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Abstract <p>NiMoAl-Ag coatings enriched with h-BN are emerging self-lubricating systems that would provide desirable self-lubrication in tribo pairs and help in the continuous lessening of friction coefficient and wear. Despite demonstrated benefits of Ag and h-BN in reducing friction and wear in metal matrix coatings, the optimal h-BN concentration for balancing lubrication and coating integrity remained unclear. We hypothesized that a moderate addition of h-BN would significantly lower friction and wear by promoting stable tribo-layer formation without compromising bond strength. Four variants, NiMoAl-Ag (NAB0), NiMoAl-Ag-h-BN (3 wt%) (NAB3), NiMoAl-Ag-h-BN (7 wt%) (NAB7), and NiMoAl-Ag-h-BN (12 wt%) (NAB12) coatings, were produced via atmospheric plasma-spray (APS) and tested at 5, 10, 15, and 20 N using a rotary tribometer at room temperature (RT), @ 25&#xa0;°C. The micro-hardness values of the developed coatings decreased with rising h-BN content; nevertheless, NAB7 exhibited the best tribological performance. The coefficient of friction reduced from 0.49 at 5 N to 0.40 at 15 N, and wear was significantly lower than NAB0, attributed to sustained lubricious tribo-layers containing NiO, MoO<sub>3</sub>, NiMoO<sub>4</sub>, AgO, and AgMoxOy. The optimal content of h-BN in the derived coating (NAB7) has maintained a balance in between the lubrication support delivered by the h-BN and bond strength of the coatings, which played a pivotal role in continuous lowering of COF and increased wear resistance of the coatings.</p> Highlights <p>• NiMoAl-Ag-based composite coatings with varying h-BN content were developed via atmospheric plasma spray route.</p> <p>• Tribological behavior of the coatings was performed using a rotary tribometer under different loads at RT.</p> <p>• Micro-hardness values of the coated samples reduced as the concentration of h-BN increased in the coatings.</p> <p>• The formulated coating (NAB7) has shown the improved tribological behavior due to optimal (7 wt%) addition of h-BN.</p> <p>• The improved lubrication has been credited to formation of sustainable tribo-layers over the worn track containing NiO, MoO<sub>3</sub>, NiMoO<sub>4</sub>, AgO, and AgMoxOy along with h-BN.</p>

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Synergistic effect of Ag and h-BN on the NiMoAl-Ag coating deposited via atmospheric plasma spray

  • 期刊论文

  • 发表日期：

    2025年9月2日

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  • Rohit Kumar Singh Gautam,
  • Vivek Mani Tripathi,
  • Jitendra kumar Gautam,
  • Subhash Mishra,
  • Saood Ali

摘要

Abstract

NiMoAl-Ag coatings enriched with h-BN are emerging self-lubricating systems that would provide desirable self-lubrication in tribo pairs and help in the continuous lessening of friction coefficient and wear. Despite demonstrated benefits of Ag and h-BN in reducing friction and wear in metal matrix coatings, the optimal h-BN concentration for balancing lubrication and coating integrity remained unclear. We hypothesized that a moderate addition of h-BN would significantly lower friction and wear by promoting stable tribo-layer formation without compromising bond strength. Four variants, NiMoAl-Ag (NAB0), NiMoAl-Ag-h-BN (3 wt%) (NAB3), NiMoAl-Ag-h-BN (7 wt%) (NAB7), and NiMoAl-Ag-h-BN (12 wt%) (NAB12) coatings, were produced via atmospheric plasma-spray (APS) and tested at 5, 10, 15, and 20 N using a rotary tribometer at room temperature (RT), @ 25 °C. The micro-hardness values of the developed coatings decreased with rising h-BN content; nevertheless, NAB7 exhibited the best tribological performance. The coefficient of friction reduced from 0.49 at 5 N to 0.40 at 15 N, and wear was significantly lower than NAB0, attributed to sustained lubricious tribo-layers containing NiO, MoO3, NiMoO4, AgO, and AgMoxOy. The optimal content of h-BN in the derived coating (NAB7) has maintained a balance in between the lubrication support delivered by the h-BN and bond strength of the coatings, which played a pivotal role in continuous lowering of COF and increased wear resistance of the coatings.

Highlights

• NiMoAl-Ag-based composite coatings with varying h-BN content were developed via atmospheric plasma spray route.

• Tribological behavior of the coatings was performed using a rotary tribometer under different loads at RT.

• Micro-hardness values of the coated samples reduced as the concentration of h-BN increased in the coatings.

• The formulated coating (NAB7) has shown the improved tribological behavior due to optimal (7 wt%) addition of h-BN.

• The improved lubrication has been credited to formation of sustainable tribo-layers over the worn track containing NiO, MoO3, NiMoO4, AgO, and AgMoxOy along with h-BN.