Research On Powder Injection Molding Of Ti(C, N) Based Cermets

As a new kind of materials which appeared in 1970s, the Ti(C, N) based cermets have good properties. Powder injection molding which appeared in 1920s as a new near-net-shape technology of combining plastic injection molding and powder metallurgy will spread applications of cermets, if it is applied to made complex shape productions. Based on the ideas, PIM technology of Ti(C, N) based cermets and some basal aspects relating are investigated in this paper. Ascertaining the suitable surfactant and its content, the he dispersing agent which contained 1.5wt% PVA and 1.0wt % CTAB could effect constrain the agglomeration of mixed powders. The mechanism of the dispersion of mixed powders was investigated by FTIR and zeta potential. A suitable wax-based binder is developed, which meet the requirement of PIM of Ti(C, N) based cermets. It consists of Paraffin Wax (PW) of 70 percent, High-Density Polyethylene (HDPE) of 15 percent, Ethylene Vinyl Acetate (EVA) of 10 percent and Stearic Acid (SA) of 5 percent. The thermodynamics parameters and solubility parameters of binder ingredients were calculated, and these binder ingredients are compatible. The mixing process of binder and powders was investigated with the method of mathematical statistics. The uniformity parameters (Hs) and the relation of uniformity parameters (H) and mixed times (n) are established. H_s = 100% ?Cv H = 97.73 +exp(0.096n+0.542) Influence of key injection molding process parameters on the quality of the injection molded specimens is studied and the parameters are optimized using orthogonal arrays experimental design and statistical analysis method. The result shows that not only the levels of parameters but also some interaction between parameters has great influence on the quality of the green parts. The optimized injection parameters are as following: injection pressure 8MPa, injection temperature 135℃, injection speed 40mm/s and holding pressure 8MPa. Three steps of the thermal debinding of binder for PIM was established by the studying of weigh loss-temperature curve. A mass of PW and a little of EVA was expelled between 170℃and 345℃. EVA was expelled at the range between 345℃and 440℃. The debinding speed could improve because the continuum pores was formed. Residual binder was debinding between 440 ℃and 500 ℃. Based in the TGA curves, the debinding program and method was established. The sintering process of Ti(C, N) based cermets of PIM was improved, according the traditional sintering process of Ti(C, N) based cermets.