| The property of the tool materials is the most important factor to ensure the product's shape accuracy during the cutting.The temperature of the cutting tool can reach 600-800°C or even 800-1000°C under normal case,and the oxidation of the tool materials will happen.Therefore,This paper mainly studied the impact of AlN addition on the microstructure and high-temperature oxidation behavior of Ti?C,N?-based cermets materials.The experimental results show that Ni in the cermet matrix reacts with AlN to synthesize Ni3Al phase in situ during liquid-phase sintering.When the addition amount of AlN is 2.5%,the hardness of the cermet sample is improved due to the solid solution strengthening effect of Ni3Al;however,as the content of AlN is continuously increased?5%AlN and 7.5%AlN?,two types of cermets The grains also increase,resulting in a decrease in the hardness of the cermet specimens.At the same time,the transverse rupture strength of both cermet specimens also rapidly decreases.According to the oxidation experiments at different temperatures and the same time,it can be seen that when the oxidation temperature is 900°C,and the amount of AlN added is 2.5%,the weight gain of the sample is minimal,and a dense oxide film exists on the surface of the cermet sample?NiAl2O4?.The presence of an oxide film hinders the further diffusion of oxygen atoms into the matrix,thereby exhibiting good high temperature oxidation resistance.However,when the addition amount of AlN is more than 2.5%,due to the presence of a large number of pores inside the cermet sample,the matrix exhibits lower oxidation resistance.When the oxidation temperature is1100°C,the growth of the oxide layer of the cermet sample containing 0%AlN is extremely serious,and the diffraction peak of Ti?C,N?or Ti(O0.19C0.53N0.32)is also significant.Also disappeared,the degree of oxidation is very high.However,in the XRD pattern of 2.5%AlN cermet samples,diffraction peaks of Ti?C,N?or Ti(O0.19C0.53N0.32)still exist.When the addition amount of AlN is more than 2.5%,there are a lot of hole defects in the oxide layer of the sample,and the grain growth is extremely serious,showing a lower high-temperature oxidation resistance.According to the oxidation experiments at different times and temperatures,it can be seen that the increase in oxidation weight of the AlN cermet samples does not increase with the extension of the oxidation time and follows a linear law.With increasing time,the weight gain and oxidation rate of the 2.5%AlN sample were significantly reduced,and the oxidation kinetic curve was parabolic;in contrast,the 5%AlN sample added to the oxidation weight gain and oxidation of the rate slightly increased;however,when the amount of AlN added was 7.5%,the oxidation kinetic curve became a linear pattern.The XRD pattern analysis,SEM morphology characterization and EDX energy spectrum analysis of the samples with oxidation time of 2h and 4h respectively show that the grain growth of the cermet oxide layer without AlN is obvious,and Ti?C,N?of diffraction peaks indicates that the surface of the cermet sample has been completely oxidized;and the surface of the cermet sample added 2.5%is covered by an oxide layer?NiAl2O4?,which improves the high-temperature oxidation resistance of the cermet sample;When the addition amount of AlN is more than 2.5%,a large number of micropores are generated inside the matrix,so the sample exhibits lower high-temperature oxidation resistance. |
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