Effect of Diamond Surface Pretreatment and Content on the Microstructure and Mechanical and Oxidation Behaviour ofNiAl/Fe-Based Alloys

The effect of diamond surface pretreatment and content on the microstructure and mechanical properties of NiAl/Fe–xdiamond(x= 0, 5, 10, 15, and 20wt.%) alloys was investigated after mechanical alloying with subsequent hot-pressing sintering. The resultsshowed that after the surface pretreatment, a complete transition layer containing W existed on the outer surface of the diamondgrains, which improved the interfacial bonding strength of the diamond grains and NiAl/Fe matrix to an excellent level. As thediamond content increased, the compressive strength of the NiAl/Fe-based alloys declined, but the alloy with 10 wt.% diamondhad a higher value than that of the other NiAl/Fe-based alloys. Short cracks and transgranular fracture were observed in thefracture surface of all materials. For the material with 20 wt.% diamond, intergranular fracture was obvious, and many diamondparticles appeared along the fracture direction, which caused the compressive strength to be the lowest of the samplesconsidered in this study. After the addition of diamond, the oxidation resistance of NiAl/Fe-based alloys decreased due to aloose oxidation layer and diamond graphitization. The thermal conductivity of the alloyfirst increased and then decreased withincreasing diamond content. A NiAl/Fe-based alloy with 15 wt.% diamond demonstrated the maximum thermal conductivity of53.2 W/(m·k) at 600°C among the samples in this study