Improvement of impact wear properties of seat insert by laser cladding cobalt-based alloy

The impact wear properties of two different contact pairs, N80A valve-cast iron seat insert (cast iron group) and N80A valve-clad seat insert (cladding group), were studied in this work. In this paper, an independently designed tribo-tester combined with a depth gauge and corresponding auxiliary devices can record the axial subsidence of the contact pairs during the entire worn process. The results showed that during the 5 x 10(6) impact test, cast iron groups and cladding groups followed the worn process curve, and all went through the running-in stage and the stable worn stage. However, at each stage, the subsidence of cladding groups was smaller than that of cast iron groups. The roughness meter not only recorded the roughness of all samples before and after the test, but also can obtain the respective subsidence of the samples through the difference between the profiles before and after the test. The results can be mutually corroborated with the axial subsidence measured by the depth gauge. As a result, the roughness of the sealing surfaces of all valve-seat inserts increased significantly after the impact test. The total worn subsidence of the cast iron groups was about 1.61 times that of the cladding groups. The worn morphology was further studied by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The cast iron group mainly experienced serious adhesive wear and oxidation wear, while the cladding group mainly experienced fatigue wear, oxidative wear and abrasive wear.