Research On Coprecipitation Preparation Technology And Sintering Microstructure And Propertise Of Cu-Co Pre-alloy Powders

Metal powder is widely used in powder metallurgy, lubricants, catalysts, conductive plastic, conductive fillers, electromagnetic shielding paint and other fields. More and more different types of metal powder is applied to the pre-alloy powder with the development of diamond tools. Low cobalt and ultra-fine is the development direction of the pre-alloy powder. Copper and cobalt have been widely used in traditional diamond tool matrix, but rarely reported in the pre alloy powders. The Cu-Co binary alloy powders coprecipitation preparation process and the effect of cobalt content and sintering temperature on sintered alloy organization and mechanical properties have been researched in this paper. The results of the study are as follows:1. Copper chloride and cobalt chloride have been used for the preparation of Cu-Co alloy powder by coprecipitation method. Oxalic acid has been used as precipitant. DSC-TG and XRD analysis results of precursor shows that the precursor is a kind of complex compounds. Scanning electron microscopy observation shows that the precursor is irregular small particles with a particle size of less than 1 m. The processing parameters of coprecipitation preparing conditions are 4.5-5.5 of pH, 50? of the reaction temperature,0.8 mol/L of the reactant concentration. The yield of the precursor has reached 95.76% and the particle size distribution of the powder is uniform under the condition of the process parameters. The median diameter powder is 12.94?m.2. Copper and cobalt alloy powder particle size increases with the increase of sintering temperature. The smallest diameter of the powder has been prepared from the sintering temperature of 350 C. With the reduction temperature rise from 350"C to 500?, the oxygen content of powder reduced first and then tend to be stable, and the particle size shows a trend of increase. When the reduction temperature is 450?, the oxygen content of powder tends to be stable, maintained at about 0.85%. The size of the powder particles is small.3. Copper and cobalt pre alloyed powder has become 2?m irregular particles with uniform particle size after reduction. Copper and cobalt alloy powder particles are scattered, and there are many holes between particles. Powder of actual elements (Cu:Co= 78.49:78.49) agree well with design elements (Cu:Co=4:1).Powder with antioxidant treatment is placed in air for 1 days and the oxygen content is 0.66%,which is 25% less than that of the powder without antioxidant treatment.4. Phase analysis of sintered alloy with different Co content shows only the Cu phase, which means Co elements have been fully dissolved into the Cu. The result of sintered alloy with cobalt content of 30% surface scanning shows uniform distribution of cobalt and copper in the sample. No element segregation phenomenon appears. The relative density of the alloy decreases with the increase of Co content. The bending strength and Vickers hardness of the alloy increases first and then decreases with the increase of Co content. The bending strength reaches the maximum value of 392.54MPa and the Vickers hardness reached the maximum value of 141.6 HV when the cobalt content is 30%.5. The microstructure of sintered alloy specimen with 30% Co becomes denser with the increase of sintering temperature.850? satisfies the copper and cobalt alloy powders sintering temperature. The relative density of the alloy reaches 96.37%,and the alloy have the best mechanical properties. The bending strength reaches 760.87MPa,and Vickers hardness reaches 167.5 HV. Sintering alloy grain grow and mechanical properties decrease when the sintering temperature rises to 900?.