Effect of carbide degradation in a Ni-based hardfacing under abrasive and combined impact/abrasive conditions

摘要

Within this work, the effect of carbide degradation in a WC/W_2C reinforced Ni-based hardfacing was assessed under abrasive and combined impact/abrasive conditions. In view of the above, a WC/W_2C reinforced Ni-based hardfacing was deposited by plasma transferred arc (PTA) welding using different welding currents. Microstructure was characterised by quantitative metallography to determine specific structural parameters: mean carbide diameter and carbide area fraction. Scanning electron microscopy (SEM, EDS) and X-ray diffraction (XRD) were also used to characterise carbide dissolution mechanism. Tribological behaviour was determined with a 3-body abrasion test according to ASTM G65 and with a cyclic impact/abrasion test (CIAT). Results showed significant carbide degradation with increasing welding current, resulting in a significant reduced primary carbide content and carbide diameter. Reduced carbide content indicated a significantly wear rate increase under pure 3-body abrasion conditions. Specific wear energy was determined under pure abrasive condition and showed significant dependence on the primary carbide content. However, wear rates under combined impact/abrasion were at constant level due to the reduction of the brittle primary carbide content.