Microstructure and wear resistance of laser cladding (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)B12 high-entropy ceramic composite coatings on 304 stainless steel

To address the limitations of 304 stainless steel (304 SS) in advanced applications due to its low hardness and poor wear resistance, (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Lu 0.2 )B 12 (REB 12 ) high-entropy ceramic composite coatings were prepared on the surface of 304 SS by laser cladding. The REB 12 powder was used as a laser cladding material, which is a high-entropy dodecaboride (HEDB) ceramic material with low density and high hardness, and possesses promising applications in the field of wear resistance. The phase composition, microstructure, elemental composition, microhardness and wear resistance of the REB 12 composite coatings were investigated under various processing parameters (2500w 10 mm/s, 3500w 10 mm/s and 2500w 7.5 mm/s). With the increase in laser energy density, the formation location of REB 12 high-entropy rare earth borides transitions from within the 304 SS substrate to the grain boundaries. The microstructure of the REB 12 composite coatings transitions from columnar dendritic to equiaxed grains and equiaxed dendritic. The average microhardness across the cross-section of the three REB 12 composite coatings was tested to be 1277 HV 0.2 , 958 HV 0.2 and 754 HV 0.2 , respectively, representing an enhancement of 5.6, 4.2 and 3.3 times compared to the 304 SS substrate. The wear rates of the coatings 1–3 were determined to be 2.25 × 10 −6 , 2.93 × 10 −6 and 3.23 × 10 −6 g N −1 ·min −1 , leading to respective reductions of 79.85 %, 73.76 % and 71.08 % compared to the 304 SS substrate (11.17 × 10 −6 g N −1 ·min −1 ). This study reveals that REB 12 composite coatings, fabricated using REB 12 powder as the cladding material by laser cladding, exhibit high microhardness and wear resistance, presenting a novel alternative for cladding materials.