Porous metal coatings using shockwave induced spraying

A method for producing a porous coating on a substrate;

• the method comprising:
• providing a particulate material having a given melting point and a given particle size distribution;
• providing a ShockWave Induced Spraying (SWIS) device comprising a tubular chamber with a generally uniform cross-sectional area having a spraying end and a gas inlet opposite the spraying end, and a gas supply fluidly connected to the gas inlet, where the gas supply contains a gas at a pressure higher than a pressure within the tubular chamber, the SWIS device comprising:
• a first controllable valve located between the gas supply and gas inlet for regulating a flow of gas into the tubular chamber from the gas inlet;
• a powder feeding system having an outlet operatively connected to the tubular chamber downstream of the gas inlet to feed the particulate material into the tubular chamber;
• and
• a heater for preheating the particulate material to a preheat temperature prior to delivery to the tubular chamber,
• maintaining the gas in the gas supply at a temperature lower than the melting point of the particulate material;
• directing the spraying end of the spraying device towards the substrate;
• feeding the particulate material within the tubular chamber in a controlled manner;
• generating a pressure wave traveling along the tubular chamber from the gas inlet to the spraying end by opening and closing the controlling valve, the pressure wave accelerating the particulate material longitudinally within the tubular chamber towards the spraying end;
• and
• projecting the particulate material through the spraying end onto the substrate at an average particle velocity to coat the substrate;
• wherein, an amplitude and a frequency of the pressure wave, the preheat temperature, a feeding rate of the particulate material, and the particle size distribution of the particulate material are chosen to produce a coating on the substrate having a porosity of at least 10%.