Study On The Preparation And Properties Of CrMo Steel Bonded Titanium Carbide

Steel bonded carbide,which has high hardness,low proportion,good high-temperature stability,has been widely used in making the industry molds,measuring tools and wear-resistant parts.At present,compared with the similar foreign materials,the domestic steel bonded carbide has some problems such as lower porosity,lower strength and more uneven microstrusture.We prepared low alloy steel bonded carbide containing Cr by traditional powder metallurgy method.We gave preference to the raw materials of TiC powder,steel matrix and optimized the preparation processes to improve the properties of the steel bonded carbide.We optimized the ball mill process,sintering process and heat treatment process firstly based on the GT35 steel bonded carbide.The result showed that the samples has good comprehensive properties when milled for 44 hours,sintering at 1440 ? with heating rate of 1 ? · min-1 above 600 ? and the density and transverse rupture strength(TRS)are 6.40 g·cm-3 and 1602 MPa.The effects of carbon content and titanium carbide are studied.The best properties get when the carbon content is 7.50 wt%.The samples have good properties when prepared by titanium carbide with 19.15 wt%:hardness of 68 HRC hardness,TRS of 1726 MPa.The steel bonded carbide are prepared by using different iron sources(reduced iron powder,electrolytic iron powder,carbonyl iron powder)as raw materials.The sample has the lowest properties when prepared by using reduced iron powder and the electrolytic iron powder comes second.The sample has the best properties when prepared by using carbonyl iron powder:hardness and TRS are 70 HRC and 2120 MPa,respectively.Extra-low ferrochrome powder is used to prepared steel bonded carbide and compared with chromium powder and low,medium,high ferrochrome powders.The sample has good properties when prepared by using extra-low ferrochromium powder which has smaller particle size and higher purity.The hardness and TRS are 68 HRC,1893 MPa,respectively.Steel bonded carbide with different chromium content(2.34,6,10 wt%)which added different carbon contents are prepared.The TRS decrease and the hardness increase first and then decrease with the increase of chromium contentwhich are determined by the content of martensite and the shape,size,composition of the precipitated carbide.The sample with chromium content of 6 wt%has the best wear resistance,followed by the sample with chromium content of 10 wt%,and the sample with chromium content of 2.34 wt%has the worst wear resistance.The wear resistance of the samples(chromium content of 2.34 wt%)with atomized ferrochrome powder increase about 39.3%compared with the sample prepared with high carbon ferrochrome powder and is about 2.1 times higher than cemented carbide of YG25.We did the optimization experiment according to the above researches for the steel bonded carbide with chromium content of 2.34 wt%which is used more.The steel bonded carbide has good comprehensive properties(hardness of 70 HRC,TRS of 2286 MPa,impact toughness of about 7.2 J/cm~2)after heat treatment when prepared with carbonyl iron powder,19.15 wt%carbon content titanium carbide powder and extra-low ferrochro powder as raw material,total carbon content of 7.5 wt%,the milling time of 44 h,sintering temperature of 1440 Cheating rate of 1 ?·min-1.