Study On The Process And Mechanism Of WC-Co Wear-resistant Coating On The Surface Of Steel By Laser Cladding

A comprehensive study of the phases and microstructure evolution,microhardness and wear performance of WC-12Co as well asWC-25Co composite coatings fabricated on the surface of 304 stainless steel and high chromium cast iron by laser cladding using coaxial powder-feed mode is presented in this work.The main results are as follows:When three layers of WC-12Co composite powders were cladded on the surface of 304 stainless steel,the W and C on the edge of WC-12Co composite powders melt partially in liquid Co as well as 304 stainless steel matrix,and then new carbides consist of block WC,petal shaped Co3W3C and dendritic Fe3W3C were formed.The WC-12Co wear-resistant coating with no porosity,cracks and drawbacks like decarburization were obtained,showing high densification and good metallurgical bonding with the substrate at the laser power of 1500 W.It is worth noting that with the increase of laser power,the microhardness of the coatings increased first and then decreased,the highest microhardness of 1600 HV0.3 was obtained at laser power of 1500 W.The COF and wear rate of the different WC-12Co wear-resistant coatings was contrary to that of microhardness with the increase of laser power.At the laser power of 1500 W,low COF of 0.55 and wear rate of 2.15(± 0.31)×10-7mm3·N-1·m-1 were achieved.Similarly,when three layers of WC-25Co composite powders were cladded on the surface of 304 stainless steel,the W and C on the edge of WC-25Co composite powders melt partially in liquid Co as well as 304 stainless steel matrix,and then new carbides consist of lamellar WC,herringbone Co3W3C and dendritic Fe3W3C were formed.The WC-25Co wear-resistant coating with no porosity,cracks and drawbacks like decarburization were obtained,showing high densification and good metallurgical bonding with the substrate at the laser power of 1500 W.It is worth noting that with the increase of laser power,the microhardness of the coatings increased first and then decreased,the highest microhardness of 1400 HV0.3 was obtained at laser power of 1500 W.The COF and wear rate of the different WC-12Co wear-resistant coatings was contrary to that of microhardness with the increase of laser power.At the laser power of 1500 W,low COF of 0.60 and wear rate of 8.347(10.312)×10-7 mm3.N-1·m-1 were achieved.When one layers of WC-12Co composite powders were cladded on the surface of high-chromium cast iron,the W and C on the edge of WC-12Co composite powders melt partially in liquid Co as well as high chromium cast iron matrix,and then new carbides consist of lamellar WC and fish-shaped M3W3C(M=Fe,Co)were formed.At the laser power of 1500 W,a combination of high scan speed and high laser energy density made the largest melting amount of WC-12Co composite powders,thus induced the largest number of newly precipitated WC and M3W3C(M=Co,Fe)eutectic carbides were obtained.Moreover,except for a few micropores on the top of the coating,a dense section was obtained,showing a homogenous layerwise microstructure,which achieved a good metallurgical bonding between adjacent layers and scanning tracks.And a resultant high microhardness of 1429 HV0.3 was obtained,which was about 2.6 times larger than that of high-chromium cast iron.The wear loss of the coating is 0.4681 g,which was about 6.8 times larger than that of high-chromium cast iron.