Hardness and microstructure investigation of steel rod ST 42 coated by chrome steel using wire arc spray coating

Purpose: This research aimed to examine the hardness, surface roughness and microstucture in the Steel Rod ST 42 coated by chrome steel using wire arc spray coating with variations in spraying current of 140, 155, 170 and 180 Ampere. Design/methodology/approach: There was 12 specimens consisting of 3 specimens for each variation of the electric current coating. The specimens were cut to 30 mm in length and 27 mm in diameter; as many as 4 x 3 pieces, each specimen was cut to a size of 30 mm and put on a lathe to be drilled 1 mm deep. The hardness testing employed the Brinell hardness test method. The hardness testing process was followed by microstructure observation and SEM-EDAX testing. Findings: The highest hardness was 110.77 HRB by coated at 155 A and it contained many reinforcing inclusions and larger Cr. The lowest current of 140 A had many porosity holes and partially-melted particles, causing Cr grains did not attach perfectly. The current with 170 A had few inclusions and hence a decrease in hardness and at 180 A consisted of a low carbon content and evenly distributed inclusions and Cr and relatively large grain size, and thus the hardness rose. Research limitations/implications: The material of steel rod ST 42 coated by chrome steel. Practical implications: The variation of current should be prepared wisely in term because it will effect the hardness, surface roughness and microstucture. This research can be improved by varying the voltage, gas pressure, particle velocity, particle temperature, and molten wire width. Originality/value: Simple route of making steel rod ST 42 coated by chrome steel using wire arc spray coating and also the investigation of hardness, surface roughness and microstucture in steel rod ST 42 coated by chrome as the result.