1.4542 is a stainless steel hardenable martensitic chrome-nickel steel, stabilized with niobium.This steel grade reaches a very high yield strength in acured condition. Based on its good properties i.ee. the wear ressistance and the good corrosion resistance it can be found in a wide range of industries, i.e. the aircraft or aerospace industry or the plant engineeringg. It iss being delivered either in solution an-nealed or hardened condition. In a hardened condition it is being delivered and defined in several strength levels with associated me-chanical propertie.
Chemical Composition
| Chemical Element | Present % |
| C | 0.0 – 0.07 |
| Cr | 15.00 – 17.00 |
| Mn | 0.0 – 1.50 |
| Si | 0.0 – 0.70 |
| P | 0.0 – 0.04 |
| S | 0.0 – 0.03 |
| Ni | 3.00 – 5.00 |
| Cu | 3.00 – 5.00 |
| Mo | 0.0 – 0.60 |
| Nb | 0.0 – 0.45 |
| Fe | Balance |
Properties
| Physical Property | Value |
| Density | 7.75 g/cm³ |
| Thermal Expansion | 10.8 x10^-6 /K |
| Modulus of Elasticity | 196 GPa |
| Thermal Conductivity | 18.4 W/m.K |
| Electrical Resistivity | 0.8 x10^-6 Ω .m |
Corrosion Resistance
Precipitation hardening stainless steels have moderate to good corrosion resistance in a range of environments. They have a better combination of strength and corrosion resistance than when compared with the heat treatable 400 series martensitic alloys. Corrosion resistance is similar to that found in grade 304 stainless steel.
In warm chloride environments, 17-4 PH is susceptible to pitting and crevice corrosion. When aged at 550°C or higher, 17-4 PH is highly resistant to stress corrosion cracking. Better stress corrosion cracking resistance comes with higher ageing temperatures.
Corrosion resistance is low in the solution treated (annealed) condition and it should not be used before heat treatment.
Cold Working
Cold forming such as rolling, bending and hydroforming can be performed on 17-4PH but only in the fully annealed condition. After cold working, stress corrosion resistance is improved by re-ageing at the precipitation hardening temperature.
Hot Working
Hot working of 17-4 PH should be performed at 950°-1200°C. After hot working, full heat treatment is required. This involves annealing and cooling to room temperature or lower. Then the component needs to be precipitation hardened to achieve the required mechanical properties.
Heat Treatment
The key to the properties of precipitation hardening stainless steels lies in heat treatment.
After solution treatment or annealing of precipitation hardening stainless steels, a single low temperature “age hardening” stage is employed to achieve the required properties. As this treatment is carried out at a low temperature, no distortion occurs and there is only superficial discolouration. During the hardening process a slight decrease in size takes place. This shrinking is approximately 0.05% for condition H900 and 0.10% for H1150.
Weldability
Precipitation hardening steels can be readily welded using procedures similar to those used for the 300 series of stainless steels.
Grade 17-4 PH can be successfully welded without preheating. Heat treating after welding can be used to give the weld metal the same properties as for the parent metal. The recommended grade of filler rods for welding 17-4 PH is 17-7 PH.
Applications
Due to the high strength of precipitation hardening stainless steels, most applications are in aerospace and other high-technology industries.
- Gears
- Valves and other engine components
- High strength shafts
- Turbine blades
- Moulding dies
- Nuclear waste casks