Preparation And Performance Analysis Of ZrO₂/316L Stainless Steel Functionally Gradient Material

In this study,316 L stainless steel powder and 3%mol oxide yttrium partially stabilized zirconia powder were used as materials.First,the finite element analysis method was used to design the ZrO₂/316 L stainless steel functionally gradient materials.Temperature field and stress field of 316 L,composite material of 2 layer,graded material of 2 layers,graded material of 3 layers and graded material of 4 layers in actual working environment were analyzed with finite element analysis.Then ZrO₂/316 L stainless steel functional gradient material of two layers was successfully prepared by powder injection molding method.The components of these two layers were90%316L/10%ZrO₂ and 80%316L/20%ZrO₂ respectively.The optimum process parameters of feeding,injection molding,debinding and sintering in the process of preparation of FGM have been determined.The microstructure and structure of functionally gradient materials were observed and analyzed.The element distribution of interfacial transition zone and the hardness of the cross section were detected and analyzed.The research results showed that temperature field of FGM was a gradual transition inside the material.The more the gradient layers were,the better the temperature moderation was and the temperature gradients between different layers of materials were smaller.The thermal stress decreased with the increase of the gradient layers.The tensile strength of the material increased with the increase of the FGM gradient layers.Tensile stress and thermal stress of materials mainly concentrated in the interface between the layers,more interlayers could make greater stress relaxation effect and maximum stress and stress area were smaller.The tensile strength and thermal stress relaxation ability of ZrO₂/316 L stainless steel functionally gradient materials were better than those of ZrO₂/316 L stainless steel laminated composite and pure 316 L stainless steel.Reasonable preparation processes of ZrO₂/316 L stainless steel FGM were determined.Through a lot of experiments,the best preparation process was as follows:the powder loading was 56%?volume fraction?;Injection temperature,pressure,and holding time were 150?,80 MPa and 3s;Solvent degreasing was carried out in a water bath.The degreasing solvents was n-heptane.The degreasing temperature was 45? and the time was 4h.Then the removal rate of paraffin could be up to 90%.This provided the porous condition for thermal degreasing;The thermal debinding and sintering process were in resistance furnace.From room temperature to 420?,the average heating rate was about 2?/min.From 420? to 650?,the average heating rate was about3?/min.The heat preservations were performed at 250?,420?,550? and 650?,and the times of heat preservation were respectively 30 min,60min,60 min,60min;The optimal sintering temperature of FGM was 1320?.From room temperature to 900?,the heating rate was about 5?/min.Holding one hour at 900? in order to presinter.From 900? to 1100?,the heating rate was about 2.5?/min.From 1100? to 1320?,the heating rate was about 2?/min.The heat preservation was performed at 1320? and the holding time was 1h.There was no stratification or crack in the interlayer transition zone.The elements and the hardness changed continuously.The hardness increased with the increase of ZrO₂.