Formation of titanium and aluminum films by supersonic free-jet PVD method

This paper presents the development of supersonic free jet PVD as a new coa ting method for structural material to overcome technical problems containe d in other coating methods. This PVD method consists of evaporation in gas atmosphere and deposition in vacuum, i.e., ultra-fine particles are formed, carried and deposited to form film in a space of connected chambers, where ultra-fine particles formed by the evaporation of material in an evaporati on chamber with helium gas atmosphere are carried to a substrate with gas f low generated by the pressure difference between the evaporation chamber an d a vacuumed deposition chamber and deposited with high velocity to form fi lm. This study aims to form the metallic films of titanium and aluminum with th e method and to elucidate the effects of control parameters for the develop ment of the method. The velocity of ultra-fine particles should be an impor tant parameter for the film formation. In order to increase carrier gas vel ocity to increase particle velocity, we designed a nozzle on the assumption of one-dimensional isentropic flow to attain the gas velocity of Mach 3.6 at the outlet of the nozzle. The results obtained are as follows: (1) Reduction of coarse particles by s uppressing the stagnancy and secondary agglomeration of particles is necess ary for producing metallic films of titanium and aluminum. (2) Growth rate of film increases in proportion to electric power to evaporate source metal . (3) To heat a nozzle is effective for the formation of film without voids . (4) No cracks were formed by indenting the diamond indenter of micro Vick ers hardness tester at the interface between substrate and coated film with the force of 4.9 N, which indicates strong adhesion between them.