Scientists Develop New Nickel Alloy Coating Method
The Government of India’s Department of Science and Technology (DST) announced earlier this week that researchers have developed a new technique to deposit nickel alloy coatings on high-performance materials, with the hopes of replacing environmentally toxic chrome coatings.
According to the release, the coatings obtained are also highly corrosion resistant. DST reports that the nano-crystalline coatings can also cater to the need for the replacement of hazardous chrome coatings.
Led by Dr. Nitin P. Wasekar, the research group from the Center for Engineered Coatings at the International Advanced Research Center for Powder Metallurgy & New Materials (ARCI) has developed a lab-scale process to deposit nanostructured nickel alloy coatings using pulsed electroplating.
Compared to conventional, direct current used for chrome plating, the scientists utilized electric current in the form of pulses of duration of a few milliseconds for electroplating purposes.
The process reportedly consists of environmentally friendly electrolyte consisting of nickel and tungsten ions that is the source of strengthening elemental tungsten (W) and nickel (Ni). The pulsed current is applied between the components to be coated, acting as cathode and non-consumable anode.
The pulsed current effect was then used for nano-crystalline coatings, where high instantaneous current density for very small duration reportedly resulted in high rate of nucleation. DST reports that, unlike in conventional direct current plating, the coatings were virtually porosity free, crack free with minimal hydrogen uptake, and exhibited high hardness (700-1200 HV) and wear resistance.
New technique of corrosion-resistant nickel alloy coatings can replace toxic chrome plating— PIB India (@PIB_India) January 10, 2023
The coatings obtained are also highly corrosion-resistant and useful for the plastic ware industry.
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The coating is reportedly extremely corrosion resistant, withstanding up to 700 hours of salt spray. It can also withstand temperatures up to 500 degrees Celsius (932 degrees Fahrenheit) without thermal softening, improving the life of die components by at least two times compared to conventional chrome plating.
“They were successfully applied to die-casting components used in plastic bottling industry, wherein the temperatures at the die interface can be over 280 C,” wrote the DST.
“With numerous applications in automotive, defense, and aerospace for these coatings, the process know-how is ready for transfer as a replacement for conventional chrome plating.”
Other Recent Coating Technology
In May, the DST revealed that scientists had developed a low-cost iron aluminide coating that can reportedly increase corrosion resistance in harsh environments, up to four times increased corrosion resistance than that of mild steel.
Currently, thermally sprayed coatings composed of thermally sprayed Chromium Carbide-Nickel Chromium Powder (Cr3C2-NiCr) and Tungsten Carbide-Cobalt (WC-Co) are used for their wear and high-temperature oxidation resistance applications. They reportedly provide hardness, toughness and better corrosion resistance under exposure to up to 550 degrees Celsius (1022 F) in the case of WC-Co coatings and up to 850 C for CrC-NiCr coatings.
However, these powders can be expensive, and chromium is toxic in its hexavalent state. Because of this, a team of researchers from the Center for Engineered Coatings (CEC) and ARCI stated that iron-based coatings are promising.
Iron-based solid phases involving two or more semimetallic elements, or intermetallics, can also provide hardness and better corrosion resistance. Their deployment, however, is reportedly restricted due to low ductility.
To address this, the scientists synthesized the iron-based intermetallic powders and utilized the same for depositing the coatings using detonation spray coating technique. ARCI reportedly developed gas atomized iron aluminide powder and deposited it on mild steel substrates with this method without any cracks or spalling.
Results showed that the coatings exhibited better corrosion resistance when chromium and aluminide are in a solid solution with iron than in the iron-rich phases. They also demonstrated increased wear resistance by 30% to 40% than mild steel.
These results imply that iron-aluminide coatings can be used for high-temperature erosion resistance applications, such as in thermal power plant turbine blades, aerospace engine blades, landing gear shafts or steel rolls in the paper industry.
More recently, in November, the DST also reported that a research team from the Indian Institute of Technology Madras has developed a new technology that can reportedly produce new-generation superabrasive tools for advanced grinding applications.
Benefits of these tools include meeting high productivity, energy efficient material removal requirements and enhanced tool life.
The superabrasive tools are produced using active brazing technology, with attributes of high crystal exposure above bond level. The DST reported that the joint strength and wear-resistant characteristics of bond are higher compared to commercial counterparts, with the tools withstanding more grinding force, offering higher tool life and executing load-free grinding of advanced materials with an extremely high material removal rate.
These versatile geometry tools can then reportedly be tailor-made to suit a variety of industries, such as aerospace, automobile, mining and dental surgery.
For the coating application, the team recommends utilizing application-specific-advanced coatings. The novel formulation reportedly offers an excellent blend of strength, wear resistance and wetting characteristics.
Then, the grit-planting, or placing of grits in pre-defined coordinate position on grinding wheel's working surface, setup allows a manufacturer to print grit in a customized pattern to suit the requirement of an application. The recommended coating then enhances the durability of the bond, adding life to the developed tools.