Abstract
Surface tailoring with plasma transferred arc (PTA) hardfacing involves the deposition of powder mixtures to produce coatings with an almost unlimited chemical composition. PTA hardfacing is particularly important for processing low weldability alloys, such as those for high-temperature applications, of which NiCrAlC is an example. This study analyzed NiCrAlC coatings processed by PTA using a mixture of elemental powders. Deposition on AISI316L plates was carried out with currents of 100 A and 130 A to induce variations in the chemical composition of the coatings, which were also subjected to isothermal exposure at temperatures of up to 1000 ºC for up to 72 hours in an air furnace. The results show that the aluminide compounds were stable, the coatings that solidified more slowly having the highest hardness after temperature exposure and potentially being suitable for use in high-temperature abrasion environments.
Highlights
Intermetallic compounds have been extensively used to manufacture components operating at high service temperatures[1]
This study investigates the characterization of NiCrAlC coatings processed by plasma transferred arc (PTA) hardfacing before and after exposure to temperatures of up to 1000 °C and seeks to optimize the chemical composition of the deposited powder mixtures to achieve higher, more stable coating hardness after temperature exposure
These may be associated with the steeper temperature gradient between the coatings and substrate, causing the coatings to solidify faster and preventing them accommodating the thermal expansion cycling experienced by the substrate during heating and cooling[7]
Summary
Intermetallic compounds have been extensively used to manufacture components operating at high service temperatures[1]. The alloy was designed to offer good abrasion resistance at high temperature, a characteristic that is as a consequence of the intermetallic matrix of Ni3Al with a dispersion of hard chromium carbides. As-cast NiCrAlC alloy[3] and high velocity oxygen fuel (HVOF) thermal spray coatings[4] were tested for wear resistance and showed good wear performance at room temperature. Plasma transferred arc (PTA) hardfacing produces coatings that have a metallurgical bond with the substrate, and the processing parameters allow solidification rates to be controlled and defects typically found in thermal spray coatings and casting materials to be minimized. This study investigates the characterization of NiCrAlC coatings processed by PTA hardfacing before and after exposure to temperatures of up to 1000 °C and seeks to optimize the chemical composition of the deposited powder mixtures to achieve higher, more stable coating hardness after temperature exposure
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