Preparation And Erosion Performance Of Si₃N₄/1Cr18Ni9Ti Co-continuous Composites

Erosion wear is a kind of wear phenomenon that the surface of target materials damaged under the impact of flow of particles which are small and dispersed.Slurry erosion which is defined as liquid solid two-phase flow erosion wear is a common phenomenon in flow area of water conservancy machinery,mud pump,impurity pump,desulfurization pipeline and so on that liquid or solid particle impacts the surface of target material at a certain impingement angle and flow velocity and causes the surface loss of target material,which not only shortens the service life of the corresponding parts but also causes immeasurable economic loss.There is an effective method to improve the slurry erosion resistance of target materials,that is to develop new kind of co-continuous phase materials in which mutual confining action is very strong between two phases in the two-phase structure.In the present paper,Si3N4/1Cr18Ni9Ti co-continuous phase composite is successfully prepared with the matrix of lCrl8Ni9Ti austenitic stainless steel and the reinforcement of Si3N4 foam ceramic through the method of pressure casting.The bonding between the metal matrix and the foam ceramic reinforcement is good.The Si3N4 foam ceramic is prepared by gel casting.Relationships between erosion rate and impingement angle,flow velocity,sand content and erosion time of 1Cr18Ni9Ti stainless steel and Si3N4/lCr18Ni9Ti co-continuous composite are studied using a rotary disc-cycle slurry erosion device and erosion mechanism of both were discussed.Erosion rate of 1Cr18Ni9Ti stainless steel goes up first and then goes down as impingement angle goes up from 0° to 60°,the maximum erosion rate was 3 g·m-2·h-at 15°.Micro hardness of 1Cr18Ni9Ti goes up as impingement angle goes up from 0° to 60°.Material is worn away by ploughing at 0°,cutting and a little ploughing at 15°,transforming form cutting to pitting at 30°,pitting at 45°,pitting and a lot of sand embedded in the surface at 60°.Relationships between erosion rate of 1Cr18Ni9Ti and flow velocity are linear.As flow velocity goes up,micro hardness has a slightly increase but the way of erosion doesn't change.Erosion rate of 1Cr18Ni9Ti stainless steel has a linear relationships with sand content and erosion time.Increasing of sand content and erosion time neither changes the way of erosion nor micro hardness of the surface.Compared to 1Cr18Ni9Ti stainless steel,erosion resistance ofSi3N4/1Cr18Ni9Ti co-continuous phase composite is more superior.Erosion rate of composites has a lower level of fluctuation as a function of impingement angle than 1Cr18Ni9Ti stainless steel,the maximum value reaches 1.8 g·m-2·h-1 at 30°;erosion rate of composites has an exponent relationship with flow velocity(E?V0.67)and a linear relationship with sand content.Erosion rate of composites decreases with the elongation of erosion time and then stabilizes at 0.5 g·m-2·h-1 after erosion for 40 h.The main reason for the improvement of erosion performance is that the shadow protective effective of foam ceramic reinforcement to stainless steel matrix,besides,the foam ceramic reinforcement never exfoliates from matrix because of the strong restraining effect of the three-dimensional continuous network skeleton.