At what temperature is nitriding conducted?
Around 500°C
How is the nitriding potential calculated?
pNH3 is the partial pressure of ammonia in the nitriding atmosphere.
pH2 is the partial pressure of hydrogen.
The exponent 3/2 comes from the fact that three moles of hydrogen are produced for every two moles of ammonia that decompose. This means that the hydrogen concentration has a stronger inhibiting effect on the nitrogen uptake, which is why its pressure appears to the 3/2 power in the denominator.
What is the Nitride concentration in the respective layers?
Which nitrides are formed in combination with iron?
In which way is the diffusion layer thickness dependant on the time?
Dn: diffusion layer thickness
What is the advantage of a duplex treatment?
The increasing of both good properties and increasing the load bearing capabilities
Which process step needs to be conducted for increasing corrosion resistance in nitrocarburizing?
A hort oxidation at 450°C
=> formation of magnetite layer
What is the Ammonia dissociation reaction?
How much is thr rough solubility of Nitrogen in alpha Iron?
<0.2 wt%
What are the processing parameters of Nitriding?
Thickness
Composition
Constitution
Porosity
From what originate bubbles in the surface layer of FeN?1
change in equilibrium due to pressure difference between atmosphere of oven and air pressure
Describe the typical microhardness profile of the finished product over the depth.
Which two metallographic hardening principles apply for Nitriding?
Solid solution hardening (N)
Precipitation hardening (nitrides)
How is the Fe Nitride forming potential compared to other elements?
Lower
What can cause failure in overnitriding?
Nitride accumulation at grain boundaries
With which quantity is the nitriding potential calculated?
The chemical activity of amonia, nitrogen and hydrogen
Roughly describe the shape of the compound layer thickness over nitriding time graph.
How is the case depth (diffusion layer thickness) over Nitriding time calculated?
How does the alloy concentration effect the penetration depth of the Nitrogen?
The higher the alloy concentration the lower the penetration depth.
Name the marked components
What are the advantages of plasma nitriding?
optimum control of N transfer at the workpiece surface
lower process temperatures
Minimal wastes
low energy consumption
automatic process
What are the disadvantages of plasma nitriding?
limited size of treated parts
limited productivity
difficult for components with little surface
low pentetration power in irregular shapes
What are the benefits of nitriding?
increased surface hardness
improved wear resistance
improved fatigue resistance
Improved thermal stability
How does plasma nitriding work?
Positive ionizing of the Nitrogen atoms. Acceleration toward the workpiece and penetration of the surface and subsequent depositing.
Name two applications of the the nitriding process.
Hardening screws
Hardening forging dies
Is nitriding a good protection against corrosion?
No because the diffusion layer between compund layer and the unnitrided core is made more reactive.
What are the differences between nitriding and nitrocarburization?
Nitrogen and Carbon transferred
shorter process at higher temperature in salt bath
NC layer has good lubrication properties due to HCP structure
strong improvement in corrosion resistance if followed by short oxidation at 450°C where a magnetite layer is produced
What are the three types of nitriding processes?
gas nitriding
salt bath nitriding
plasma nitriding
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