Microstructure and Properties of Nickel-Based Gradient Coatings Prepared Using Cold Spraying Combined with Laser...

Area of Science:

• Materials Science
• Surface Engineering
• Mechanical Engineering

Background:

• Copper substrates often suffer from poor wear resistance and susceptibility to thermal expansion mismatch in coatings.
• Traditional laser cladding gradient coatings (LGC) face challenges with high substrate reflectivity and CTE differences, leading to defects.

Purpose of the Study:

• To develop a crack-free, high-performance gradient coating on a copper substrate.
• To investigate the effects of a combined cold spray-laser cladding approach on coating properties and wear resistance.

Main Methods:

• Formation of a cold spray-laser cladding composite gradient coating (CLGC) on a copper substrate.
• Utilizing a Ni-Cu alloy intermediate layer to mitigate copper's high reflectivity and CTE mismatch.
• Characterization of coating microstructure, microhardness, friction, and wear behavior.

Main Results:

• CLGC formation without cracks or defects, improving cladding quality.
• Significantly increased microhardness (approx. 8 times Cu substrate) due to uniform hard phases (Ni₁₁Si₁₂, Mo₅Si₃).
• Reduced friction coefficient (0.28) and wear rate (one-third of Cu substrate), indicating excellent anti-wear properties.

Conclusions:

• The CLGC approach effectively overcomes limitations of traditional LGC on copper substrates.
• The developed coating exhibits superior hardness, reduced friction, and enhanced wear resistance.
• This method improves the usability of copper substrates in demanding applications.