Processes

Processes and methods used for Wear protection

SMAW(Shielded Metal Arc Welding )

also known as

Manual Metal Arc Welding (MMA ) , or Stick welding

+ plus

Wide range of alloys (electrodes) available.

Low cost of equipment , available in most workshops.

Easy to apply no special skills required :

– minus

Relative high dilution of weld deposit (20-40 % )

2– 3 layers may be required to achieve maximum wear properties

Low Deposition rate ( between 1– 3 kg/ h )

(FCAW) Flux Cored Wire Welding (GMAW ) gas metal arc welding

+ plus

High deposition rates from 2– 11 kg /h

Large range of alloys available to suit most application .

Easy to use.

– minus

Relative high dilution of weld deposit (20-40 % )

2– 3 layers may be required to achieve maximum wear properties

TIG (GTAW) Gas Tungsten Arc welding

+ plus

Low dilution,

Good control of weld deposit

Low dilution (5-15 %)

Ideal for Hard facing of tools & dies

– minus

Low deposition rates

Limited range of alloys available.

High welding skill necessary

Gas (oxy-acetylene) Hard facing (OFW)

+ plus

Excellent control over the deposit shape.

Minimum dilution of weld deposit (0-5 %)

Slow heating and cooling minimizes thermal shock of part

Equipment easily available at low cost

– minus

High heat input necessary

Low deposition rate

Not suitable for very large components

Powder Flame Spraying (Spray& Fuse)

A two step process where the powder is sprayed with a thermal spray gun and thereafter fused to achieve a dense coating

+ plus

Low cost of equipment ,easy to use

Only low dilution with base metal

Exact control over deposit shape and thickness

Wide range of powders available

– minus

High heat input necessary for spray & fuse coating

(PTA) Plasma Transferred Arc surfacing with powders classified as nickel base, cobalt base and iron base

+ plus

Low dilution of weld deposit (5-10 %)

Exact control over deposit thickness and shape,

Complete metallurgical bond between base metal and powder alloy

Automation is possible.

High deposition rate : up to 20 kg/h

– minus

Relative high cost of equipment

Limited mobility

High operator skill necessary

Other Processes used

  • HVOF (High –Velocity Oxy –Fuel) spraying)
  • WFS (Wire flame spray)
  • CGS (Cold gas spray)
  • AS (Arc spray )

Processes Used for Wear protection

HVOF (High –Velocity Oxy –Fuel) spraying)

+ plus

Low heat input, therefore workpiece remains relative cool with little change to either workpiece or sprayed material

Exact control over deposit thickness and shape and extremely thin coatings van be produced

Can be automated

Deposition rate from 2-15 kg/h

– minus

High cost of equipment

Limited mobility

Electric Arc Spraying (TWAS) (twin arc wire spraying)

+ plus

High deposition rates (8– 20 kg/h)

Preferred process for corrosion protection

No or only limited dilution of deposit

Can be automated

Good control over deposit thickness & shape

– minus

Relative high cost of the equipment

Limited mobility

Exposure to electric arc and fumes ,

SAW (submerged arc welding)

+ plus

fast deposition

Ideal for large parts such as rollers etc/

Suitable for automatic application

Produces sound and smooth deposits

– minus

Limited range of alloys available

Not suitable for smaller parts

Special equipment necessary

High dilution