Effect of B Element on Tribological Properties of Laser Cladded AlCoCrFeNiTi High Entropy Alloy Coating

Abstract

For enhancing the protective effect of high entropy alloy coatings on steel components and exploring the strengthening effect of non-metallic element boron, the AlCoCrFeNiTiBx coatings were prepared using laser cladding technology, and the effect of different B contents on the microstructure and tribological properties of coatings was investigated via various instruments such as X-ray diffractometer(XRD), scanning electron microscopy(SEM), microhardness tester and multifunctional friction testing machine. Results showed that the crystal structure of the AlCoCrFeNiTiBx(x=0.05, 0.10, 0.30) high entropy alloy(HEA) coating mainly consisted of BCC and FCC phases. As the B content increased, the BCC phase proportion rose, and the lattice distortion intensified. The average hardness of the coating surface increased initially and then decreased with the increase of B content. Remarkably, the average friction coefficient and wear rate of the HEA coating at three different loads(10, 20 and 30 N) were significantly lower than those of the GCr15 alloy. Moreover, as the load increased, the friction coefficient of the HEA coatings demonstrated a decreasing trend. The addition of element B was beneficial for reducing the friction coefficient and wear rate of HEA coatings. The AlCoCrFeNiTiB0.1 HEA coating had the lowest average friction coefficient and wear rate, with a decrease of about 20.4% in average friction coefficient and a decrease of about 95.9% in wear rate compared to GCr15 under a load of 20 N. The main wear form of HEA coating was layer by layer peeling controlled by plastic deformation. In summary, the addition of element B not only improved the hardness of the coating, but also promoted the formation of oxide film, thereby reducing the friction coefficient and wear rate of HEA coating.

Keywords

• high entropy alloy；laser cladding；tribological properties；micro - alloying