Microstructural changes and dry sliding wear behavior of Cu-15Ni-8Sn-0.5Co alloy during deformation and aging treatment

The microstructural evolution and dry friction wear performance of the Cu-15Ni-8Sn-0.5Co alloy during deformation and aging treatment were studied using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and three-dimensional surface profilometry. The results show that the peak hardness of the Cu-15Ni-8Sn-0.5Co alloy initially increases and then decreases with increasing cold deformation, reaching a maximum hardness of 440 HV at 70 % cold deformation. During the aging process at 400 celcius, the phase transformation sequence of the Cu-15Ni-8Sn-0.5Co alloy with 70 % cold deformation is as follows: modulated structure - D022 ordered phase - gamma-D03 phase. The rapid formation of the D022 ordered phase, which is coherently dispersed within the matrix, is the main reason for the significant improvement in the mechanical properties of the alloy. However, the rapid nucleation and growth of the discontinuous precipitation structure are responsible for the reduced mechanical performance and limited resistance to over-aging in the alloy. Additionally, it also causes decreased friction and wear resistance in the alloy with 70 % cold deformation. At a load of 20 N, the primary wear mechanism of the peak-aged Cu-15Ni-8Sn-0.5Co alloy with 70 % cold deformation is abrasive wear. As the load increased to 120 N, the wear mechanism shifted to a combination of abrasive wear and fatigue spalling wear in the alloy.