Effects of TiB₂ Particles Content on Microstructure, Mechanical Properties and Tribological Properties of Ni-Based Composite Coatings Reinforced with TiB₂ Particles by Laser Cladding

• Main Authors: Binghui Tang, Yefa Tan, Ting Xu, Zhidan Sun, Xiaotun Li
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Coatings
• Subjects: composite coating; TiB₂ particles content; microstructure; tribological properties
• Online Access: https://www.mdpi.com/2079-6412/10/9/813

The effect of TiB₂ particles content (10–40 wt.%) on the microstructure, mechanical properties and tribological properties of TiB₂-reinforced Inconel 718 alloy composite coatings by laser cladding was investigated. From the perspective of solidification thermodynamics and dynamics, when the TiB₂ particles content increases from 10 to 30 wt.%, the cooling rate increases for the increase in thermal conductivity and thermal diffusion coefficient, leading to the decrease in dendrite size, and the uniformity of TiB₂ particles becomes better for the decrease in the critical capture speed of the solid–liquid interface, causing the improvement of microhardness and tribological properties. However, when the TiB₂ particles content is too high (40 wt.%), the cooling rate decreases for the increase in heat released by solidification, so the dendrite size increases, and the Marangoni convection is too weak to drive the rearrangement of TiB₂ particles, leading to the heterogeneous microstructure, large fluctuation of microhardness and the deterioration of tribological properties. When the TiB₂ particles content is 30 wt.%, the composite coating has the finest and densest dendrites and evenly distributed TiB₂ particles, the bonding strength is as high as 1.714 GPa, the microhardness is up to 844.33 HV_0.2, which is 2.98 times that of Inconel 718 alloy coating, and the friction coefficient and the wear rate are 0.355 and 9.12 × 10⁻⁷ g/(N·m), which are 22.99% and 83.86% lower than those of the Inconel 718 alloy coating.