Topics mentioned :Nitriding, Nitro carburising, Boronising. Easy and Simple PPt.

1. -V. SAI GAYATHRI
18103091
ASP-5B

2. • Nitriding is a heat treating process that diffuses nitrogen into the
surface of a metal to create a case-hardened surface.
• Nitriding of steels produces less distortion and deformation than
either carburizing or conventional hardening.
• These processes are most commonly used on low-carbon,low-
alloy steels.
• However they also used on medium and high-carbon
steels,titanium,aluminium and molybdenum.

3. • Case-hardening process
• Solid ferrous alloy
• Diffuse nitrogen
• At some suitable temperature.
There are three methods used for nitriding
• Gas nitriding
• Salt bath nitriding
• Plasma nitriding

4. • Nitrogen introduction
• surface of a solid ferrous alloy
• nitrogenous gas
• Ammonia
• case-hardening process
 Chemical reaction
• nitrogen and iron
• core properties not effected
 temperature range
• 495-565 0 C
• below tempering temperature
 White layer By-product
• Thin
• Hard Iron Nitride
GAS NITRIDING FURNACE

5. Chemical Reaction:

6.  SALT BATH NITRIDING
• Thermo-chemical diffusion treatment
• Hardening components with Repeatability
• Use salt nitrogen-containing
• salt bath,at sub critical temperatures
• higher diffusion nitrogen
• Corrosion protection

8. PLASMA NITRIDING
ARRANGEMENT
• vacuum chamber
• pressure=0.64 pa
• surface cleaning
• intense electric field
PROCESS
– control gas flow
– N,H,CH4
– Ionization by voltage
– Blue violet glow
– Wear Resistant Layer

10. Advantages:
• The surface is hard and tough, combined with good wear
resistance.
• The fatigue strength is increased during nitriding by 30 to 100%
• The corrosion resistance is somewhat higher and with nitriding
followed by oxidation much higher
• The resistance against abrasive and adhesive wear is good.
• No machining is required after nitriding
• It increase the tensile strength and yield point.
• Reduced distortion due to lower tempeature

11. Disadvantages:
• Toughness and impact resistance decrease
• Asymmetric products could buckle due to unequal cooling
effects
• Maximum dimensions are determined by the furnace
dimensions
• Blind holes cannot be treated during plasma - nitriding.
• Ammonia can produce harmful effects
• Only special alloy steels can be satisfactorily treated.
• High cost of nitriding process
• If a nitrided component is accidentally overheated,the surface
hardness will be lost completely and the component must be
nitrided again.

12. AIRCRAFT INDUSTRY

13.  AUTOMOTIVE INDUSTRY

14. INTERNAL COMBUSTION ENGINES
COMPRESSORS

15.  CRANK SHAFTS,CAMSHAFTS,GEARS ETC.

16. TOOLS AND DIES ETC.

18. • Nitrocarburising is a variation of the case hardening process.
• It is a thermochemical diffusion process where nitrogen, carbon,
and to a very small degree, oxygen atoms diffuse into the surface
of the steel part.
• Forming a compound layer at the surface, and a diffusion layer.
• Nitrocarburising is a shallow case variation of the nitriding process.
• This process is done mainly to provide an anti-wear resistance on
the surface layer and to improve fatigue resistance.

19. • The nitrocarburizing process consists of three principal steps:
 Heating
 Diffusion at the nitrocarburizing temperature and
 Cooling.
• Pre-heating to accelerate the nitrocarburizing process and post-
oxidation to improve corrosion resistance are optional steps.
• Nitrocarburising is carried out at sub-critical temperatures ranging from
560 to 580°C.
• The composition of the atmosphere is a very important parameter in
gaseous nitrocarburizing.
• The atmosphere consists of nitrogen (N2), ammonia (NH3), carbon
dioxide (CO2) and hydrogen (H2).

20. • Carbon dioxide decomposes into carbon monoxide which together with
hydrogen is needed for the transfer of carbon to the steel surface.
• the diffusion of nitrogen and carbon into the surface of carbon steel to
give a somewhat harder case and soft core with a very thin compound
layer on the surface.
 The flow rate of different gases in each process step are plotted in
figure

21. ADVANTAGES:
• Relative low cost;
• High resistance to wear;
• Excellent scuffing and seizure resistance;
• Fatigue properties improved by up to 120%;
• Considerably improved corrosion resistance;
• Good surface finish;
• Negligible shape distortion;
• Predictable growth characteristics; and
• Alloy substitution – plain carbon steels replacing low alloy steels.

22.  PUMP COMPONENTS
IMPELLOR HOUSINGS,PLUNGERS ETC.

23. CRANKSHAFTS,GEARS ETC.

24.  MILLITARY TECHNOLOGY

25.  Boriding is thermochemical surface hardening method which can be
appilied to a wide range of ferrous,nen-ferrous & cermet materials.
 Here, boron atoms are diffused into surface of a metal component.
 The surface boride may be in the form of either a single phase or
double phase boride layer
PROPERTIES OBTAINED:
• wear resistance.
• Improved hardness (1300-2000HV is possible).
• Thermal stability.
• Resistance to corrosion by acids.
• Reduced coefficient of friction.
• Increased galling/cold-welding resistance.

26.  Applied to carbon and tool steels
 Medium: pack or gas
 Pack process:
• Compounds of the element boron are vaporized
• Then,it is made to react with steel and other alloys to convert a
diffused layer at the surface of parts to an extremely hard compound,
which has superior wear resistance.
• Parts are borided by heating them in a furnace in an atmosphere
containing these boron compounds.
• The parts, heated to temperatures in the 1800°F range for several
hours, can be used directly after the boriding treatment in applications
requiring extreme wear resistance.

27. • The thickness of boride layer obtained is determined by the
temperature, and as well as material composition. Generally low to
medium carbon and stainless steel parts benefit from boriding.
• After boriding, the parts may hardened and tempered or quenched to
restore core properties.

28. ADVANTAGES:
• Increase resistance of alloy steels to sulphuric,phosphoric, and
hydrochloric acid
• Selective hardening is possible
• Can be polished to high finish
• Can be applied to irregular shapes
• Increases tool and mold life by improving resistance to abrasive,
sliding annd adhesive wear
• low coefficient of fricion
DISADVANTAGES:
• Distortion due to high temperature
• Poor fatigue and corrosion resistance

29. BORONIZED VALVES

30.  AUTOMOTIVE INDUSTRY
ENGINE DIESEL OIL PUMPS,GEARS ETC.

31.  TEXTILE INDUSTRY
GROOVED DRUMS ETC.