Study On Microstructure And Properties Of TiB₂-TiC-Co Cermet Coating Sprayed By Atmospheric Plasma

In the rapid development of science and technology today,failure form such as fatigue,corrosion and wear of metal mechanical components are huge obstacles that limit their widespread use.TiB₂-TiC ceramic composites have a wide range of applications in the field of metal protection due to their unique high melting point,high hardness,excellent wear and corrosion properties,and excellent chemical stability at high temperatures.In this paper,we prepared TiB₂-TiC-Co metal-ceramic powders by SHS technology and TiB₂-TiC-Co composite coatings on Q235 steel matrix by APS technology,studied the mechanical properties,and thermal shock resistance,wear resistance and corrosion resistance of the coatings,and the related mechanism is discussed.In this paper,TiB₂-TiC-Co spray powders are prepared by SHS with Co,Ti and B₄C as raw materials.The analysis of the product shows that in addition to the main phases of TiB₂,TiC and Co,there are a few diffraction peaks of intermediate phase Co₂B and residual metal Ti;With the increase of Co content in the coating,the number and size of ceramic grains decrease,and Co₂B content increase.The TiB₂-TiC-Co composite coating was successfully prepared by SHS technique,and the intermediate and residual Ti were transformed into the final ceramic phase.The main bonding mode of the metal-ceramic coating is mechanical bonding with good interfacial bonding;the bonding strength of the coating is higher than 10 MPa,and the TiB₂-TiC coating with 10 wt.%Co content has the highest bonding strength of23.75 MPa;the microhardness of the coating exceeds 700 HV,and the TiB₂-TiC coating with 5 wt.%Co content has the highest hardness of 1086.6 HV.The bond strength of TiB₂-TiC remains above 10 MPa after 20 thermal shock cycles at 400?and 500?,with good thermal shock resistance.The coating with10 wt.%Co has the lowest wear loss rate(1.1634*10^-7g N^-1m^-1)and coefficient of friction(0.5671),and at low Co contents.,the coating exhibits adhesion wear and delamination wear.The coating exhibits abrasive wear,hard phase stripping,abrasive wear and scratch under low stress at higher Co contents.Electrochemical performance tests showed that the coating had good resistance to electrochemical corrosion for Co content of 10-15%.