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AISI-1045 steel is a medium-carbon, medium-strength steel that usually requires surface engineering to be usable in industrial applications. Using the cathodic cage plasma deposition technique, transition metal (Nb, V, W) nitride coating is deposited on this steel using cathodic cage lids of these metals. The hardness of untreated steel (1.8 GPa) is upgraded to 11.2, 12.2, and 9.7 GPa for niobium nitride, vanadium nitride, and tungsten nitride coating, respectively. The elastic modulus, the ratio of hardness-elastic modulus (H/E, H2/E, and H3/E2), and the plasticity factor depict the improvement in mechanical and elastic properties. The sample treated with a niobium cage lid exhibits the Nb4N5 phase, the vanadium cage lid shows the VN phase (along with the Fe4N phase), and the tungsten cage lid consists of W2N3, WFeN2, and Fe4N phases. Among these coatings, the thickness of niobium nitride coating is maximum (1.87 μm), and a low deposition rate is obtained for tungsten nitride coating (0.83 μm). In addition to this coating, a nitrogen diffusion zone (∼60 μm) is also formed beneath the coating, which creates a hardness gradient between the coating and the substrate. The ball-on-disc wear tester shows that niobium nitride coating deposition reduces the wear rate from 19.5 × 10−3 to 8.8 × 10−3 mm3/N m and exhibits excellent wear performance. [ABSTRACT FROM AUTHOR]

The nonalloyed steels are very cost-effective, but their usefulness in numerous applications is imbedded due to low mechanical strength. The strength of several steels can be improved by nitriding; however, nonalloyed steels are not suitable. They can be nitrided by introducing special nitriding alloys (like chromium, aluminum, etc.) during manufacturing or some interlayer deposition, but it is quite expensive. The aim of this study is to improve nitriding capability of nonalloyed steels without any additional treatment. This is done by using alloyed stainless steel active screen in active screen plasma treatment, which provides an adequate amount of chromium to form stable and hard nitrides. The processed samples are characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, pin-on-disc wear tester, hardness tester and potentiodynamic polarization test. [ABSTRACT FROM AUTHOR]

A biomimetic method was used to improve bioactivity of Sr2SiO4. Strontium silicate was obtained by using a combination of techniques such as mechanical activation and reactive sintering, of a powder mixture of strontium carbonate and silicon dioxide. Single phase Sr2SiO4 was obtained after 6 h of mechanical milling of the starting reagents, followed by a uniaxial pressing and a thermal treatment in air at 1200 °C for 6 h. For the biomimetic treatment, samples were immersed in a simulated body fluid (SBF) for 7, 14 and 21 days on a bed of wollastonite powder and were characterized by SEM, EDS, XRD, FT-IR and TEM. For comparison purposes, experiments were also performed without using the bioactive powder bed. Results showed that a bone-like apatite layer was formed on strontium silicate after 21 days of immersion in SBF without a bed of wollastonite and slight layer of Ca, P-rich compound, using a bed of wollastonite powder, corroborating the viability of these oxides to be used as bioactive materials. [ABSTRACT FROM AUTHOR]

Although austenitic stainless steels (ASSs) are known for their superior corrosion resistance properties, the use of such materials in motion contact parts is limited due to their low wear resistance. Previous studies reveal that titanium nitride (TiN) coating of ASS significantly improves its hardness and surface morphology but not the wear resistance due to weak interfacing with the substrate. Since plasma nitriding is a flexible and multifunctional case-hardening process, an attempt was made to improve the wear resistance of TiN-coated AISI-304 stainless steel by subjecting it to pre-treatment by pulsed DC cathodic cage plasma nitriding (CCPN) in the abnormal glow region. The hardness of the TiN-coated steel samples (with and without CCPN pre-treatment) was measured using Vickers micro-hardness tester. This test revealed maximum hardness of 2284 HV after plasma treatment of TiN-coated steel. The untreated TiN-coated steel exhibited 10.6 times lower hardness than the plasma pre-treated TiN-coated steel (CCPN-TiN). XRD analysis of the untreated TiN-coated steel showed strong diffraction peaks of TiN (311) and (400) in the spectrum, whereas plasma pre-treated sample contained dominant peaks of TiN (111), (200) and (220). The ball-on-disk wear tester was used to investigate the wear behavior of the samples. Very small wear rate and friction coefficient were reported for CCPN-TiN-coated steel. The observed low wear rate was probably due to the development of a subsurface (i.e., nitrided surface) on TiN-coated steel during CCPN pre-treatment. [ABSTRACT FROM AUTHOR]