Surface Treatment ProcessSurface Treatment Process

Advantages:Advantages: Control Friction and wearControl Friction and wear Improve resistance to corrosion and oxidationImprove resistance to corrosion and oxidation Change physical propertyChange physical property Alter dimensionAlter dimension Improve appearance and provide glossy textureImprove appearance and provide glossy texture Reduce costReduce cost

IntroductionIntroduction:: The surface of the manufactured product must be The surface of the manufactured product must be processed to ensure certain characteristics and properties, which is processed to ensure certain characteristics and properties, which is known as surface treatmentknown as surface treatment

Classification :Classification : Surface treatment process can be divided into two major Surface treatment process can be divided into two major

categories:categories:

1. Treatment that cover the surfaces1. Treatment that cover the surfaces

Such as organic and inorganic coatings (overlay coatings).Such as organic and inorganic coatings (overlay coatings).

2. Alter the Surface 2. Alter the Surface

Such as hardening, high-energy treatments, thin diffusion Such as hardening, high-energy treatments, thin diffusion

treatment , heavy diffusion treatments and special treatmentstreatment , heavy diffusion treatments and special treatments

(diffusion coatings, thermal treatments and mechanical surface(diffusion coatings, thermal treatments and mechanical surface

treatments) treatments)

Treatment that cover the surfacesTreatment that cover the surfaces

Conversing Coatings:Conversing Coatings: 1. Oxide coatings :1. Oxide coatings :

• Gun Bluing type oxidationGun Bluing type oxidation

• Chemical bathChemical bath

• AnodizingAnodizing

2. Phosphate coatings2. Phosphate coatings 3. Chromate coatings3. Chromate coatings

Electroplating:Electroplating:

It is electrochemical process by which metal is deposited on a substrate by passing current through the bath.

Anode (+): The material to be deposited

Cathode(-): Material to be coated

The bath is filled with an electrolyte, which has metal to be coated in ionic form.

Note:

1. Maximum thickness of deposit is about 0.05mm

2. Materials such as chromium, nickel, cadmium, copper, zinc are common plating materials

3. Applications includes hydraulic shaft and engine cylinders, etc.

Common Coating Metals Common Coating Metals Zinc - plated on steel products such as Zinc - plated on steel products such as

fasteners, wire goods, electric switch fasteners, wire goods, electric switch boxes, and sheetmetal parts as a sacrificial boxes, and sheetmetal parts as a sacrificial barrier to corrosionbarrier to corrosion

Nickel - for corrosion resistance and Nickel - for corrosion resistance and decorative purposes on steel, brass, zinc decorative purposes on steel, brass, zinc die castings, etc.die castings, etc. Also used as base coat for chrome plate Also used as base coat for chrome plate

Tin - widely used for corrosion protection in Tin - widely used for corrosion protection in "tin cans" and other food containers "tin cans" and other food containers

Copper - decorative coating on steel Copper - decorative coating on steel and zinc, either alone or alloyed as and zinc, either alone or alloyed as brassbrass Also important in printed circuit boards Also important in printed circuit boards

Chromium - decorative coating Chromium - decorative coating widely used in automotive, office widely used in automotive, office furniture, and kitchen appliancesfurniture, and kitchen appliances Also one of the hardest electroplated Also one of the hardest electroplated

coatings for wear resistancecoatings for wear resistance

Precious metals (gold, silver) - Precious metals (gold, silver) - plated on jewelryplated on jewelry Gold is also used for electrical contactsGold is also used for electrical contacts

Electro-less plating:Electro-less plating: Also known as autocatalytic plating.Also known as autocatalytic plating. Which involves deposition without any current applied. Which involves deposition without any current applied. The process is a chemical reaction and is autocatalytic.The process is a chemical reaction and is autocatalytic.

Electro-less plating involving a nickel sulfate bath has reaction ofElectro-less plating involving a nickel sulfate bath has reaction of

NiSONiSO44 + NaH + NaH22POPO22 + H + H22O O →Ni Plating + Na→Ni Plating + NaHH22POPO3 3 + + HH22SOSO44

The plating thickness tends to be uniform compared to The plating thickness tends to be uniform compared to

electroplating.electroplating. The coating thickness usually less than 50The coating thickness usually less than 50µm in practice due to low µm in practice due to low

deposition rate.deposition rate. Autocatalytic plating is used widely for machine frame, base plates, Autocatalytic plating is used widely for machine frame, base plates,

fixture.fixture. This process is can also be used to coat non-conducting materials, This process is can also be used to coat non-conducting materials,

such as plastics and ceramics.such as plastics and ceramics.

