Thermal Sprays

 

Tungsten Carbide

Tungsten Carbide coatings offer significant hardness, wear and corrosion resistance. The coatings are done through High-Velocity Oxygen Fuel spraying (HVOF) by using a combustive thermal spray at high velocity to develop a wear and corrosion-resistant coating. This results in a very dense, very adhesive and cohesive tungsten carbide coating, with comparatively very high bond strength, low residual stress, low porosity (typically less than 0.5%), and high wear and corrosion resistance. This offers excellent corrosion resistance except in high pH environments and in hydrofluoric acid solutions.

Benefits:

  • High wear and corrosion resistance
  • Resistance to sliding wear, abrasion, cavitations, and erosion
  • Good fatigue and impact resistance

 

Monel Alloy

Monel is a nickel-copper alloy (about 67% Ni – 23% Cu) which exhibits excellent corrosion resistance. Generally, its corrosion resistance is very good in reducing environments, but poor in oxidizing conditions. It is not useful in oxidizing acids, such as nitric acid and nitrous. Nevertheless, it is resistant to most alkalis, salts, waters, food products, organic substances and atmospheric conditions at normal and elevated temperatures. This nickel alloy is attacked in sulfur-bearing gases above approximately 700° F and molten sulfur attacks the alloy at temperatures over approximately 500° F. Monel 400 offers about the same corrosion resistance as nickel but with higher maximum working pressures and temperatures and at a lower cost due to its superior ability to be machined.

Benefits:

  • Resistant to sea water and steam at high temperatures, salt & caustic solutions
  • Good weld ability at high strength
  • Low corrosion rate in rapidly flowing brackish or seawater
  • Excellent resistance to stress-corrosion cracking in most freshwater
  • Resistant to a variety of corrosive conditions led to its wide use in marine applications & other non-oxidizing chloride solutions
  • Particularly resistant to hydrochloric and hydrofluoric acids when de-aerated.
  • Excellent resistance to neutral and alkaline salt.
  • Resistance to chloride induced stress corrosion cracking.
  • Good mechanical properties from sub-zero temperatures up to 1020° F.
  • High resistance to alkalis.
  • Virtually immune to chloride ion stress corrosion cracking in typical environments.

 

Not suitable for:

  • Nitric acid and ammonia systems
  • Offers some resistance to hydrochloric and sulfuric acids at modest temperatures and concentrations

 

 

Hastelloy

A nickel-molybdenum-chromium superalloy with an addition of tungsten designed to have excellent corrosion resistance in a wide range of severe environments. The high nickel and molybdenum contents make the nickel steel alloy especially resistant to pitting and crevice corrosion in reducing environments while chromium conveys resistance to oxidizing media. The low carbon content minimizes carbide precipitation during welding to maintain corrosion resistance in as-welded structures. This nickel alloy is resistant to the formation of grain boundary precipitates in the weld heat-affected zone, thus making it suitable for most chemical process application in an as welded condition.

Hastelloy is known as the most universally corrosion resistant material available today. It is used in a variety of environments from moderately oxidizing to strong reducing conditions. While hastelloy has exceptional resistance to sulfuric acid and hydrochloric acid, acid chlorides, solvents, formic and acetic acids, acetic anhydride, wet chloride gas, hypochlorites and chlorine solutions, it also has excellent resistance to phosphoric acid at all temperatures below boiling and at concentrations lower than 65%.

Hastelloy also exhibits excellent resistance to corrosion by seawater especially under crevice conditions. The limiting factor when dealing with strong oxidizing environments is the low Cr content, which means that hot, concentrated nitric acid environments are NOT desirable.

Benefits of Hastelloy Coatings:

  • Excellent corrosion resistance in reducing environments.
  • Exceptional resistance to strong solutions of oxidizing salts, such as ferric and cupric chlorides.
  • High nickel and molybdenum contents providing good corrosion resistance in reducing environments.
  • One of the few materials to withstand corrosive effects of wet chlorine gas, hypochlorite and chlorine dioxide.

Typical Applications of Hastelloy Coatings:

  • Impeller blades and housing of pumps
  • Pump sleeves and fittings
  • Sulfuric acid-handling equipment
  • Pulp and paper production
  • Sour gas wells
  • Waste treatment

 

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