Tribological properties of NiAl produced by pressure-assisted combustion synthesis

In this study, aluminum powder with 15 μm size and carbonyl-nickel powder with 4–7 μm size having 99% and 99.8% purity, respectively were used in order to produce NiAl by volume combustion synthesis. The production of intermetallic compound was carried out in an electrical resistance furnace in open air under a uniaxial pressure of 150 MPa at 1050 °C for 1 h. The formation temperature of NiAl intermetallic compound was determined to be 655 °C by differential scanning calorimeter (DSC) analysis. The presence of NiAl was confirmed by X-ray diffraction (XRD) analysis. Optical and scanning electron microscope (SEM) analysis revealed that NiAl phase has very low porosity. The relative density of the samples measured according to based on Archimedes principle was 99.6%. The microhardness of the samples measured by Vickers indenter was approximately 367 ± 17 HV1.0. The effect of load on wear rate in the case of using Al2O3 ball as a counterface material was also investigated using a ball-on-disc test method. The coefficient of friction for NiAl intermetallic compound run under 2 N load was calculated as 0.73 while it was 0.53 run under 10 N load. Depending on load, the wear rate of NiAl sliding against alumina ball was 0.016 mm3/N m for 2 N, 0.017 mm3/N m for 5 N and 0.009 mm3/N m for 10 N, respectively. The distribution of alloying elements within intermetallic compound was determined by energy-dispersive X-ray spectroscopy (EDS).