Microstructure And Properties Of Tungsten Carbide Particle Reinforced Wear Resistant Coating By TIG Cladding

In this paper,the tungsten carbide wear-resistant cladding with crack resistance was deposited by TIG.The main research content was divided into three parts:cladding process,microstructure analysis of cladding layer and performance test of cladding layer.In this paper,body energy was used instead of line energy to judge the size of the heat input of the cladding layer.The reduction of body energy can reduce the dissolution of tungsten carbide particles and increase the volume fraction of undissolved tungsten carbide particles in the cladding layer.Preheating base material can reduce residual.Cladding with swing can reduce the uneven distribution of tungsten carbide particles and avoid stress concentration caused by uneven distribution.Meanwhile,it can reduce the contact angle and improve the forming.After optimizing the process,three cladding layers were produced.Among them,2#welding wire(Nb-WC cladding layer)has the best crack resistance,which can be welded to the double layer without cracking.1#welding wire(Ni-WC cladding layer)can be welded to a single layer without cracking.0#welding wire(WC cladding layer)has the worst crack resistance.The tungsten carbide particles in the cladding layer were dissolved to form an M₆C type eutectic carbide.The phase composition of the cladding layer was mainly composed of three parts:undissolved WC/W₂C,M₆C type eutectic carbide and iron-based phase.The microstructure of the single-layer cladding layer is elliptical or oblong crystal grains and fishbone-shaped M₆C eutectic carbides at the grain boundary.The crystal grains of the Nb-WC cladding layer are the smallest.The double-layer cladding layer undergoes microstructural changes such as aggregation and growth of M₆C-type carbides,precipitation of fine dispersed carbides and transformation of retained austenite.The hardness of the cladding layer was significantly improved.There are two main factors affecting the hardness of the cladding substrate.One is the number and size of M₆C-type eutectic carbide phases precipitated due to the dissolution of tungsten carbide particles.The other is the amount of fine dispersed carbides precipitated.The wear volumes of the three cladding layers of WC,Ni-WC and Nb-WC were 1/55,1/48,and1/53 of the base metal,respectively.The wear mechanism of the cladding layer was the shadow effect of the carbide particles on the substrate and the supporting effect of the matrix on the tungsten carbide particles.The key factor affecting the wear resistance of the cladding layer was the content of tungsten carbide particles in the cladding layer.The wear volume of the cladding layer decreases as the distribution density of tungsten carbide particles on the wear surface increases.Finally,the reasons for the improvement of the crack resistance of the cladding layer are summarized,except for the above process factors.The addition of Nb promotes the precipitation of carbides in the matrix,consuming the carbon in the matrix,thus improving the toughness of the dark matrix.At the same time,the Nb element refines the size of the grains and precipitates carbides,thereby improving the crack resistance.