Coatings

NELES®

Coating Materials for Metal-Seated Ball Valves

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JAMESBURY VALVE SOLUTIONS

Coating Materials for Metal-Seated Ball Valves

The importance of trimcoatingsMetal seated ball valves achieve sealing bymetal to metal contact between the ball andseat. When “soft” metals of similar hardnessslide against each other under evenmoderate pressure, galling occurs.Microscopic protrusions on the seatingsurfaces catch on each other, resulting insurface friction, heat buildup and plasticdeformation. Typically the damage getsworse as the valve cycles until it becomesinoperable due to seizure. If no coatings areapplied to the trim, galling will be visiblealmost as soon as the valve is cycled on thetest bench. Once installed in service, thevarious effects of difficult media wouldincrease wear rate exponentially.

Properly selected coatings reduce thefriction between the ball and seats allowingfor smooth sliding operation over manycycles, minimizing damage and wear due togalling, abrasion, erosion, particle impact,cavitation and thermal swings. Reducingfriction in the trim lowers the valve’soperating torque which has severaladvantages. Lower valve torque allows asmaller actuator to be used which is moreeconomical, results in smaller envelopedimensions of the assembly, improves signalresponse in control service and simplifiesselection of accessories to meet cycle speedtargets and other special requirements.

Selection of trim coatingsValve body, ball and seat materials areselected based on factors such as pressure,temperature and chemical compatibility.These criteria must also be considered whenchoosing trim coatings. Improper selectioncan cause almost instant failure of the valveupon startup. It is also important to notethat properly selected trim coatings cannotmake up for unsuitable base materials. Mostcoatings are porous to some degree and donot isolate the base material against theeffects of corrosive media. Base material andcoating must both be selected to meet thedemands of the application.

Metso’s NELES brand metal seated ball valves offer superior, long lastingperformance over a broad range of services in numerous industries. Everyapplication presents unique challenges that must be considered when determiningthe most suitable valve. Many choices are straightforward such as size, pressureclass, and body material, but one of the most critical decisions is often the leastunderstood and is sometimes overlooked. Proper selection of trim coating materialsis essential to ensure that a valve is configured to meet the demands of theapplication.

Photo courtesy of Deloro Stellite Group

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ElectroplatingCoatings are applied in a vat containingchromic acid and sulfates or fluorides ascatalysts. This process is used for ourstandard Hard Chromium plating.

S&F: Thermal Spray and Fuse.These coatings are fused in a vacuumfurnace or by flame. The size of the part tobe coated is limited by the capacity of thefurnace. Nickel Boron coating is appliedwith this method and is available on balls upto 16” size.

HVOF: High velocity thermal sprayingusing HVOF (High Velocity OxyFuel)These coatings are applied as a powdercombined with a high velocity jet ofcombustible gases. Carbide based coatingsare applied in this manner.

Thermal DiffusionAn element is diffused into the materialsurface to create a dense reaction zone withincreased surface hardness and resistance towear and impact. Corrosion resistancedepends on the properties of the basemetal.

PTA: Plasma Transfer Arc Welding:The coating material is welded to thesubstrate using either a powder or rodconsumable. This process is typically used toapply cobalt based alloys.

Coating Materials

Coating Application Processes

420 Stainless Steel applied using HVOF.

420 Stainless Steel applied using Plasma.

420 Stainless Steel applied using Arc Wire.

420 Stainless Steel applied using Flame Wire.

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Coating Materials

Overview of Coatings, Overlays,and Surface TreatmentsHard Chromium (HCr)Hard Chromium is the standard ball coatingfor most NELES ball valves and is suited to awide range of applications in clean liquidsand gases at moderate temperature andpressure. Its corrosion resistance isequivalent to stainless steel (AISI 316) withcertain limitations. The pH of the mediashould not be less than 2. HCr has noresistance to hydrochloric acid (HCl),hydrofluoric acid (HF) or sulfuric acid (H2SO4),and it should not be used with seawater,wet chlorine or other media with highchloride content.

Electroless Nickel Plating (ENP)Electroless Nickel Plating is generally used asa substitute for Hard Chromium whengreater corrosion resistance is required,primarily in services with pH<2. ENP can beapplied to cast iron and mild steels forcorrosion protection of the base metal.Physical properties of ENP vary based on thesubstrate, coating thickness, phosphoruscontent and method of heat treatment afterapplication.

Nickel Boron (NiBo)Nickel Boron performs very well in hightemperature, high pressure applications withabrasive media and dry gases. It is resistantto damage from erosion, cavitation andthermal shocks and is ideal for steam service,catalyst handling and coal gasification. NiBohas limited corrosion resistance and is notrecommended for use with acids and dry orwet chlorine. NiBo coating is available onCF8M balls up to 16” size.

