Well I never! - I like the effect too.  I've got some old provia that I'll keep now!   I wonder what effect I'll get with diafine?  Massive grain perhaps.

Wait a minute - this is Kodachrome 64 processed in B&W chemistry?  It works?  No bleaching step or anything like that?  Just develop/stop/fix/wash?

If I am reading this correct, then your results are outstanding IMO.

I forgot to precise that the result of this process is a NEGATIVE B&W FILM : I started with a slide colour film and ended with a neg B&W film .

Very interesting , I also tried , years  ago , to develop C41 in B&W chemistry and as the respondent wrote , the orange mask is so dense that you need very long times in the enlarger and most of the images are low contrast But for some contrasty shots , it works very well with a very fine grain , almost not visible ,as you can't get with Tmax 100 .
As an other respondent wrote , with a reversal film , you get a nice neg with a light yellow hue which is no problem in the enlarger .
Thank you Carpents...

A brave experiment that worked! Nice looking images.

I have processed colour slide film in the past, and, with the film and chemistry I was using, you had to expose it to a specified light source for a given time mid way through the process. I presume that was the reversal part, that you have not done. Your results are rather more successful than mine, I seem to recall genuine colour, but with an unpleasant yellow cast.

...and you got a fine grain  . Did you try to enlarge the negs with an enlarger or did you scan them ?