微晶蜡基粘结剂应用于YG10硬质合金注射成形的研究

Development of the injection molding of YG10 cemented carbide with microcrystalline waxy binder

以微晶蜡等有机物作为粘结剂,进行WC-10Co(YG10)硬质合金的注射成形研究。原料粉末和粘结剂经混炼、破碎和过筛得到喂料,随后进行注射成形、脱脂和烧结。考察了注射温度、注射压力等工艺参数对成形性能的影响。实验结果表明:注射参数为注射温度为150℃、注射压力为11 Mpa和模温为40℃的条件下,可获得密度较高且无缺陷的注射成形坯体。成形坯体经溶剂脱脂和热脱脂后,最终在1400℃真空烧结90 min,可获得相对密度达99.5%、抗弯强度达2019 MPa、硬度为91.7HRA、钴磁为8.76 Gs·cm^(3)/g的YG10烧结体。

To overcome the shortcomings of conventional injection molding with paraffin based binder for cemented carbide,such as easy phase separation,unstable property of feedstock,slow debinding rate and poor shape conformation,a binder system with microcrystalline wax(MW)as the main component was employed to injection mold WC-10Co(YG10)cemented carbides.The optimized parameters of mixing,injection,debinding and sintering were investigated to obtain YG10 cemented carbides with excellent performance.WC and Co powders were mechanically premixed,then added into an internalmixer with microcrystalline wax(MW),high density polyethylene(HDPE),stearic acid(SA)and some other binder components according to the ratio.Banbury mixing was performed at 180℃for 2 h.After crushing and screening,the resultant feedstocks were added into the injection machine for injection molding to get green bodies.The binder in the green bodies were removed by a combination of solvent debinding and heat debinding.The debinded compacts were sintered in a vacuum furnace.Effects of injection temperature,pressure and other process parameters on the density and surface defects of the injected green bodies were investigated,and the debinding behavior of injected green bodies under different debinding solvents and different debinding temperatures was studied.Thermogravimetrics was performed on the injected green compacts,and suitable heating debinding process was developed.Furthermore,by changing the mass fraction of carbon black in sintering filler,sintered YG10 cemented carbides samples with excellent performance were obtained.The experimental results show that the density of injection body increases first and then decreases with the increase of injection temperature,and increases first and then stabilizes with the increase of injection pressure.The debinding speed of the sample in trichloroethylene solvent is higher than in kerosene sovent,and the suitable solvent debinding temperature is about 35℃,resulting in a higher solvent debinding rate and flawless samples.The binder in the green compacts can be completely removed by the thermal debinding process of slowly rising temperature and holding heat at 200,350,450 and 650℃respectively.The sintered body with excellent properties can be obtained by vacuum sintering at 1400℃.Under the conditions of injection temperature 150℃,injection pressure 11 MPa and mold temperature 40℃,the injection molding body with high density and defectless can be obtained.After solvent debinding and heat debinding,YG10 sintered bodies with relative density of 99.5%,bending strength of 2019MPa,hardness of 91.7HRA and cobalt magnetism of 8.76 Gs·cm~3/g can be obtained by vacuum sintering at 1400℃for 90 min.