Research On Metal Injection Molding Process Of Ti/TiH₂ Powder With POM-based Feedstock

Titanium has the advantages of high specific strength,good corrosion resistance and excellent biocompatibility.It has broad application prospects in the fields of aerospace,military industry,medical equipment and 3C products.However,the application of titanium alloys face two major problems:（1）The processing of titanium products is difficult.（2）The cost of titanium is high.Metal injection molding has the characteristics of high material utilization,large design freedom,and high dimensional accuracy,which can effectively solve the problem of titanium processing.Using cheap TiH₂ powder to partially replace spherical titanium powder can reduce the cost.In this paper,a high-efficiency POM-based titanium feed was prepared and applied to titanium powder injection molding,and the process of each stage of injection molding is studied.At the same time,different proportions of Ti/TiH₂ powder were used for metal injection molding,and the best powder proportion was obtained.Using spherical titanium powder and polyformaldehyde binder as raw materials,the optimal process of internal mixing,injection molding,debinding and sintering in injection molding of pure titanium powder was investigated.The following conclusions are as follows:（1）The pure titanium feed is pseudoplastic fluid in the molten state.（2）In the injection molding process,as the injection temperature,injection pressure,and injection speed increase,the bending strength of the injection blank first rises and then decreases.（3）In the catalytic debinding process,the optimal debinding time is 5 h,the temperature is 120℃.（4）In the sintering process,with the increase of the sintering temperature,the volume shrinkage and density of the sintered sample increase.The comprehensive mechanical properties first increase and then decrease slightly,and the optimum temperature is 1250℃.With the extension of the holding time,the volume shrinkage and density of the sintered samples increased.The mechanical properties first increased and then decreased,and the optimal performance was at2 h.（5）The samples sintered at 1250℃and 2 h were subjected to hot isostatic pressing at1000℃.The comprehensive mechanical properties have been improved.Using Ti/TiH₂ powder and POM-based binder as raw materials,the effects of different proportion of Ti/TiH₂ on injection molding feedstock,injection blank performance,catalytic debinding performance and sintered sample performance were studied.The following conclusions are drawn:（1）As the proportion of TiH₂ increases,the feed viscosity increases,the MFI index decreases,the non-Newtonian index n decreases,and the viscous flow activation energy E decreases.（2）As the proportion of TiH₂ increases,the bending strength of the injection blank gradually increases.（3）As the proportion of TiH₂ increases,the catalytic debinding rate decreases,reaching the expected debinding target.（4）As the proportion of TiH₂ increases,the volume shrinkage and density of the sintered sample increase,and the comprehensive mechanical properties decrease.The tensile strength of the sintered sample reduce the cost while maintaining good comprehensive mechanical properties,which is of great significance to the wide application of titanium alloys.