Hello,
Basically flame powder spray is an old technique and there are many newer technologies around nowadays, but these require expensive equipment and the powders used are very specific. I bought my MWA International MAC flame powder spray oxyacetylene torch 7 years ago at an industrial exhibition in Riga from a Rostherne based UK company. The torch can cost around GBP 1000 nowadays. There are many other torch manufacturers on the market, but you must remember that it is "flame powder spray" and any other term may mean an other technology which requires a different powder too. These powders have round particles and they fuse ideally without making pores or bubbles, hence it is an ideal material for building up hopeless parts for plating. MWA International were also selling Nickel powders -- they can be different hardness from HRC 15 to HRC 60 and different composition. For building up parts you only need HRC 15 powder. Since then I have been using UTP powders, e.g UTP HA-6315G (Ni, Cu,Si,B,C) -- it is 170 -- 240 HV (Vicker's Hardness) and is easily machinable and flowing well. You need to sandblast the part clean shortly before flame powder spraying. The trick is to heat the part and start applying a thin coat of powder (it goes through the oxygen channel from a little cup on the torch) before your steel or cast iron part gets blue -- if you overheat, the coating will not adhere. Likewise if the part will be too cold the process will not go properly. It takes some experience and patience. Sometimes if intricate parts need joining you can build up each part, machine them and then put together and spray build up like they have always been -- one part. For building up worn shafts I use UTP HA-5, it is Ni, Cr, B, Si, Fe, C and is around HRC 40 - 45 with good antiseize properties. I have been building up worn steel brake drums, shafts, welding cast iron cylinders, frame lugs, worn brake pedals, etc. This technology is a real restorer's Godsend if you use your imagination and practice the skills.
Good luck.
Before repair 1
Before repair 2
After repair 1
After repair 2