Microstructure and Properties of the Tribaloy T-800 Coating Fabricated by Laser Cladding on the DZ125 Superalloy

To address the problem of wear and failure of the DZ125 superalloy turbine blades, a Tribaloy T-800 coating is fabricated on the DZ125 superalloy by laser cladding. The microstructure, phase composition, microhardness and wear resistance of the T-800 laser cladding coating are studied. The experimental results indicate that no cracks are detected within the coating, and a strong metallurgical bond between substrate and coating is observed. In addition, columnar crystals are formed in the bottom of the coating, while equiaxed crystals are formed in the middle and top of the coating. The T-800 laser cladding coating consists mainly of face-centered cubic α-Co solid solution and Co3Mo2Si hard phase. The shape of the Co3Mo2Si is granular and striped at the bottom of the coating, while the shape of the Co3Mo2Si in the middle as well as the top of the coating is striated and radiated. Moreover, the distribution density of Co3Mo2Si is highest in the middle of the coating compared to the top and bottom. The average microhardness of the T-800 laser cladding coating is approximately 535 HV0.5, which is 1.27 times that of the substrate. Furthermore, the average microhardness of the bottom, middle and top of the coating is 495 HV0.5, 569 HV0.5 and 537 HV0.5, respectively. The average coefficient of friction of the substrate is 0.6, and the wear mechanism of the substrate is abrasive wear, adhesive wear and oxidative wear. Compared to the substrate, the average coefficient of friction of the T-800 laser cladding coating is reduced by 42%. And, the wear mechanism of the T-800 laser cladding coating is slight abrasive wear, adhesive wear and oxidative wear.