Formation of TiN coatings by air plasma spraying

Titanium nitride (TiN) coatings were obtained on the surface of 12Kh18N10T steel by air plasma spraying (APS) of TiN powders using an arc plasmatron made by the authors. The plasmatron has a node of circular input and gas-dynamic focusing of the powder and the output apertures of the nozzle-anode are made in the form of rectangular narrowing-expanding channels (No.34334 RK: IPC H05H 1/42). A study of operation modes of a plasmatron for spraying of powder coatings was carried out. The structural-phase state, microhardness and wear resistance of TiN coatings were systematically investigated. The optimum APS operating mode for deposition of TiN powder was determined: current 250 A, voltage 68 V, argon gas flow 34 L/min, spraying distance 150 mm. To reduce the oxidation of TiN powder in the APS process, a method of creating a nitrogen environment at the outlet of the anode nozzle, nitrogen flow rate 2.3 bar was used. The results of structural analysis showed that TiN is the main phase of the coating. The mechanism of formation of TiN structures was characterized by analyzing SEM results of TiN coating surface morphology and TiN droplets sprayed on the surface of the sample. The results showed that the TiN(1) coating has better wear resistance than the TiN(2) and TiN(3) coatings. The cross-sectional and longitudinal microhardness of the TiN coating was investigated. The highest cross-sectional hardness of TiN coating is 1250 HV0.1, which is in accordance with mode 1

Effect of the PEN/C surface layer modification on the microstructure, mechanical and tribological properties of the 30CrMnSiA mild-carbon steel

As a result of plasma-electrolytic nitrocarburizing 30CrMnSiA carbon steel (ferrite-perlite grade), there was a change in the elemental and phase composition, as well as the surface layer microstructure (40 ÷ 45 microns thick from the surface). A formation of Me23(CN)6 carbonitrides, FeN nitrides, Fe3C - (Fe, Cr)3C carbides and an increase in dislocation density within –phase (tempered martensite crystallites), high-temperature lamellar martensite were observed. As a result of PEN / C exposure for 7min. At 750 ◦C there is a reduction of friction coefficient and wear rate, what is connected with finely dispersed secondary phases FeN, (Fe, Cr)3C, Me23(C, N)6 formation. Thus, there is an 2,5 ÷ 3,3 times increase in hardness of 30CrMnSiA carbon steel samples