Coated carbide cutting tool is the most important cutting tool in the world, because of the coating and the carbide matrix composition difference is too big, the waste coating carbide in the recycling process needs to be stripped of the coating. In this paper, different grades of carbide spray coatings were used as experimental materials, and the peeling of their surface coatings was studied by different methods. The surface morphology, chemical composition, structure and properties of the samples were analyzed by using 3D high field depth microscope, scanning electron microscope, EDS, EDX, XRD and microhardness tester. The results show that:

1) the TiN coating on the surface of waste cemented carbide can be completely removed by using the alkaline solution of potassium oxalate and hydrogen peroxide. The optimal ratio of the solution is K2C2O4(0.5mol/L), H2O2(3mol/L) and PH=13. There are three kinds of corrosion, including spot corrosion, crevice corrosion and uniform corrosion. Pitting corrosion and crevice corrosion are caused by pitting, crevice and other defects of TiN coating. During TiN coating stripping, uniform corrosion is the main method. After TiN coating stripping, nitrogen exists in the form of NH3 or ammonia, and titanium dissolves in the solution in the form of TiO(C2O4)22.

2) the TiN/ alpha-al2o3 /TiCN coating can be effectively removed by the mixed molten solution of sodium hydroxide and sodium carbonate. The best coating removal effect can be obtained by the molten salt method under the conditions of 700 degrees and 40 min, but the damage to the substrate is large, and the quality loss rate of the sample is up to 3.32%. Alpha -Al2O3 coating is removed mainly by reaction with sodium hydroxide solution.

3) the multi-component composite carbide spray coatings containing A1203 can be quickly and efficiently peeled off by physical pretreatment and independently developed coating stripping solution. In the process of dissolution method, the pretreatment method has a great influence on the rate, effect and morphology of the hard alloy matrix. In the process of high temperature treatment, the coatings of TiN and Ti(C, N) with low oxidation temperature crack and form a large number of grid-like micro-cracks. The loose oxidation layer rapidly reduces the hardness and reduces the bonding strength between the coating and the substrate. Sandblasting process destroys the coating structure, causing bulges, cracks and holes in the coating, reducing the adhesion between the coating and the substrate, and speeding up the peeling rate of the coating. The best pretreatment method of the dissolution method is the high temperature treatment of 450 degrees for 90 min, and the cooling method is air cooling. Under this pretreatment method, the coating can be completely removed after the sample reacts in the stripping solution for 24 h, and the mass loss rate is about 1%.

Related link:

http://www.wococarbide.com/Library/index.html

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