class 12 metric washers
 

class 12 metric washers?
hello
my understanding is that to prevent creep, even at moderate temperature, it is desirable to use a class of washer that matches that of the bolt. in the past, we have used class 12 washers when needed, to match class 12.9 fasteners.
recently, it has become difficult to obtain 12.9 fasteners, and all but impossible to obtain matched washers.
is there a reason for this?
does anyone know of a source for these parts? our only option seems to be having a very small run of custom hardened parts made, and this is going to be costly.
our previous suppliers now carry 10.9 only.
thanks in advance for any help