Mechanical and Tribological Performance of a Ni-Based Alloy Coating Deposited by Laser Directed Energy Deposition on Gray Cast Iron Substrate

Gray cast iron (GCI) is widely used in industries due to its cost-effectiveness and beneficial properties. This research aims to optimize the parameters for laser cladding (LC) to deposit Ni-1031 alloy coatings on GCI substrates, primarily sourced from large used diesel engine blocks. To achieve this, a design of experiments approach was utilized, assessing parameters such as laser power, travel speed, hatch spacing, and layer height while analyzing the microstructural characteristics through single beads, layers, and multilayer placements. The results indicated successful mitigation of metallurgical bonding issues and cracks at the interface due to refined dendritic grain structures. Notably, the hardness of the Ni-based coatings exceeded that of GCI, attributed to solid-solution strengthening and the presence of B and Cr-rich precipitates. Furthermore, tribological tests, specifically reciprocating ball-on-flat assessments, demonstrated superior performance of the GCI, primarily due to the effective lubrication provided by graphite, leading to lower friction coefficients and wear rates. These findings highlight the importance of material optimization and processing parameters in enhancing the properties of coatings applied to GCI substrates.