Investigation About Laser Cladding WC/TiC/Co Coating On YG8 Cemented Carbide Surface

Cemented carbide is widely used in production and manufacture because of its great properties,like high hardness,high wear resistance,and so on.With the development of mechanical equipment and increase of procesing requiremnet,researchers begin to pay attention to its failure.There have been many ways to improve cemented carbide.This article aims to fabricate WC/TiC/Co coating on YG8 cemented carbide surface by laser cladding,then on this basis make further exploration.Cemented carbide is sensitive to temperature change and brittle,so it is necessary to find a suitable method,comparing presetting powder pulse laser cladding and coaxial powder feeding continuous wave laser cladding,it could be find that using pulse laser cladding could make a smooth cladding layer,but it is easy to crack,steady continuous wave laser cladding is a better choice.Through more tests get suitable parameters to fabricate good coating,then scanning electron microscope(SEM),energy disperse spectroscopy(EDS)and X-ray diffraction(XRD)were used to understand microstructure and analyze phase compositions,in addition,using microhardness tester to test hardness distribution of sample,wear resistance could be acquire through a series of friction-wear tests.The results show that coating surface is flat and bonded to the matrix tightly,cross section morphology is fine without obvious defects.WC particles could be find in surface layer and edges while disappear in cladding layer,and new homogeneous microstructure is observed in cladding layer.In heat affected zone,WC grains take place recrystallization and gather because of heat effect of laser.The phases in cladding layer are mainly composed of WC?W₂C?(Ti,W)C_1-X?M₆C(Co₄W₂C?Co₃W₃C),etc,those hard phases and carbides appeare and disperse,which resulte in dispersion strengthening,greatly enhance performance.After detection,the microhardness of the cladding layer can reach1783HV,which is obviously higher than the common YG8 cemented carbide(1598HV),while the microhardness of heat affected zone and matrix have slight reduction.Wear resistance of processed surface is heightened effectively,compared with YG8 cemented carbide,wear volume of cladding layer reduced by 90.67%,and average friction factor is 0.293,abrasive wear is major wear forms,surface layer is also hard-wearing because of tight connection between WC particles and Co,while wear forms are abrasive wear and delamination wear.On this basis,trying to begin multi-track overlapping laser cladding,it is find that heat accumulation is obvious in the test,when overlap rate is 30%,matrix temperature has a perceptible rise in this process,a lot of WC particles pile up leads to thick surface layer and bad morphology,there are many pores and fall of particles in cross section.when overlap rate is 20%,surface is uneven and has a thicken trend,according to these results and analyzes,adjusting overlap rate is 25%,and giving cooling time after every end of scan can obtain a relatively flat coatings,but there are big pores appear between adjacent two cladding layer.On the other hand,irregular WC particle is also used to test,compared with using spheroidal WC particle,irregular WC particle is hard to stack,new cladding layer is flat,thin,and not so coarse.