Tungsten Carbide (WC-Co)Tungsten Carbide is very resistant to wearfrom high cycle operations and erosion fromabrasive catalysts, muds and slurries. It isideal for cryogenic applications, oxygenservice and non-lubricative dry services.WC-Co is not suitable for use in corrosiveservices and condensates such as water, but generally performs well in hydrocarbongases and liquids. Maximum temperature islimited by the expansion characteristics ofthe base metal to the coating.

Tungsten Chromium Carbide[(W/Cr)C]Tungsten Chromium Carbide is the idealchoice for corrosive liquids at moderatetemperature. It provides excellent resistanceto wear and erosion in applications such asseawater, basics or organic acids, geothermalsteam and water, media with high chloridesand sour wet hydrocarbons containing H2S,sulphur and CO2. (W/Cr)C should only beused with liquid media.

Chromium Carbide (CrC)Chromium Carbide is well suited to veryhigh temperature gas or liquid applicationsand has excellent resistance to wear, erosionand corrosive media. It performs well in lowpressure steam service, coal liquefaction,catalyst handling and abrasive slurries. LowFriction version CrC-LF is applied to seatsurfaces to improve sliding performance.

Cobalt Based AlloyMetso utilizes multiple coating materialsclassified as cobalt based hard facings.Examples include Stellite, Alloy 12, Alloy50Nb and Celsit. Specific materials in thisclass are applied based on their individualproperties and suitability for use on differenttypes of parts such as seats, shafts andbearings. Physical properties shown aboveare representative of our most commoncobalt based alloy seat coating.

Borofuse Thermal DiffusionProcessBorofuse is a proces in which boron isdiffused into the surface of the base materialand can be applied to many ferrous, nickeland cobalt alloys and carbides. Wear anderosion resistance is greatly increased whilecorrosion resistance is retained or improved.It is well suited to high temperature andabrasive applications and services withdemanding material requirements andcorrosion concerns. There is no adhesivedivision point between the surface borideand substrate, resulting in excellentresistance to impact and thermal shocks.

Nitriding Thermal DiffusionProcessNitriding is a process in which nitrogenatoms are diffused into the surface of ferrousmetals like stainless steels, alloys, ormertensitic stainless steels. The nitrogenatoms attach to the chromium, iron, andother alloying elements, which then formhard nitride compounds. The hard nitridedsurface is useful in extending the life of avalve in high temperature and abrasiveapplications.

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Physical Properties of Coating Materials

Coating Description Thickness, mm Hardness, HRC/HV Application Process Suitable Substrates

HCr Hard Chromium 0.05 - 0.1 70 / 1000 Electroplated Stainless steels, nickel base alloys

ENP Electroless Nickel Plating 0.06 min 68 / 950 Electroplated Carbon and stainless steels, nickel base alloys

NiBo Nickel Boron 0.5 - 1.0 55 / 600 S&F CF8M, AISI 316 stainless steel

WC-Co Tungsten Carbide 0.1 - 0.15 70 / 1000 HVOF Stainless steels, nickel base alloys

(W/Cr)C Tungsten Chromium Carbide 0.1 - 0.15 70 / 1000 HVOF Stainless steels, nickel base alloys

CrC Chromium Carbide 0.1 - 0.15 65 / 800 HVOF Stainless steels, nickel base alloys

Cobalt Based Alloy 1.0 - 3.0 46 / 480 PTA Stainless steels, nickel base alloys

Borofuse Thermal Diffusion Process

Nitriding Thermal Diffusion Process

Recommended Trim Coating Combinations

Ball Seat Temperature Temperature Corrosion Erosion Liquid Media Dry Gas CostRange, °F Range, °C Resistance Resistance

HCr Cobalt based alloy -58 to 842 -50 to 450 Good Better Yes No $

ENP Cobalt based alloy -58 to 842 -50 to 450 Best Good Yes No $

NiBo Cobalt based alloy -328 to 1112 -200 to 600 Good Best Yes Yes $$$

NiBo CrC-LF (Low Friction) -328 to 1112 -200 to 600 Good Best Yes Yes $$$$

WC-Co WC-Co -328 to 842 -200 to 450 Better Better No Yes $$$$

(W/Cr)C (W/Cr)C -58 to 572 -50 to 300 Best Good Yes No $$$$

CrC CrC-LF (Low Friction) -328 to 1472 -200 to 800 Better Best Yes Yes $$$

Coating Materials

Properties and Recommendations

Photos courtesy of Deloro Stellite Group

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Series M2

Model Code Example Sizes ASME classes Ball Materials Seat Materials Availability

M2CA04AP 1" to 12" 150 / 300 CF8M / HCr SS + Cobalt based alloy Standard

Standard offering for M2 series with HCr / Cobalt based alloy trim coating combination is widely used in pulp and paper applications and many other services with moderate tem-perature requirements.

