Study of properties of HVOF-sprayed coatings

High velocity oxy-fuel (HVOF) spraying method for deposition of powder coatings and HVOF Tafa System were used. Different commercially produced hardmetal, self-fluxing alloy and stainless steel powders were used. The porosity and structure of coatings were studied. The abrasion-erosion wear testings were carried out and wear resistance of above mentioned coatings was determined. It was shown high wear resistance in conditions of abrasion-erosion wear: HVOF sprayed hardmetal coatings exhibited 10-11 times higher wear resistance than non-coated steel. The influence of spraying material to the porosity and hardness of coatings was studied and the influence of hardness and porosity on wear resistance of coatings was clarified. The mechanism of the wear high velocity thermal sprayed coatings was studied and was shown it similarity to that of hardmetals by high density coatings - at oblique impact erosion wear is caused from microcutting, at normal impact erosion from the direct fracture; by coatings with porosity more 3-5% direct fracture mechanism is dominating.