High temperature tribological properties of NiCrBSiCFe plasma-sprayed coating on austenitic stainless steel substrate

In this study, the microstructural features, mechanical properties and dry sliding wear characteristics of NiCrBSiCFe plasma-sprayed on AISI 316 austenitic stainless steel (ASS) substrate were investigated. The coatings obtained were defect-free and metallurgically bonded to the substrate. Wear tests were carried out at 1 m/s sliding velocity under the load of 20 N for 2000 m sliding distance at various atmospheric conditions like room temperature, 150, 250 and 350 oC using a EN-8 medium carbon steel pin as a counterface material. The properties namely coating density, microhardness, coefficient of friction (CoF), wear resistance of the plasma-sprayed coating were studied. NiCrBSiCFe plasma-spray coated steel substrate showed superior wear resistance properties than the uncoated steel substrate in all the temperatures. The average wear resistance values of uncoated and NiCrBSiCFe coated material are 129 and 540 m/mm3, respectively. Thereby, the sliding wear resistance was improved up to four times more than that of the uncoated material. In wear test carried out at 350 oC, the coated substrates showed relatively lesser wear than in other temperatures due to the iron and chromium oxide formation, which acted as a protective layer. This was evident from X-ray diffraction studies (XRD). In addition, the shallow ploughing mode of wear reduced the severity of material removal at 350 oC. Using scanning electron microscope (SEM) pictures, the wear properties of the coated steel substrate were evaluated in terms of plastic deformation, material transfer and abrasion.