Effect Of ZrC On The Microstructure And Wear Resistance Of The Fe-Based Alloy Coatings By Plasma Transferred Arc Welding

The iron-based alloy with 0.0%,1.0%,3.0%,5.0% and 7.0%(in weight percentage)micro-ZrC or nano-ZrC coatings were deposited on Q235 steel by plasma spray welding process.Microstructure and phases composition of the coatings were investigated by means of optical microscope(OM),scanning electron microscope(SEM),EDS and X-ray diffraction instrument(XRD).The microhardness and wear resistance of the deposited coatings were tested using microhardness tester and pinon-disc wear tester,and the mechanism was studied as well.The Fe-based alloy was composed of ?-Fe,?-Fe and(Cr,Fe)7C3,and which unchanged by adding 1.0% micro-ZrC or nano-ZrC.The ?-Fe phase disappeared with addition of 3.0% ZrC.The ZrC phase and reappeared ?-Fe phase were identified by adding 7.0% micro-ZrC.While,there was no ?-Fe phase by adding 7.0% nano-ZrC in the spray welding layer.The developed columnar dendrites and laminar eutectic structure were observed on the Fe-based alloy coatings.The restrained dendrite and growth direction were observed by adding micro-ZrC or nano-ZrC.The refined microstructure was obtained with increasing mount of ZrC.The uniform and compact equiaxed dendrite appeared after adding 5.0% ZrC.This effect of nano-ZrC was more obvious than that of microZrC.However,the coarser microstructure was observed by adding 7.0% ZrC,and the dendrite reappeared in the coatings.The micro-ZrC or nano-ZrC had the similar effect on the microhardness and wear resistance of the coatings.With the micro-ZrC or nano-ZrC content increased,the microhardness and wear resistance were obviously improved.The hardness of the iron base coating without ZrC was 463.15 HV.With addition of 5.0% micro-ZrC or nano-ZrC,which were 815.95 HV and 851.15 HV,increased by 76.17% and 83.77%,respectively.The main wear mechanism of spray welding layer was fatigue peeling.The serious peeling and peeling phenomena appeared on the worn surface without ZrC addition.After the addition of ZrC,the flaking decreased and the abrasive wear was observed.The wear resistance of the coatings with nano-ZrC was slightly better than that of with micro-ZrC.When the added amount of nano-ZrC reached 7.0%,the wear rate of the coatings was only 4.5×10-14m3/Nm,which decreased by 85.1%.