Eco-friendly Ni-W Alloy Coatings with Multilayer Architecture Improve Service Life of Machine Parts

Moving machine parts, such as gears in automobiles, often suffer from significant energy loss and failure due to high friction, which leads to wear and tear.

Researchers at the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), an autonomous institution under India’s Department of Science & Technology (DST), have developed a groundbreaking, eco-friendly pulsed electrodeposition process to create Ni-W (Nickel-Tungsten) alloy coatings with a unique multilayered architecture. This new technique promises to mitigate friction, reduce energy loss, and enhance the durability of moving machine parts such as gears, a crucial innovation for industries ranging from automotive to heavy machinery.

Moving machine parts, such as gears in automobiles, often suffer from significant energy loss and failure due to high friction, which leads to wear and tear. This problem is commonly addressed through surface coatings or oxide layers that reduce direct contact between moving parts. However, heat generated during sliding wear contacts leads to the formation and eventual removal of oxide layers, a cyclical process that impacts the service life of components. Researchers have long sought coatings that can efficiently dissipate frictional heat, thus reducing wear and increasing component longevity.

A thinner, well-adhered oxide layer that efficiently dissipates heat is crucial for achieving a low wear rate and extending the life of machine components. To address this, researchers are exploring multilayer coatings with alternating layers of materials with different thermal properties, which can better manage heat and wear.

Eco-friendly Pulled Electrodeposition for Multilayer Coatings

The innovative Ni-W alloy coating process developed by Dr. Nitin P. Wasekar and his team uses an eco-friendly pulsed electrodeposition technique to deposit the Ni-W alloy coatings in a multilayered structure. The electrolyte used for this process contains both nickel (Ni) and tungsten (W) ions, which are co-deposited onto the surface of the component under pulsed currents. By adjusting the pulse currents in both forward and reverse modes, the concentrations of Ni and W can be controlled within the coatings, leading to the formation of alternating layers with varying amounts of tungsten.

This multilayered structure consists of nanocrystalline layers with a higher tungsten content (lower thermal diffusivity) alternating with microcrystalline layers containing lower tungsten levels (higher thermal diffusivity). This configuration is carefully crafted to optimize heat dissipation and reduce residual stress, thereby improving the mechanical properties and wear resistance of the coated components.

Innovative Benefits: Reduced Stress and Wear Rate

One of the standout features of this new coating process is that it employs a single electrolyte for the deposition of multilayer coatings, making the technique simpler and more industrially feasible. The pulsed electrodeposition approach creates coatings with remarkable mechanical properties, including reduced residual stress and enhanced toughness. The multilayer structure's waviness helps minimize residual stress by up to 80-90% when compared to monolithic (single-layer) Ni-W coatings or conventional hard chrome (HCr) coatings, despite having similar hardness ranges.

Tests on the wear resistance of the multilayered Ni-W coatings have demonstrated impressive results. The wear rate of these coatings, with individual layer thicknesses as thin as 100 nm, was found to be approximately half that of monolithic Ni-W coatings and about one-third that of conventional hard chrome coatings. This substantial reduction in wear rate is attributed to a decrease in the coefficient of friction, facilitated by the formation of a thin, adherent WO3 (tungsten oxide) tribo-film on the coating’s surface during operation.

Effective Heat Dissipation through Multilayered Architecture

The multilayered architecture of the Ni-W coatings not only enhances mechanical strength but also plays a critical role in heat management. The heat generated at the interface during frictional contact is efficiently managed by the different thermal diffusivities of the layers. The higher tungsten layers (with lower thermal diffusivity) generate more heat, but this is counteracted by the adjacent lower tungsten content layers, which dissipate the heat more effectively. This balance between the layers results in superior heat dissipation, contributing to lower friction and extended service life of the components.

Industrial Applications and Future Potential

This novel Ni-W multilayered coating technique has vast potential for a wide range of industrial applications, particularly in components that are subjected to high friction and wear, such as gears, automotive parts, and machinery. The ability to reduce friction and wear while enhancing the toughness and durability of moving machine parts can lead to significant energy savings and longer service lives for critical industrial equipment.

Furthermore, the process’s eco-friendly nature, relying on pulsed electrodeposition and a single electrolyte, makes it a highly sustainable alternative to conventional coating techniques, which often involve more complex and hazardous processes.

The development of these eco-friendly Ni-W alloy coatings with a multilayer architecture marks a significant step forward in addressing the challenges of friction, wear, and heat dissipation in moving machine components. By improving mechanical properties and reducing energy loss, this innovation holds the potential to revolutionize industries ranging from automotive to heavy machinery, providing long-term solutions for enhancing the performance and longevity of critical components. The integration of this technology into industrial applications could lead to more sustainable, efficient, and durable machinery worldwide.