Amorphous

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Amorphous Metallic Glass Iron-Based Coatings

  • There is an increasing demand to replace Co-based coatings with cheap and environment friendly Fe-based coatings in corrosive environments.
  • Very interesting work was carried out at MDPI where two Fe-based and 1-Co-based were product by the high velocity Air fuel spraying. The corrosion behaviour was thoroughly studied (3-5 wt. % Nacl solution).
  • Fe- alloyed coatings slowed down the corrosion process considerably.
  • Increasingly the in-flight temperature led to a denser coating with fewer defects which seemed to improve the corrosion resistance and can be recommended as a potential alternative to Co-based coatings.
  • Iron Based powders having the shield of Endurance effect. This can resist corrosion in concentrated salts seawater environment.
  • The coating can be grindable by silicon carbide wheels.
  • This coating is the best alternative for non-friendly electrolytic, chrome plating.

Amorphous Metallic Glass Feedstock Composition

Nominal Composition Wt.%
Chromium <25%
Molybdenum <20%
Tugsten <10%
Boron <5%
Manganese <5%
cabon <3%
Silicon <2%
Iorn Balance

Properties

Feature S.I Units
Apparent metal logographic prosity <1.0%
Bond strength to carbon steel 70+MPa@500um Thk.
Hardness 65HRC
Max.coating Thk.(as-sprayed) 1mm
Max.working Temp. 700°C
amorphous iron-based coating

Micrograph of Amorphous Metallic Glass Coating

Typical Applications of Iron-Based Coatings

  • Hydraulic rods
  • Boiler tubes
  • Down hole oil drilling tools
  • Pump components: impellers, casings, shafts
  • HVOF thermal spraying is one of the most widely used process for depositing coatings such as metals, cermet’s, ceramics, and metallic glasses, which seems more feasible due to its high cooling rates of 107 – 1010 K/s. however, in comparison with the HVOF process, HVAF system which combusts a mixture of compressed air and fuel gas in the combustion chamber has a lower spraying temperature (1600k) than HVOF (1900k) process. So, the chemical uniformity by controlled by controlled oxidation in the coating by hvaf can be improved. Moreover, the high particle velocity, typically over 700 m/s, of the hvaf process has been reported to provide lower porosity in the coating and well adhesion strength than HVOF. Furthermore, the use of air instead of oxygen for combustion by hvaf is expected to lower the cost of the spraying and promote its competitiveness over other processes.
  • Fe- based metallic glass coatings deposited by ac-hvaf have much better corrosion than stainless steel, which is mainly dependent on their amorphous structure and chemical composition; both of amorphous coating and stainless steel have the Cr element, which is the element of self- passivation. For amorphous coating, the introduction of Cr element contributes to the formation of a strong passive film of hydrated chromium oxy- hydroxide. This process effectively inhibits the active dissolution of the amorphous phase and enhances the corrosion resistance.

Endurance Wear Solutions Llp thermal spray HVAF amorphous metallic glass coatings at our spray shop in Mumbai, Maharashtra, India. Call us or send an inquiry to get our best price.

References….

  • Li L, Kharas B, Zhang H, Sampath S Suppression of crystallization during high velocity impact quenching of alumina droplets: observations and characterization. Mater SciEngA 2007:456:35-8.
  • He J, Ice M, Lavernia E particle melting behaviour during high- velocity oxygen fuel thermal spraying. J Therm spray Technol 2001:10:83-93.
  • Habazaki H, Kawashima A, Asami K, Hashimoto K. The effect of molybdenum on the corrosion behaviour of amorphous Fe-Cr-Mo-p-c alloys in hydrochloric acid. Mater SciEngA 1991:134:1033-6.
  • D.J. Branagan et.al.Wear and Corrosion Resistant Amorphous/Nanostructured Steel Coatings For Replacement of Electrolytic Hard Chromium

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