Research On High-Temperature Wear Resistance Of Laser Cladded Coating On Hot-Forging Die

Hot-forging die, due to the long stands with repeated high temperature, high mechanical, the mold cavity temperature reaches500℃, which easily produces high temperature oxidation, high temperature wear and other local position of failure. The high temperature wear is the main failure for hot-forging die, so how to improve the high-temperature wear resistance is the key to extend its service life.As a new surface modification technology, the coating can obtain even tiny structures and show a metallurgical bond with the substrate. Different alloys and ceramic powder are cladded on the surface of the hot-forging die, in order to improve the properties and life greatly.Co-based alloy has good wear and corrosion resistance, but has a low high temperature wear resistance. Adding ceramic powder in Co-based alloy can improve the high temperature wear resistance of the hot-forging die. Solid WC purchased is tiny but easily decomposed when laser irradiates, which limits weld depth with Co-based alloy and the layer cracks easily. Meso-porous WC has the similar size with Co-based alloy, and has many tiny pores. Co-based alloy after melting can fill the pores, enhance the toughness of meso-porous WC, and suppress the crack tendency. In this paper, Co-based, Co//solid WC and Co/meso-porous WC were to be selected as cladding materials.The Co-based and WC composite power were cladded by diode laser on the surface of H13substrate in this paper. The microstructure and phase of the laser cladded layer and phase composition were characterized by SEM, EDS and XRD. The microhardness of the coating was examined by microhardness tester and the wear property was examined by high temperature wear test machine.The results show that Co/solid WC, Co/meso-porous WC laser cladded layers have different microstructures and phase compositions. Co/meso-porous WC coating has better thermal stability than Co/solid WC coating. Co/solid WC coating had crack and uneven microstructure, the fine dendrites form in the middle and upper of the layer, and the small WC particles exit in the bottom. The coating consists of7-Co, hard phase CoCx, WC,(C6. At600℃, the high-temperature wear resistance of the coating increases two times related to that of the substrate. The wear mechanism of cladding coating is dominated by abrasive wear and adhesive.Co/meso-porous WC coating has no crack and is composed of hard carbide phase composition from top to bottom. The hardness of the layer is relatively uniform. The coating is mainly composed of y-Co and carbide hard phases WC, W2C,(Cr, Co)23C6and Cr7C3. Due to the dispersion strengthening and solid solution strengthening effects from meso-porous WC particles on the cladding layer, the wear resistance of the cladded layer at600℃increases by3times related to that of the H13substrate. Oxidative wear is the predominant high temperature wearing mechanism of the coating.