Experimental studies on surface treatment of Titanium by new blasting techniques

In industrial technology surface treatment by micro-blasting and micro-peening are increasingly used as they reach a high degree of surface refinement and strengthening. These methods are of interest in dental technology, especially for the treatment of Titanium castings. The aim of the present investigation is the experimental evaluation of a micro-dry-blasting-method (Gruber and Stübinger, Linz/Austria), using an abrasive and a spherical blasting medium, separate and in combination. Cast samples (20x10x2 mm) of Titanium (grade 1) were used for the experiments. Their initial surface conditions were - casted and cleaned in an ultrasonic bath - wett grinded on SiC-paper, grit size 220, 600, 1200. The finished surfaces were characterised by light- and scanning electron microscopy (SEM) and analysed profile-graphically (RZD, Sm). Surface near parts of the finished samples were light microscopically investigated on metallographic transverse sections. From the results the following conclusions can be drawn: 1. The abrasive micro-blasting of Titanium castings removes surface near layers and shows an levelling effect. Microstructural defects are extensively diminished. 2. Abrasive micro-blasting of surface ground before (SiC220) shows the same result, but in lower degree. Abrasive micro-blasting of fine-ground samples is of no use. 3. The micro-peening technique in combination with the foregoing abrasive microblasting or grinding effects a further levelling and compaction of the surface. The average distances of the peaks are increased. The investigated methods enable a rationalisation of surface finishing and an improvement of surface quality of Titanium castings. Their combination with usual milling and polishing methods of dental laboratories was tested and can be recommended. Keywords: finishing of Titanium, shoot peening, abrasive micro-blasting, surface levelling and compaction, metallographic structure, roughness