Research On Microstructure And Properties Of WC-Co Cemented Carbide Prepared By Selective Laser Melting

Cemented carbide materials play an important role in the manufacturing industry.It has good wear resistance and corrosion resistance,as well as high hardness,strength,rigidity and other excellent mechanical properties,which are widely used in cutting tools and drilling equipment,molds,measuring tools and other occasions.In this paper,the WC-12Co cemented carbide was fabricated via selective laser melting（SLM）technology.The effect of different substrates,and process parameters on density,microstructure,mechanical properties,friction resistance,and corrosion resistance were explored.The main conclusions are as follows:（1）WC-12Co cemented carbide samples was fabricated by SLM on 304L stainless steel substrate,the phase analysis showed that increase t of the?phase with the improvement of laser energy density.The?phase structure on the WC-20Co substrate was significantly more than the samples on the 304L stainless steel substrate.The WC phase were decomposed dramatically on account of the higher thermal conductivity of the WC-20Co substrate.（2）The effect of forming processes on the microstructure of cemented carbide with different substrates was studied.The coarse and fine WC grain regions with light and dark alternating distributions appeared on the transverse and longitudinal sections,but the distribution of molten pools and the layer structure on the longitudinal section was not obviously.With the increase of laser energy density,the sample exhibited the increase of the thermal cracks and the obvious overburning,but the microstructure was well-distributed and more density.better forming of the cemented carbide with the 304L stainless steel substrate,while it had more uniform and dense using the WC-20Co cemented carbide substrate.（3）with the increase of laser energy density,the cemented carbide on the 304L stainless steel substrate and WC-20Co substrate exhitbited the increase of residual streases,the increase of?phase,and the increase of Rockwell hardness.In the transverse test,the change of fracture strength from cemented carbide on different substrates were similar.With the increase of laser energy density,the bending strength of cemented carbide increased and then decreased.With the increase of laser energy density,the density of cemented carbide increased,and the pores decreased,causing the increases of strength.However,high laser energy density could cause excessive residual stress and thermal crack in the structure.Meanwhile,the over-burning phenomenon could be serious due to the increase of laser ener gy density,which lead to the decrease of fracture strength.Tthe WC phase was a typical transgranular fracture,and the fracture structure exhibited obvious dissociation steps.The Co binder presented a uniform network distribution.（4）After forming a cemented carbide sample on a 304L stainless steel substrate,the friction and wear resistance properties under high temperature conditions were tested.The wear resistance of cemented carbide at room temperature was excellent,but as the temperature increases,the friction factor and the wear of loss increased.At 600°C,the WC in cemented carbide decomposed and oxidized,the friction factor of cemented carbide decreased,and the wear of loss increased.This is because under the plastic wear mechanism,damage occurs between the friction pairs,the friction head falls off,and the matrix exhibits uniform sliding friction.（5）With the concentration of the H₂SO₄ solution increased,the corrosion resistance of cemented carbide was better,and the corrosion rate was slower.In the Na OH solution,the corrosion of the WC phase was aggravated.As the concentration of the Na OH solution increased,the corrosion resistance of cemented carbide became worse,but the corrosion resistance increased and the corrosion rate slo wed down.SLM fabricated WC-12Co cemented carbide specimens have good resistance to strong acid and alkali corrosion.