the improved filler metal for use in the welding of ni — cr — w alloys that are excellent in high - temperature strength and corrosion resistance and which are used in the hot - zone structures of high - temperature gas - cooled reactors , gas turbines , etc comprises on a mass basis c ≦ 0 . 05 %, mn ≦ 0 . 1 %, si ≦ 0 . 1 % , cr = 17 - 20 %, w = 20 - 23 % , ti = 0 . 02 - 0 . 1 %, zr ≦ 0 . 03 %, y ≦ 0 . 015 %, b = 0 . 0003 - 0 . 01 %, al ≦ 0 . 1 %, mg ≦ 0 . 05 %, nb ≦ 0 . 06 % , the balance being ni and incidental impurities .