ARMY TM 5-6115-612-34 NAVY AG-320B0-MME-000 (4) Spray coating (a) Place   part   in   fixture   designed   to   permit uniform coverage of areas designated to be coated (b) Preheat  the  cleaned  and  masked  parts  to 175-2000 F (79-930 C) (c) Apply    the    nickel    alloy    bond    coat    onto designated areas to a thickness of 0 002-0 007 in (0 05- 0.18 mm) (d) As soon as spraying operations are started, introduce  a  stream  of  air  onto  the  part  being  coated  to maintain a part temperature not to exceed 2500    F (121 C)Maintain  cooling  air  blast  throughout  all  coating operations (e) Apply the aluminum bronze coating onto the designated areas to a total thickness of 0.025-0 035 Inch (0 64-0 89 mm) or to a  total  thickness  required  to  meet drawing requirements after finish machining. (f) The   spray   coating   must   impinge   on   the surface   to   be   coated   at   an   angle   of   75-105   degrees (1.31-1 83 radians) (g) Remove   masking   In   a   manner   that   will avoid damage to the sprayed coating. (h) Impregnate    the    aluminum    alloy    coating completely with an approved silicone resin coating Completely impregnation is accomplished when, 30 minutes   after   application,   resin   is   still   present   on   the coated surfaces Air dry the silicone resin coated parts for 55 to 65 minutes and then bake the coated parts at 140- 1600 F (60-730 C). holding at heat for 55 to 65 minutes followed by heating   to   450-5000   F   (232-2600   C),   holding   at   the selected  temperature  within  15°  F  (80  C)  for  55  to  65 minutes, and cooling In air. e QualityThe sprayed coating shall be adherent to the basis material and shall have a uniform surface  free  from  blisters,  chips,  or  other  objectionable imperfections     not     readily     removable     by     finishing operations (1) Examination  shall  show  the  coatings  to  be free  from  cracks  and  massive  oxides,  and  excessive porosity (2) Coating shall be free from grit particles and contamination  at  the  Interface  between  the  coating  and substrate f Rejections.  Parts  on  which  the  sprayed  coating does     not     conform     to     the     requirements     of     this specification,   or   to   authorized   modifications,   shall   be subject to rejection g Approved Equipment and Materials The following equipment and materials are approved for use under requirements of this specification (1) Equipment Any model Metco gun (2) Coating Alloys (a) SF aluminum (item 20, appx B) (b) AVCO    silicon    aluminum    (item    16, appx B) (3) Silicone resin alloys. (a) Silicone Resin (item 18, appx B) (b) Silicone Resin (item 17, appx B) (c) Silicone Resin (item 19, appx B) Change 4    14-9/(14-10 blank)