Microstructure and tribological behaviour of FeCoCrNiAlCuMn particles alloyed on Inconel-718 substrate using plasma transferred arc technique

Abstract

Inconel-718 alloy (IN-718) is a nickel-based superalloy that has extensive applications in many industries such as power generation, gas turbine, tubing hangers, safety valves systems, aerospace, nuclear engineering, etc. However, noticeable wear occurs on the IN-718 structure, leading to reduction in service life and failure of components. In the present study, the ball-milled alloy powders FeCoCrNiAlCuMn were preplaced on the IN-718 substrate and the substrate was alloyed through Plasma Transferred Arc (PTA) process. Then, the thickness of the alloyed region, phase formation, microstructural changes, microhardness and influence of alloy powder on the tribological properties were analysed. Further, the mechanism involved during the wear test and surface roughness of worn-out specimens were studied. The result shows that the PTA alloyed region possesses different phases such as BCC, FCC and intermetallic compounds. The alloying elements were well mixed with the substrate material and good metallurgical bonding was formed. The microhardness of 883 HV0.2 was achieved in the alloyed region while the substrate showed 312 HV0.2. The alloyed specimen exhibited superior wear resistance compared to the substrate due to the higher binding force of alloying elements such as Fe, Co, Ni and Co, which restricted the material deformation during the wear test. Moreover, broadening of the BCC phase of the alloyed region and intermetallic phase increased the hardness of the alloyed region, resulting in the improvement of wear resistance. The oxide phases such as Al2O3, CuO, Cr2O3, NiO and FeO were formed in the alloyed region during the wear test due to the formation of frictional heat. These oxide layers acted as a lubricant film to protect the alloyed region as well as diminished the Coefficient of Friction (CoF).