with a Ø2 hole is placed under the platform. The distance between
the plate and nozzle is 160mmand 40mmbetween the
water surface and plate. After spraying,water in the container
is dried and powders are obtained. The splats are collected
on a 30mm×30mm×4mm polished stainless steel substrate,
with a baffle with several Ø2 holes placed between
the nozzle and substrate. The distance between the baffle and
the nozzle is 160 mm, and 40mm between the baffle and
substrate.
The Olympus optical microscope with Olycia v3.0 image
analysis system is used to analyze the shapes and sizes of inflight
particles, morphological aspects of splat formation and
cross-sections of coating. HV1000 metallographic microhardness
instrument is applied to test the micro-hardness
of coating, and Vickers micro-hardness measurements have
been carried out with a load of 9.8 N during 15 s. Then
five points of micro-hardness values in the longitudinal and
transverse directions are measured respectively to calculate
the average micro-hardness. The porosity measured by
the method of grey values is calculated with the average
grey value of eight view fields magnified 50 times from the
originals.