Plasma Nitriding Of Tantalum Microporous Ultra-Thin Materials

The spinneret is a key component of chemical fiber wet spinning.Its performance directly affects many economic indicators such as spinning quality,labor productivity,and cost,and is one of the important signs of the competitiveness of the textile machine market.Manufacturing spinnerets with tantalum instead of gold and platinum can significantly reduce textile costs.However,the hardness of the tantalum spinneret is relatively low.The microhardness of pure tantalum is 100-120 HV,while that of platinum is 200-300 HV.This results in the problem that the surface of the ultra-thin porous material made of tantalum is easy to be worn and scrapped,which restricts the wide application of the ultra-thin porous material made of tantalum in the chemical fiber industry.In order to solve the problem of low hardness of tantalum microporous ultra-thin materials,the common methods are to form a layer of lithium tantalate film on its surface,or to deposit diamond-like carbon film.However,the hard film covering the soft substrate will inevitably bring about bonding problems,and the film thickness is not easy to control.Plasma nitridation is a surface treatment technology that forms a high-hardness wear-resistant layer on the metal surface without bonding problems.This article mainly compares and studies the nitriding of tantalum microporous materials under the traditional direct current plasma nitriding（DCPN）and active screen plasma nitriding（ASPN）processes.Observe the surface morphology and phase composition,measure the surface hardness,fracture toughness,and evaluate its corrosion resistance in 10%H₂SO₄ solution.The following conclusions are drawn:（1）DCPN and ASPN studies of tantalum microporous ultrathin materials in NH₃ and NH₃+Ar found:After DCPN in NH₃ and NH₃+Ar atmospheres,a nitriding layer mainly composed of Ta N is formed on the surface of tantalum.The ASPN in NH3nitriding only forms a nitriding layer containing Fe₃N,Ta₂N and Ta N_0.04phases at a higher temperature,but Fe₃N phase can also be found at the lower temperature of ASPN sample surface under NH₃+Ar atmosphere.The surface hardness of all nitriding samples is higher than that of matrix.The surface hardness of the sample after DCPN nitridation is the highest,reaching 1039.2 HV_{1.0 kg}.The hardening effect of DCPN is more obvious than that of ASPN,but the toughness decreases seriously.（2）DCPN has studied in different N₂+H₂ nitriding atmospheres（N₂:H₂ is 3:1,2:1,3:2,1:1,2:3,1:2,1:3）:After DCPN in all atmospheres,the nitriding layer is dominated by Ta₂N phase,and the surface hardness of all nitriding samples is higher than that of matrix.The surface hardness of the nitrided sample is the highest at N₂:H₂=3:1,reaching 519 HV_{1.0 kg}.The results show that the corrosion resistance of nitriding sample is not decreased after nitriding in 10%H₂SO₄ solution.