Preparation Of Fir-derived Carbon-derived SiC Ceramics And Their Frictional Wear Properties

Biomass SiC ceramic materials not only have excellent properties such as wear resistance,high hardness,corrosion resistance and oxidation resistance,but also have a wide range of raw materials,low preparation cost and good biocompatibility.etc.Therefore,it is considered an environmentally friendly material,and has a broad prospect of being widely used in mechanical,chemical,catalytic and biomedical fields,and has received extensive research attention at home and abroad in recent years.It has been widely studied at home and abroad in recent years.In this paper,we used cedar wood as raw material and obtained cedar wood biomass carbon source by high temperature secondary carbonization,and optimized the preparation process of biomass-based SiC ceramics by response surface experiments,and studied the effects of parameters such as carbon to silicon ratio,reaction temperature and adhesive dosage on the friction properties of prepared biomass-based SiC ceramics.The changes of microstructure,elemental composition and crystalline structure of the cedar-based SiC ceramic materials were characterized by means of XRD,SEM,EDS and other analytical tests.In terms of performance,the frictional wear behavior was studied by wear experiments,and the relationship between friction coefficient,friction force and wear amount was investigated,followed by the investigation of the frictional wear process and behavior mechanism by characterizing the frictional wear surface,as follows The main research findings are as follows:(1)According to the analysis of tissue phase and morphological structure,both Si and C in situ reactions occur at three different sintering reaction temperatures.Before 1400℃,the Si(s)+C(solid+solid)reaction is dominated,and SiC is generated by diffusion reaction,and the generated SiC is mainly granular,showing an angular morphology,indicating that SiC crystal growth has a selective orientation;above 1400℃,the reaction is dominated by Si(l)+C(liquid-solid),and the reaction rate depends on the spreading rate of liquid Si on the toner surface,and the C atoms are dissolved in liquid Si to form a supersaturated solution,and then SiC precipitates in the solution,and the reaction rate after SiC generation depends on the spreading rate of Si atoms in the SiC layer.(2)The level of factors was determined by single-factor experiments,and the preparation process of biomass-based SiC ceramics was optimized by response surface optimization analysis.Based on the single-factor experiments,the level parameters of the factors were determined as 3:7,4:6 and 5:5 for the carbon to silicon ratio,1200℃,1400℃ and 1600℃ for the reaction temperature,and 3%,5%and 7%for the adhesive dosage,respectively.-Behnken Design principle,using Design-Expert 11.0 software for data analysis,after the variance analysis of the friction coefficient and wear rate comparison,it is concluded that the reaction temperature has the greatest effect on the friction coefficient and wear rate of SiC ceramics,combined with the XRD and SEM data analysis of the surface layer and internal layer of the material,indicating that increasing the reaction temperature can promote the densification of the blanks,and at the same time,accelerate the growth of grains and whiskers,enhance the intergranular bonding,and improve the mechanical properties of the material.(3)In terms of tribological properties,FSCC was subjected to tribological wear experiments at room temperature,and its friction coefficient and wear rate were 0.384,0.576,0.763 and 4.64×10-4 mm3/N·m,6.83×10-4 mm3/N·m and 7.96×10-4 mm3/N·m under the load pressure tests of 5N,10N and 15N,respectively.As the load pressure increases,microcracks are easily induced on its surface,which expand rapidly and lead to brittle spalling and formation of abrasive grains,and its main wear mechanism is mainly controlled by plowing wear and abrasive grain wear.However,the friction and wear reduction properties of FSCC are greatly improved at high temperatures,and an oxide film layer with lubricating or wear reduction effect is generated on the friction surface of FSCC,and its friction coefficient and wear rate are 0.372,0.431,0.455 and 4.12×10-4 mm3/N·m,5.66×10-4 mm3/N·m,7.38×10-4 mm3/N·m.Since the hardness of oxide film layer is lower than FSCC,it is easy to produce lattice distortion,and at high temperature,the friction surface has certain plastic deformation ability,which raises the threshold of crack instability expansion and plays a very important role in high temperature wear lubrication,making SiC and its multiphase ceramics appear high temperature self-lubricating phenomenon.The wear mechanism is mainly minor abrasive wear and oxidation wear.(4)The frictional wear mechanism of FSCC was investigated by a combination of experiments and simulations.The experiments were carried out on a HT-1000 friction and wear tester,and an orthogonal test design was used to investigate the effects of load and rotational speed on the friction coefficient and the maximum equivalent force of FSCC,respectively.The geometric model of Si3N4 on the grinding ball and FSCC workpiece was established by ABAQUS finite element software,and a secondary user subroutine UMESHMOTION was developed to achieve an initial stable contact between the indenter and the ceramic disk using static analysis and implicit kinetic analysis,and then a kinetic analysis was performed to consider the ceramic as an isotropic material for friction analysis.And when the normal load is large,the friction force increases rapidly to a certain value within a very short sliding distance and then tends to level off,and the friction force is less affected by the rotation speed.As the rotation speed increases,the wider the area of stress concentration generated by FSCC,the more likely FSCC is to produce deformation,and the deformation becomes more and more obvious.