Improving low-carbon steel surface layer hardness through modifying coating plasma treatment

Abstract

The purpose of the paper is to conduct research to assess the possibility of increasing the St 3 steel surface layer hardness under plasma heating of surface coating containing PR-N80H13S2R powder alloy. Research methods involve measuring macrohardness using a stationary device HBRV-187,5. Microhardness is measured using the DuraScan G5 device with an automatic fingerprint reading system. The theoretical methods include the analysis of chemical composition of coatings. As a result coatings are divided into 2 groups: for furnace chemical-heat treatment and plasma surface reflow. Calculation methods include statistical processing of experiment results and building dependencies. The depth of the modifying layer (depending on the processing method) is 1 mm under chemical and thermal treatment, and 2 mm under plasma reflow. Measurement results of surface macrohardness have shown that the resulting coating from PR-N80H13S2R+Cr₂O₃+NH₄Cl mixture features a more uniform distribution of high surface hardness (31-64 HRC according to the Rockwell method of non-destructive testing of material hardness), if the coating consists from PR-N80H13S2R alloy only the surface hardness varies in a larger range (15-60 HRC). The studies of the surface layer cross-section microhardness have shown that the diffusion region made of PR-N80H13S2R+Cr₂O₃+NH₄Cl powder mixture features a uniform hardness (450-490 HV). Coating of the PR-N80H13S2R alloy increases hardness in the depth of the melted area (from 300 to 600 HV) and decreases it sharply in the zone of thermal influence (210-170 HV). The use of the powder alloy PR-N80H13S2R as the main component of coating applied to the steel 3 surface under plasma treatment results in the formation of a modified surface layer of high hardness.