Study On Surfacing Technology Of Ceramic Particle Reinforced High Chromium Cast Iron Composite

Ceramic particle reinforced steel matrix composites have been widely used in the field of wear resistance combined the strength and toughness of steel with the high hardness and wear resistance of ceramic particles.The development of particle reinforced high chromium cast iron composites(Abbr.PRHC)improves the wear resistance of wear-resistant parts to a great extent.Compared with high chromium cast iron and surfacing high chromium cast iron,the composite has higher specific strength,specific stiffness,better heat resistance,lower coefficient of thermal expansion and higher dimensional stability,while the plasticity,toughness and machinability of composite materials are much better than ceramic.At present,ZTA PRHC are widely applied in the grinding fields such as grinding roller and disc of coal mill and vertical grinding roller.However,after the wear failure or damage,it will be discarded directly,which will cause great economic loss and waste of resources.Therefore,it is of great significance to carry out the research on the surfacing technology of PRHC,optimizing the surfacing process,and recycling of such composite materials by the method of hardfacing.In this paper,the orthogonal experiment method was used to study the surfacing welding process of high chromium cast iron.The optimized welding process is applied to majorize the temperature between the welding layers and the welding heat source distance from the upper surface of base metal high chromium cast iron to PRHC area.Firstly,the optimal welding process of high chromium cast iron was explored through observation and analysis on the stress release crack and microstructure of the deposited metal by means of intersection method and linear intercept method.Then,the effect of interlayer temperature and heat source distance on the microstructure and interface of the composite material on the ZTA particle-reinforced high chromium cast iron-based composite material were investigated using methods such as the stereo microscope,optical microscope,scanning electron microscope,and energy dispersive spectrometer.The results show that changes in welding current,welding speed and interlayer temperature will all have a significant influence on the microstructure and stress release cracks of the deposited metal.A good match between the three parameters is required to obtain a deposited layer with satisfied microstructures and properties.Through orthogonal experiments,the basic welding process parameters are obtained as follows:welding current 310-330 A,welding speed 900mm/min,and interlayer temperature less than 100?.The deposited metal microstructure obtained under the above process conditions has the highest carbide volume fraction,the highest hardness,and the most uniform stress release crack distribution.When using different interlayer temperatures for surfacing welding of ZTA particle reinforced high chromium cast iron-based composites,as the interlayer temperature increases,the interface between ZTA particles and high chromium cast iron gradually deteriorates.The higher the interlayer temperature is,the more defects such as ZTA particle fracture,debonding,and fracture and spalling of high-chromium cast iron are generated at the interface.When the bonding strength of the interface between ZTA particles and the metal matrix is less,When the bonding strength of the interface is less,not only the crack propagation cannot be prevented,but also easy to initiate new cracks at the interface.Under the condition of a heat source distance of 10 mm and the interlayer temperature of 30?,surfacing welding was carried out,and there was no obvious effect of welding on the interface of the composite zone.Using the aforementioned optimized welding process and using different heat source distances for surfacing welding of ZTA PRHC,as the heat source distance decreases,the influence become heavier on the interface between ZTA particles and high chromium cast iron.When the heat source distance is 0mm,the weld bead cannot be formed,causing the ZTA particles to melt and peel off.The fracture and spalling of ZTA particles are mainly due to the volume shrinkage and expansion under the influence of the welding heat source,when the fracture toughness of the material itself is exceeded,the defects such as cracks and spalling pits occur.When the heat source distance is 4mm,the interface between the ZTA particles and the high chromium cast iron also falls off,and some ZTA particles show blocky exfoliation;when the heat source distance are 8mm and 10 mm,there are no obvious impact on the composite material area.ZTA particles are closely combined with high chromium cast iron matrix,which can effectively resist the crack propagation at the interface.Therefore,when the interlayer temperature is 30 °C and the heat source distance is 8 mm,it is suitable for composite surfacing welding.