Study On Vitrified Bond CBN Grinding Tools For Titanium Alloys

Titanium alloy is becoming attractive material in many engineering fields, suchas aerospace, nuclear, warship, weapons, medical etc. in recent years. However, it iswell known as a difficult-to-machine material, and there are so many problems duringmachining process, such as: high grinding force, high grinding temperature, poorsurface quality and grinding wheel dull rapidly. Poor machinability and lowproductivity have been main reasons that can’t be applied widely. The main reason isthat titanium alloys have low thermal conductivity compared with other metals, thusthere will be a large number of heat focus on the grinding zone during grindingprocess. Vitrified CBN grinding wheels are the most ideal candidate during grindingtitanium alloys on account of their outstanding properties except for their strongbrittleness and low thermal conductivity. Vitrified bond and CBN grinding tools forgrinding titanium alloys were systematically investigated in this study. The basicvitrified bond with excellent properties was obtained by investigating the effects ofcomposition and sintering process on the vitrified bond and CBN grinding tools. Thenthe influences of different kinds of additives and amount on the vitrified bond andCBN grinding tools were also studied. The results were as follows.The mass ratio of Li2O/Na2O and ZnO content had a great effect on the vitrifiedbond and CBN grinding tools. The vitrified bond and CBN grinding tools hadexcellent properties when the mass ratio of Li2O/Na2O was0.3and ZnO content was2wt.%. The properties of vitrified bond were as follows, refractoriness:666℃,fluidity:258.09%, thermal conductivity:0.74W/m K, and the bending strength ofCBN grinding tools was62.35MPa. The effects of additives kinds (AlN、Al、Cu、graphite) and content on the refractoriness, fluidity, thermal conductivity of vitrifiedbond and the bending strength, microstructure of grinding tools were different,respectively. The thermal conductivity of vitrified bond was1.9W/m K with8wt.%graphite, which was the largest value after doping these different additives and about95%higher than that of the basic vitrified bond. However, the other properties ofvitrified bond and grinding tools deteriorated seriously. When added6wt.%Cu, thebending strength of the composites reached the maximum,71.88MPa, the thermalconductivity was approximately higher55%than basic vitrified bond, but the changesof the refractoriness and fluidity of vitrified bond were little. Al had an great effect onthe refractoriness and fluidity of vitrified bond, and it made the refractoriness increased obviously. After doping with6wt.%AlN, the refractoriness of vitrifiedbond was678℃, the thermal conductivity was1.44W/m K, which was about100%than that of the basic vitrified bond. Also the bending strength of the compositesreached66.35MPa, so the comprehensive properties were excellent.