Investigations on the Influence of Annealing on Microstructure and Mechanical Properties of Electrodeposited Ni-Mo and Ni-Mo-W Alloy Coatings

Chao Zhang,Sichao Dai,Wudong Si,Yin Wang,Da Shu

doi:10.3390/coatings11111428

Chao Zhang, Sichao Dai + Show 3 more

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https://doi.org/10.3390/coatings11111428

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Abstract

Ni-Mo and Ni-Mo-W coatings were electrodeposited on a stainless steel sheet, and then were annealed at 200, 400, and 600 °C. The effect of annealing heat treatment on the microstructure of Ni-Mo and Ni-Mo-W electrodepositions, their nano-hardness, and tribological properties were investigated. It was revealed that the average crystalline are refined and phase separation are promoted with formation of Mo-W related intermetallic precipitates at temperature exceed 400 °C on account of the co-existence of Mo-W elements within Ni-Mo-W coatings. Annealing heat treatment leads to hardening, and the hardness and elastic module increase significantly. The grain boundary (GB) relaxation and hard precipitated intermetallic particles are responsible for the annealing-induced hardening for ≤400 °C annealed and 600 °C annealed Ni-Mo-W coatings, respectively. In addition, both adhesive wear and abrasive wear are observed for coatings, and abrasive wear becomes predominant when annealing temperature up to 600 °C. The wear resistance of coatings is improved eventually by formation of a mixture of lubricated oxides upon annealing at 600 °C and the enhancement of H/E ratio for ≤400 °C annealed Ni-Mo-W coatings.

Highlights

The processing of nanomaterials by electrodeposition is a conventional yet one of the most effective and low-cost bottom-up methods [1], e.g., electrodeposition of Ni-P [2,3], NiFe [4,5], Ni-W [6,7] and Ni-Mo [8,9] alloy coatings and their composite coatings
Some other studies showed that W additions in Ni coatings can refine the grain size of deposits, and the grain size reduces with the increment of W content, providing the improvement of the strength, thermal stability, corrosion and wear resistance with serving as several applications in the field of protective coatings and micro-electromechanical systems (MEMS) [10,11,12,13,14,15]
As reported of induced co-deposition principle of Ni-Mo-W coating [36], the electrodeposition process would be promoted with the increase of the concentration of Na2 WO4 ·2H2 O as the competition relation in the deposition process of Mo and W

Summary

Introduction

The processing of nanomaterials by electrodeposition is a conventional yet one of the most effective and low-cost bottom-up methods [1], e.g., electrodeposition of Ni-P [2,3], NiFe [4,5], Ni-W [6,7] and Ni-Mo [8,9] alloy coatings and their composite coatings. Ni-based metals resulting in an alloy exhibit superior mechanical and electrochemical properties. Mo as an alloying addition is the suitability of Ni alloy for hard chromium replacement, due to its high thermal stability, electrical and thermal conductivity amongst refractory metals and low thermal expansion coefficient [16,17,18]. The researchers reported that when the Mo content in the deposited Ni-Mo alloy coating exceeds 25 at.%, the coating is composed of amorphous phase and exhibits micro-cracks and pits, which reduce its mechanical properties at ambient and elevated temperature [19,20]. The content of Mo in Ni-based coating is adjusted in low level to avoid micro-cracks and pits. Some literatures reported that the addition of hard second phase particles such as ZrO2 [21], SiC-TiN [22], Al2 O3 [23] and diamond [24]

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