so for the hickosaurs it was right. The reason you have a problem is because it should be double quotes for wildcards, since with single quotes it takes them as alphabetic characters, and not for the value you want.
sed -i "s/abc=.*$/abc=def ghi/g" hpq_sf_attach_wf_param.txt
, "def" "ghi" , "\" .
sed -i "s/abc =. * $/abc = def\ghi/g" hpq_sf_attach_wf_param.txt