ARMY TM 5-6115-612-34 NAVY AG-320B0-MME-000 (b) Preheat  cleaned  and  masked  part  to 175-200°  F  (79-93°  C)  using  plasma,  flame,  or  oven Check  temperature  with  infrared  thermometer  gun  or equivalent (c) Spray the molybdenum powder   coating   (Item   78,   appx   B)   onto   designated surfaces to a thickness required by engineering drawing (d) The  molybdenum  spray  must  impinge on   the   surface   to   be   coated   at   an   angle   of   75-105 degrees (1 31-1 83 radians) (e) Remove  masking  In  a  manner  as  will avoid damage to the sprayed coating (f) The part number, serial number, coating  thickness,  date  sprayed  and  any  discrepancies noted during the coating process must be recorded when the parts being processed are serialized parts. (g) Coated   areas   shall   be    rotary    wire brushed  to  remove  any  loose  particles  on  the  surface and edges of coating e Molybdenum  Removal.  If  required,  the  sprayed molybdenum  coat  may  be  removed  by  masking  areas not  coated  and  removing  plasma  sprayed  molybdenum by grit blasting using 120 grit aluminum oxide at 60 to 80 lb   (414   to   552   kPa)   air   pressure   or   other   methods approved by Materials Research and Engineering. f Quality Perform In-process inspection as follows (1) Parts  and  coupons  shall  be  inspected  for adequate  surface  preparation  and  cleanliness  just  prior to coating. (2) The  sprayed  coating  shall  be  adherent  to the base material and shall have a uniform surface free from blisters, chips, or other objectionable imperfections. (3) Metallographic examination The lest specimen  shall  be  metallographically  examined  at  100 diameters for the following (a) Freedom of cracks (b) Freedom  from  separations  within the coating or between the coating and the base metal (4) Coating   thickness.   The   coating   thickness shall     be     measured     for     conformance     to     drawing requirements (5) Hardness   Surface   hardness   shall   be   not lower  than  81  0  HR30T  Surface  on  which  hardness  is determined  should  have  0.003-0  005  In  (0  076-0  127 mm)  removed  by  machining  or  polishing  to  provide  a smooth surface. (6) Minimum  bond  strength  shall  be  2500  psi (172 kPa)A bond test specimen will be checked on Initial production startup and on request thereafter g Approval    To    assure    adequate    performance characteristics,  parts  sprayed  In  accordance  with  this specification  shall  be  approved   by   Quality   Assurance unless such approval Is waived. h Rejection  Parts  on  which  the  sprayed  coating does     not     conform     to     the     requirements     of     this specification,   or   to   authorized   modifications,   shall   be subject to rejection i Approved Equipment The  following  equip-  ment Is    approved    for    use    under    requirements    of    this specification D-6   Flame Spray Coating - Aluminum Alloy (4043). a Scope (1) Type This specification covers the procedure  for  flame  spray  deposition  of  an  aluminum alloy (2) Application  Primarily  to  provide  abradable coating  to  reduce  clearance  between  compressor  rotor blade tips and sealed compressor case wall b Applicable    Documents    The    latest    Issue    of Aerospace Material Specifications (AMS) shall apply (1) Engineering Material Specifications • Nickel-aluminum  composite  (item  11, appx B) • Steel wire, corrosion resistant (item 12, appx B) (2) Engineering Process Specifications • Vapor degreasing (item 4, appx B) • Grit blasting (Item 3, appx B) • Solvent, petroleum (item 5, appx B) • Aluminum alloy wire (Item 14, appx B) 14-6    Change 4