Effect of Heat Treatment Conditions on Micro Structure of Cast Iron Coatings Sprayed by HVOF Spraying

Abstract

Steel materials have been replaced with light material for the purpose of reducing weight of products in many industry fields. As for these light metal materials, the wear resistance and heat resistance are inferior to the steel material. The compound with the steel material is given to one of the methods for the solution of this problem. In this study cast iron powders were sprayed on the aluminum alloy substrate using HVOF spraying method to produce composite material with excellent wear resistance property. Cast iron powder made by gas atomized method was used as spray materials and Al-Mg alloy (JIS A5083) was used as a substrate. In thermal spraying deposition efficiency shows a decreasing trend when spray distance increases. With increasing thermal spray distance, micro Vickers hardness value decreased and mass loss of Suga type abrasive wear test and ball-on-disk wear test increased. In blast erosion test, the mass loss of their coatings increased with increasing blast angle each spray distance and in each blast angle, the mass loss of coating sprayed by distance 200 mm was smaller than other coatings. Spray material and sprayed coatings were heat-treated to examine the influence of heat treatment condition on their micro structure. Heat treatment was carried out using electric furnace in the vacuum atmosphere of 1 � 10 � 3 Pa. The heating rate was 10 K/min and holding temperature was changed between 673 and 1273 K every 200 K. The graphite phase was observed at the processing temperature of 1073 K or more. Powder that had been heat-treated at 1073 K was then sprayed under the same conditions. Cast iron coating included graphite phase was obtained by using the thermal spray material heat-treated by 1073 K. [doi:10.2320/matertrans.47.1658]