Research On The Effect Of Titanium On The Microstructure And Properties Of High Chromium Cast Iron Alloy Laser Cladding Layer

In this study，laser cladding was carried out by using diode laser withco-axial synchronous powder feeding to obtain high chromium cast ironalloy coating on low carbon steel. Different amount of titanium was addedinto the cladding alloy in order to improve the comprehensive mechanicalperformance of the cladding layer.The correlation between laser cladding parameters and the propertiesof the cladding layer was investigated. Through orthogonal experimentaldesign，the optimized parameters were obtained, which were: laser powerP=1.4kw, laser scanning speed Vs=8mm/s, powder feeding speedVp=30g/min, the flow rate of carrier gas Vc=7L/min. Under optimizedparameters, cladding layer with good forming, low dilution, metallurgicalbonding with the substrate was obtained.The effect of titanium on the microstructure of high chromium castiron alloy cladding layer was studied. The results showed that themicrostructure of cladding layer without titanium was composed of primary （Fe, Cr）₇C₃carbides and eutectic structure which was Fe-Cr solidsolution phase and eutectic （Fe, Cr）₇C₃carbides. The primary carbidesgrow along the cooling direction with hexagonal rod shape. With theincrease of titanium, the microstructure transformed from hypereutectic tohypoeutectic, the （Fe, Cr）₇C₃carbides were refined gradually and theamount of Fe-Cr solid solution phase increased gradually. Added titaniumcan react with carbon to form TiC with block and dendritic shape, thereason why TiC was shaped like this was explained. The volume fractionof TiC also increased with the increase of titanium. Thermodynamiccalculation confirmed that TiC can form prior to other products within theFe-Cr-Ti-C system.The effect of titanium on the properties （hardness, fracture toughness,wear resistance, etc） of the cladding layer was studied. The Vickershardness of the high chromium cast iron alloy cladding layer ranged from913.1HV to979.8HV. The hardness increased firstly and then decreasedwith the increase of titanium. When4wt.%titanium was added, thehardness of the cladding layer was highest. The fracture toughness of thecladding layer was measured through indentation method. The fracturetoughness of cladding layer increased gradually with the increase oftitanium, which was contributed by the improvement of carbides shape and refinement of the eutectic structure. There were transverse cracks inhigh chromium cast iron alloy laser cladding layer, which wereductility-dip cracks. With the increase of titanium, the length of cracksdecreased gradually. However, cracks cannot be eliminated by addingtitanium. The main wear mechanism of the cladding layer was abrasionwear. With the increase of titanium, the wear resistance of the claddinglayer increased firstly and then decreased.