Effect of Mo on microstructure and properties of laser cladding WC/Ni35 layers
In response to the issue that cracks are prone to occur in WC/Ni35 cladding layers with high WC content,2,5 and 8 mass％Mo elements were added to the WC/Ni35 cladding layers,and the effect of Mo on microstructure and properties of the WC/Ni35 cladding layers was studied.The results show that with the increase of Mo element content,the microstructure of the WC/Ni35 cladding layers becomes denser and finer,with a decrease in columnar crystals and an increase in equiaxed crystals.In the cladding layers with 2 and 5 mass％Mo elements added,the number of new hard phases such as Ni17W3 and Cr4Ni15W increases,leading to an increase in the average hardness of the cladding layers.In the cladding layer with the addition of 8 mass％Mo element,more phases exist as ductile phases containing Mo,and its average hardness is the same as that of the cladding layer with the addition of 5 mass％Mo element.When the Mo element content increases to 5 mass％,new W compounds are generated in the cladding layer,reducing the segregation phenomenon of W element.At the same time,the repair effect of Cr element on the passivation film improves the corrosion resistance of the cladding layer.The addition of 8 mass％Mo element in the cladding layer results in a Cr poor zone due to the precipitation of Cr,thereby causing a decrease in the corrosion resistance of the cladding layer.There are no cracks in the cladding layer with 8 mass％Mo element added.Adding 8 mass％Mo element to the WC/Ni35 cladding layer with high WC content can obtain a crack-free and dense microstructure,with an increased hardness and a slightly reduced corrosion resistance.
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