| In order to improve the mechanical property and operational life of cutting pick, a Fe-based cladding layer reinforced by WC of low cost, high wear resistance, about 2mm thickness was fabricated on the cutting pick surface by high frequency induction cladding (HFIC), according to the failure form and shape of the cutting pick.To fix the optimal WC content by doing the powder optimization experiment, and the influence of heat treatment on microstructure and properties of cladding layer were studied. Microstructrue of the coating and border was examined by means of optical microscope (OM) and scanning electron microscope (SEM). Phase compositions were certified by X-ray diffraction (XRD) and SEM-EDS. The surface rockwell and microhardness of the coating were tested on the rockwell hardness tester and microhardness tester, respectively. Abrasive wear resistance test was performed to evaluate the wear-resistance property of the coating. The relationship of microstructure and properties, solidification process and abrasion mechanism of the HFIC coating were studied. The results showed that:(1) A Fe-based coating was successfully produced on column surface by HFIC with a Al2O3 cylindrical sleeve, the coating was fully dense and uniform, without crack, and had a excellent metallurgical bond with the substrate.(2) The coating had apparent characteristic of quick solidification. We found that there were different solidification feature in different area, the microstructure was planar crystal near the border, then was cellular crystal and equiaxed crystals in the middle of the coating. The Fe-based coating comprised of austeniteγ-Fe and eutectic carbide (Cr, Fe)7(C, B)3. However in the composite coating reinforced by WC, the main phases of the coating wereγ-Fe, (Cr, Fe)7C3, WC and W2C et al.(3) After quenched at 950℃and tempered at 250℃, the border turned closer and more uniform, the austenite transformed into martensite, also with the precipitation of secondary carbide, with the increase of WC content, the quantity of secondary carbide precipitation increased, too. Meanwhile, the herringbone carbide were changed into blocky, also the amount decreased. (4) The rockwell hardness of Fe-based coating was about four times of the substrate, when the WC content was 20%, the figure reached 63.6HRC, which was the maximum in all specimen. The specimen with 15% WC had the highest microhardness which reached HV0.3 1166.3; the rockwell hardness and microhardness of the coating decreased after heat-treatment, which is atributed to that the quantity and shape of the carbide reduced and changed.(5) The specimen with 15% WC performed best in the wear test, the wear resistance of this coating was 256% higher than that of the substrate, the wear resistance decreased after heat-treatment, which was similar to the behaviour of hardness. The main wear form of the composite coating was micro-cutting and furrow, and the furrow was very shallow, so the coating showed excellent wear resistance.(6) The composite coating on cutting pick surface was successfully produced by HFIC, using the coating material of 15% WC+Fe-based alloy powder, and an excellent metallurgical bond between the coating and substrate was attained, the coating was uniform and dense, the hardness was way better than the requirement, also with the excellent wear resistance, what's more, the coating had less spark when rubbing.In sum, HFIC with a Al2O3 cylindrical sleeve can be widely applied to design coatings in the protection and reconditioning of the column, cone and other solid of revolution machine components. And this surface coating technology has a promising future. |
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