in the embodiment depicted in fig2 and the cap 74 hub 70 and forward retainer 82 depicted in fig3 are fabricated from titanium or titanium alloy and preferably have a coefficient of expansion alpha of six 6 microinches per inch per degree fahrenheit and are installed in the outer ring 100 which is made from say molybdenum or other element that exhibits an alpha of three 3 obviously the molybdenum with the lower alpha would expand less than the titanium cap when both are heated to a high temperature and hence cause compression allowing diffusion bonding to occur at the interfaces between the vane ends and the respective caps an additional intermediate ring 106 and inner ring 104 may as an option be applied to the areas depicted in fig4 and these rings are made from a higher alpha than the titanium and serve to further increase the compression a suitable material for rings 106 and 104 may be a nickel alloy with an alpha of nine 9 or other well known or suitable material the tooling rings i e rings 100 106 and 104 are sized to provide the compression required to allow diffusion bonding to take place fig5 and 6 exemplifies another embodiment of this invention that fabricates the cap into annular segments and avoids the requirement of the forward retainer as noted in fig5 and 6 the hub.