1. Modern Methods of Ferritic Nitrocarburizing (FNC)
H-13 section
28” dia 48” depth
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
open basket
Open bed at temperature
Loaded basket, ready for carousel
Removal from fluidized quench

2. Ferritic Nitrocarburizing (FNC) How we got here
1900’s – Dr. Adolph Fry
Discovered that Nitrogen and Iron had affinity to one another.
Developed nitrogen iron equilibrium table
Nitralloy steels
Studied effect of adding other alloys Vanadium, Tungsten, Manganese, Molybdenum, Titanium
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

3. Ferritic Nitrocarburizing (FNC) Continued 2
1900’s Adolph Machlet – New Jersey
American Gas Company - Elizabeth
Applied for patents which were received June 24, 1913
US saw no commercial benefit at the time
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

4. Ferritic Nitrocarburizing (FNC) Continued 3
1927 Pierre Aubert – Chicago
At SME convention presented research for practical applications in Europe
Included railway steel, machine tools, auto, aviation.
Benefits – hard surface, core not changed, high wear, unaffected by temper, corrosion resistance.
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

5. Ferritic Nitrocarburizing (FNC) Continued 4
1928 – McQuaid and Ketchum
Timken – Detroit Axle Co.
Metallurgists – practical applications
Used work of Fry and Machlet as pivot point
1929 – Robert Sergeson
Central Alloy Steel – Canton, OH
Varying Al content in nitro alloy steel with effect of nickel
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

6. Ferritic Nitrocarburizing (FNC) Others
V. O. Homberg & J.P. Walsted - MIT
Effect of varying temperature – white layer
Equipment preheat and decarburization effect
Dr. Carl F. Floe – Assoc MIT
Continued study of white (epsilon) layer
The Flow Process – methods to change compound layer
Eventually this research lead to “Ion Nitriding” – in effort to shorten cycle times, reduce distortion, and improve metallurgical properties.
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

7. Types of Nitriding Fluidized Bed Nitriding and FNC Nitempering
Controlled Nitrocarburizing
Soft Nitriding
Triniding
Nitroc Process
Vacuum Nitrocarburizing
Nitrotec Process
Austenite Nitrocarburizing
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

8. FNC – Thermochemical Diffusion
Process where N2,C, and sometimes a very small degree of O2 atoms are diffused into the surface of a ferrous substrate forming a compound layer and subsurface diffusion layer.
Done in relatively short period of time at sub critical steel temperatures
Wear properties, Corrosion (solder), and improved fatigue resistance.
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

9. Prominent Developments FNC
Salt Bath Nitrocarburizing
Started about 55 years ago commercially.
1959 – Germany patented Tuffride
1970’s – EPA regs prohibiting cyanide base materials
Tufftride replaced with Melonite and French process called Sur-sulf
These two processes still in use today.
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

10. Prominent Developments FNC Continued
Gas – Originally patented in 1961 by Joseph Lucas Industries Ltd.
1965 – B. Presnosil Published results of study doing Gas.
During following quarter of a century – developed Triniding (NH3 and exothermic gas), Nitemper, Lindure and a two stage process (Deganit) from Germany
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

11. Fluidized (FNC) Bed Phenomenon
An 1879 patent discusses baking minerals under fluidized bed conditions
Bed of finely-divided heated particles, usually Aluminum oxide made to behave like a liquid by moving exothermic and reactive gases through the medium
Smooth or bubbly properties – determines fluidization quality.
Size and hetrogeneity (other offspring) of bubbles – influences rate of the solid mixing
Bed geometry, gas flow rate, type of gas distributor
Vessel features – baffles, screens, heat exchangers
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

12. Analogy of Fluidized Bed and Liquids
Plunging your hand into a fluidized bed (unheated of course) gives the sensation of placing your hand in a bucket of water. Light objects introduced in the bed will float if light enough.
Behaving as a liquid causes the entire introduced object (metal) to be in complete contact with the aluminum oxide separated by the reactive gas/gases that surround the media and cause diffusion and white layer creation.
The heat from the bed starts the diffusion
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

13. Fluidized (FNC) Heat Transfer Factors
Cleanliness of tool steel
Mild to aggressive alkaline bath at elevated temperature – bed & part contamination
Particle diameter – influences heat transfer
In practice 100 micro mm (.3940 micro inches)
Bed material density
Optimum value kg/cu m or lb/cu. ft.
Fluidized velocity of gas/gases
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

14. Optimizing heat transfer to bed
Optimizing gas/gases flow rate
Between 2 to 3 times the minimum fluidization velocity
Curve peaking
To high – particle entrapment – high gas consumption
To low - poor heat transfer – lack of uniformity
Bed screws do not provide consistency
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

15. Relationship of gas fluidization velocity to heat transfer rate
Heat transfer rate falls off rapidly
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

16. Relationship of Bed Temperature to necessary Flow Rate
Higher bed temperatures require less gas flow
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

17. Objective to get maximum heat transfer to part and optimize velocity of the gas/gases
Heat transfer rate falls off rapidly without optimized gas flow rate
Higher bed temperatures require less gas flow
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

18. Now a better way to attain repeatability - flow and heat
Computer control and automation
Adjustable ceramic screens
Eclipse valves with flow meters
Sensor feedback to computer controls and automation system
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
First Fully Automated System in the United States and Canada

19. H-13 after only 2 hours in bed (N2,NH3,CH4)
Vickers hardness from surface
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
Compound layer 5-20 microns = inches Diffusion layer microns = inches

20. Future Uses of Fluidized Beds
Development of Hard PVD (below 700o F) thermochemical surface treatments in Australia – grant by IR & D board
Coatings such as vanadium carbonitride, and chromium carbonitride at low temperature by diffusion-based treatments
Patents already applied for and equipment available to perform new range of low temperature surface treatments – Qab.
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

21. Nitrogen and Alloy based below 700o C Carbon based above 700o C
Range of coatings - QAB
Courtesy of QHT Ray Reynoldson
Nitrogen Based Nitriding Ferritic Austenitic Alloy Based Chromium Vanadium Titanium Niobium
Carbon Based Carburizing CD Carburizing Carbonitriding
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
Nitrogen and Alloy based below 700o C Carbon based above 700o C

22. Process to form CrCN - QAB
Courtesy of QHT Ray Reynoldson
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
Aluminum Oxide media to obtain CrCN is coated

23. Qab Profile for CrCN and Nitrocarburized structure
Hardness Profile - QAB
Courtesy of QHT Ray Reynoldson
Thickness controlled by time of processing
CrCN = 1550v
NitroC = 950v
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
Qab Profile for CrCN and Nitrocarburized structure

24. Distribution of Elements in White Layer
Courtesy of QHT Ray Reynoldson
Thickness controlled by time of processing
CrCN = 1550v
NitroC = 950v
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec
% of Cr highest near surface

25. Field test results CrCN
Courtesy of QHT Ray Reynoldson
V Notch Charpy testing of incoming H-13 should show a minimum of 8 ft. lbs according to NADCA spec

26. Badger Metal Tech, Inc. 262-252-3956 Toll Free 800-366-1973
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