Protectively coated nickel or cobalt articles and process of making

Claim 1

AN ARTICLE COMPRISING (1) A BODY OF A METAL MATRIX SELECTED FROM THE GROUP CONSISTING OF (A) AT LEAST ONE METAL OF ATOMIC NUMBER FROM 27 TO 28, INCLUSIVE, AND (B) ALOYS IN WHICH THERE IS AT LEAST 50% BY WEIGHT OF AT LEAST ONE METAL OF ATOMIC NUMBER FROM 27 TO 28, INCLUSIVE, ALLOYED WITH AT LEAST ONE GROUP VI-B METAL OF ATOMIC NUMBER BELOW 75, SAID MATRIX METAL BEING DISPERSIONSTRENGTHENED WITH A PARTICULATE REFRACTORY METAL OXIDE HAVING A FREE ENERGY OF FORMATION AT 1000*C. GREATER THAN 100 KILOCALORIES PER GAM ATOM OF OXYGEN, (2) A TRIPLEX COATING ADHERENTLY BONDED TO AND INTEGRAL WITH SAID FIRST BODY, SAID COATING COMPRISING (A) AN INNER DIFFUSION ZNE COMPRISING AN ALLOY OF SAID MATRIX METAL WITH AN INCREASING CONCENTRATION OF CHROMIUM UP TO ABOUT 50% BY WEIGHT IN THE OUTWADLY DIRECTION, (B) A SECOND ZONE, OUTWARD OF ZONE (A), COMPRISING AN ALLOY OF SAID MATRIX WITH ABOUT 50 TO 95% BY WEIGHT OF CHROMIUM AND UP TO 10% BY WEIGHT OF ALUMINUM AND HAVING SAID PARTICULATE REFRACTORY OXIDE DISPERSED THEREIN, AND (C) AN OUTER ZONE COMPRISING AN ALLOY OF AT LEAST ONE MEETAL OF ATOMIC NUMBER FROM 27 TO 28, INCLUSIVE, CONTAINING, BY WEIGHT, ABOUT FROM 10 TO 50% OF ALUMINUM AND 2 TO 30% OF CHROMIUM.