Hot DippingHot Dipping

Metal substrate (part) is immersed Metal substrate (part) is immersed in a molten bath of a second in a molten bath of a second metal; when removed, the second metal; when removed, the second metal is coated onto the first metal is coated onto the first

Common substrate metals: steel Common substrate metals: steel and ironand iron

Coating metals: zinc, aluminum, Coating metals: zinc, aluminum, tin, and lead tin, and lead

Primary purpose is corrosion Primary purpose is corrosion protectionprotection

Hot Dipping Hot Dipping ProcessesProcesses

GalvanizingGalvanizing - zinc coated onto steel - zinc coated onto steel or iron or iron Most important hot dipping processMost important hot dipping process

AluminizingAluminizing - coating of aluminum - coating of aluminum onto a substrate onto a substrate Excellent corrosion protection, in some Excellent corrosion protection, in some

cases five times more effective than cases five times more effective than galvanizinggalvanizing

TinningTinning - coating of tin onto steel for - coating of tin onto steel for food containers, dairy equipment, food containers, dairy equipment, and soldering applicationsand soldering applications

Hard facing process:Hard facing process: Hard facing is a process in which, weld materials, with superior Hard facing is a process in which, weld materials, with superior

properties than base, are applied to the substrateproperties than base, are applied to the substrate .. Two layers total 3-6mm thick are applied to reduce surface hardness Two layers total 3-6mm thick are applied to reduce surface hardness

dilution.dilution.

CategoryCategory ProcessProcess

Arc weldingArc welding

Flux core arc welding (FCAW)Flux core arc welding (FCAW) Gas metal arc welding (GMAW)Gas metal arc welding (GMAW) Gas tungsten arc welding (GTAW)Gas tungsten arc welding (GTAW) Plasma arc welding (PAW)Plasma arc welding (PAW) Shield metal arc welding (SMAW)Shield metal arc welding (SMAW) Submerged arc welding (SAW)Submerged arc welding (SAW)

Torch weldingTorch welding

Oxy/fuel gas welding (OFC)Oxy/fuel gas welding (OFC) Electron beam welding (EBM)Electron beam welding (EBM) Electro slag welding (ESW)Electro slag welding (ESW)

Other weldingOther welding Furnace Braze (FB)Furnace Braze (FB) Laser beam welding (LBM)Laser beam welding (LBM)

The Most common hard facing materials are nickel alloys and iron / The Most common hard facing materials are nickel alloys and iron / chromium alloys used in wear resistance and high stress abrasion.chromium alloys used in wear resistance and high stress abrasion.

Metal AlloyMetal Alloy PurposePurpose

Cobalt-base alloysCobalt-base alloys Copper-base alloysCopper-base alloys Iron chromium alloysIron chromium alloys Manganese steelManganese steel Nickel-base alloysNickel-base alloys Tool steelTool steel Tungsten carbideTungsten carbide

Wear and corrosion resistanceWear and corrosion resistance Rebuilding worm machinery Rebuilding worm machinery partsparts High stress abrasionHigh stress abrasion Wear applicationWear application Metal to metal wear resistanceMetal to metal wear resistance Tooling, wear applicationTooling, wear application High stress abrasionHigh stress abrasion

Table: Common materials for hard facing

Thermal spraying:Thermal spraying:

Thermal spraying processes form a continuous coating by melting the Thermal spraying processes form a continuous coating by melting the consumable material into droplets and impinging these droplets on the base consumable material into droplets and impinging these droplets on the base material.material.

The coating material can be in the form of wire , rod or powder.The coating material can be in the form of wire , rod or powder. The surfaces to be sprayed are first cleaned and roughened to improve bond The surfaces to be sprayed are first cleaned and roughened to improve bond

strength and coatings are applied.strength and coatings are applied. The applications included aircraft engine components requiring resistance to wear The applications included aircraft engine components requiring resistance to wear

and corrosion .and corrosion . The mechanism of bonding to the surface in thermal spraying is, both mechanical The mechanism of bonding to the surface in thermal spraying is, both mechanical

locking and atomic interaction. locking and atomic interaction.

Common thermal spraying processes:Common thermal spraying processes:

1.1. Flame spraying (FLSP) Flame spraying (FLSP)

2.2. Plasma arc spraying (PSP)Plasma arc spraying (PSP)

3.3. Electric arc spraying (EASP)Electric arc spraying (EASP)

4.4. Detonation gun (D-GUN)Detonation gun (D-GUN)

5.5. High velocity oxy/fuel (HVOF)High velocity oxy/fuel (HVOF)

Flame spraying (FLSP)Flame spraying (FLSP) : : In this process uses 2760In this process uses 276000C oxyacetylene flame is used to C oxyacetylene flame is used to

melt the target which may be powder, rods or wires.melt the target which may be powder, rods or wires.

Fuel & oxygen

Coating Metal

Air passage

Spray nozzle

Sprayed material

ProcessProcess TargetTarget Energy sourceEnergy source

1.1. Flame spraying (FLSP)Flame spraying (FLSP)

2.2. Plasma arc spraying (PSP)Plasma arc spraying (PSP)

3.3. Electric arc spraying (EASP)Electric arc spraying (EASP)

4.4. Detonation gun (D-GUN)Detonation gun (D-GUN)

5.5. High velocity oxy/fuel (HVOF)High velocity oxy/fuel (HVOF)

Powder, rod or wirePowder, rod or wire

PowderPowder

Wire (motor driven)Wire (motor driven)

PowderPowder

PowderPowder

Oxy acetylene flamOxy acetylene flam

Plasma gunPlasma gun

Electric arcElectric arc

Spark ignition of Spark ignition of explosives explosives

Oxygen, hydrogen, fuelOxygen, hydrogen, fuel