aerospace applications such as spindles, shafts and bearings. It is used as material for helicopter bearings, flap traps, fuel pumps etc. It excellent corrosion resistance combined with a high hardenability of 60 HRC makes it unique. The alloy has become an important material to industries as cutleries and knifes, general engineering, medicals (since it is free of nickel) and powder metallurgy.

Fig. 24. High precision bearing of Cronidur 30 [ETE-11].

higher than the influence on stacking fault energy. [Mudali & Raj, 2004] confirms that increased stacking fault energy does improve the SCC resistance. As nitrogen decreases the stacking fault energy it should detrimental to SCC. Carbon, due to the formation of wavy slip bands, should be theoretically beneficial. However, it appears that the role of nitrogen

The benefit of nitrogen alloying appears to be more oblique – the delay in M23C6 precipitation and improved pitting corrosion resistance has been recognized to be beneficial

High nitrogen steels are characterized through an interesting material profile that has led to a variety of demanding applications. The following will provide an overview about today´s use of HNS alloy, please note it reflects only pressurized alloys, i.e. PESR alloys. Any air

Since its development in the early 1990s, Cronidur 30 (X30CrMo 15-1 plus 0,4 % nitrogen) has been approved as high performace alloy for aerospace applications such as spindles, shafts and bearings. It is used as material for helicopter bearings, flap traps, fuel pumps etc. It excellent corrosion resistance combined with a high hardenability of 60 HRC makes it unique. The alloy has become an important material to industries as cutleries and knifes,

general engineering, medicals (since it is free of nickel) and powder metallurgy.

on SCC is fairly complex and depends on the alloy design and corrosion media.

against SCC since pits are likely to initiate SCC.

melted nitrogen alloy steels will not be part of this chapter.

Fig. 24. High precision bearing of Cronidur 30 [ETE-11].

**5. Applications of HNS** 

**5.1 Martensitic steels** 

Fig. 25. Extruder screw, Cronidur 30 [ETE-11].

A heat resistant alloy is based on X15CrMoV12-1 and contains 0,2 % nitrogen (trade name HNS 15). It precipitates fine V(C,N) and provides a good creep resistance and heat resistance up to 650 °C. Above this temperature the appearance of Laves-phase restricts its usage.

A Molybdenium-free version is known as HNS 28 and consists of X28Cr13 with 0,5 % nitrogen. Its purpose was the closed-die casting industry where a good polish and corrosion resistance is required.