M2CA04YP 1" to 12" 150 / 300 CG8M / ENP SS + Cobalt based alloy Optional

Y = CG8M body and CG8M+ENP ball. Selected for services with pH<2. Seats are CG8M (317SS) base material with Cobalt based alloy coating.

Series XA, XT, XC, XB & XU


XA02DWTAJ2SJHADA 1" to 8" 150 / 300 CF8M / HCr SS + Cobalt based alloy Standard

Standard offering for a wide range of services consisting of clean liquids or gases with moderate corrosion requirements.

XA02DWTAS6SLHADD 1" to 8" 150 / 300 CF8M / NiBo SS + Cobalt based alloy Standard

Standard offering recommended for applications with higher pressure and temperature.

XA02DWTUS6SLJBDD 1" to 8" 150 / 300 CF8M / NiBo SS + CrC-LF Optional

Recommended for solids proof applications such as catalyst handling with J-seated valve construction.

XA02DWTKS6RRHRDD 1" to 8" 150 / 300 CF8M / WC-Co SS + WC-Co Optional

Recommended for cryogenic applications (cryo construction shown) and dry non-lubricative gas service.

XA02DWTAU3UCHDAD 1" to 8" 150 / 300 Duplex 5A / (W/Cr)C UNS S32750 / (W/Cr)C Optional

For corrosive liquid applications such as seawater, choice of base materials must be considered. In this example Duplex 5A is selected for the body and trim.

XA02DWTAS6RXHBDD 1" to 8" 150 / 300 CF8M / CrC SS + CrC-LF Optional

Recommended for gas or liquid applications with very high temperature.

XU__F 1" to 4" 600 See XA material combinations examples

Series S6 & S5


S60100FALAR1SLKGGB 1/2" to 12" 600 to 4500 316SS / NiBo SS / Cobalt based alloy Standard

Recommended for clean liquids or gases and services at high temperature and pressure.

S60100FALAR1SWHCGB 1/2" to 12" 600 to 4500 410SS / CrC 410SS / CrC Standard

Recommended for gas or liquid applications with very high temperature.

S60100FALAW2YYYYYA 1/2" to 12" 600 to 4500 410SS + Borofuse Stellite + Borofuse Optional

YY1 = Ball material 410SS + Borofuse treatment and 410SS stem. YYY2 = Solid stellite + Borofuse "X" style seats and graphite seals. Recommended for highly abrasive services.

Valve Application Examples

Seat Supported Ball Valves

These tables offer a small representation of various construction and coating combinations. Please contact the factory for recommendation on specific appli-cations.

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Series XG & XM


XG10DWTAJ2SJHADF 2" to 16" 150 / 300 CF8M / HCr Avesta / Cobalt based alloy Standard


XG10DWTAS6SLHADD 2" to 16" 150 / 300 CF8M / NiBo Avesta / Cobalt based alloy Standard

Standard offering for applications with higher pressure and temperature.

XG10DWTAJ2RRBRDF 2" to 16" 150 / 300 CF8M / WC-Co SS + WC-Co Optional

Recommended for solids proof applications such as catalyst handling.

XG10DWTAS6RRLRTD 2" to 16" 150 / 300 CF8M / WC-Co SS + WC-Co Optional

Recommended for polymer applications such polypropylene and polyethylene.

Series D2C, D2D & D1F


D2DA12DAS02 4" to 36" 150 / 300 CF8M / HCr SS + Cobalt based alloy Standard


D2DH12AAH03 4" to 36" 150 / 300 CF8M / HCr SS + Cobalt based alloy Standard

Standard high temperature offering for clean liquids and gases.

D2DH12ADH03 4" to 16" 150 / 300 CF8M / NiBo SS + Cobalt based alloy Standard

Recommended for higher temperature applications containing abrasives.

D2DC12AR1C103 4" to 36" 150 / 300 CF8M / WC-Co SS + WC-Co Optional

Recommended for cryogenic applications (cryo construction shown) and dry non-lubricative gas service.

D2DH24AR3Y03 4" to 36" 150 / 300 CF8M / CrC SS + CrC-LF Optional

Y = K3 seats with all graphite seals. Recommended for very high temp gas or liquid solids proof applications.

D1F 2" to 24" 600 See D2D material combinations examples

Valve Application Examples

Trunnion Mounted Ball Valves.

These tables offer a small representation of various construction and coating combinations. Please contact the factory for recommendation on specific appli-cations.

Photo courtesy of Deloro Stellite Group

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Metso Automation Inc., Tulppatie 1, P.O. Box 310, FI-00811 Helsinki, Finland, tel. +358 20 483 150, fax +358 20 483 151,www.metso.com/automation

Corporate OfficeLevytie 6, P.O. Box 31000811 HelsinkiFinlandTel. +358 20 483 150, fax +358 20 483 151

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For further information please contact one of our regional offices or visit our web site www.metso.com/automation

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