Cathodic Cage Plasma Nitriding Research Articles

Enhancement of hardness and tribological properties of AISI 321 by cathodic cage plasma nitriding at various pulsed duty cycle

AISI 321, an austenitic stainless steel, has high corrosion and temperature resistance, making it useful for aerospace and chemical processing. Cathodic cage plasma nitriding (CCPN) is a versatile technique that enhances material surface characteristics. This study aims to investigate the effect of the pulsed duty cycle from 10 % to 60 % on microhardness and tribological properties through CCPN treatment. The X-ray diffraction (XRD) analysis indicates a noticeable shift in the γ-phase towards the lower 2θ angle originating from the expanded austenite phase γN by the lattice expansion at the lowest duty cycle. Nitriding at the lowest duty cycle reduced the average crystallite size from 68 nm (untreated) to 4.5 nm, while increasing the duty cycle led to a decrease in micro-strain. The surface microhardness of the sample that underwent the lowest duty cycle improved to 1288 HV0.01 compared to the untreated sample (210 HV0.01). Moreover, the lowest wear rate is observed for the sample nitrided at a low-duty cycle, which agrees with hardness and strain behavior. The results show that the variable pulsed duty in CCPN can improve the surface hardness and tribological properties of AISI 321, particularly at low-duty cycles.

Improved corrosion resistance and cytotoxicity of nickel‐based alloy using novel plasma processing technique

AbstractIn this study, we address challenges in the biocompatibility of nickel‐based (NiCr) alloys, prevalent in the dental industry, due to toxic metal ion release impacting corrosion resistance and cytotoxicity. Employing magnetron sputtering and cathodic cage plasma nitriding (CCPN), a duplex plasma treatment (DPT) is introduced to the NiCr alloy. The novel approach enhances surface morphology, notably reducing ion leakage compared with untreated samples. Specifically, the CCPN‐TiN‐treated sample significantly improves corrosion resistance and minimizes metal ion leakage. This transformative DPT emerges as a promising solution for surface modification, particularly mitigating toxic ion leaching in aggressive electrolytes. This research demonstrates a major stride in enhancing NiCr alloy biocompatibility, emphasizing the vital role of innovative surface modification techniques for biomedical applications and challenges.

Improved dry sliding wear behavior of TA1titanium by low-temperature plasma nitriding by CCPN method

Cathodic cage plasma nitriding (CCPN) has been proven a promising technique to improving titanium’s poor wear resistance at a relatively lower temperature. Nonetheless, less attention has been paid to the performance of the treated sample at the cathodic potential by CCPN process, mostly on the sample at the floating potential. It has been demonstrated that a nitrogen diffusion layer is formed other than compound layer at the cathodic potential, which is beneficial to improve the bearing-load capacity and adhesion strength between the modified layer and the substrate. In this study, a cathodic cage in combination with pulsed-biased system has been used to realize nitriding of TA1 titanium at the cathodic potential below 660 °C. The influence of pulsed current and treatment time on the resulting surface microstructure and wear performance when sliding against Si3N4 balls were studied. Results showed that with the increasing pulsed current and prolonged processing time, the nitride layer thickness, hardness and roughness also increase. Additionally, although the anti-wear resistance is considerably improved through nitriding treatment compared to untreated TA1 titanium, and there are still differences between the samples prepared under different nitriding parameters. Lastly, the optimum pulsed current and processing time of the CCPN process that provide the best tribological characteristics are determined.

Time-resolved plasma diagnostics of cathodic cage plasma nitriding system with variable pulsed duty cycle and surface modification of plain carbon steel

Cathodic cage plasma nitriding (CCPN) is an efficient technique to improve the surface properties of metallic and non-metallic materials, including steels. Usually, CCPN is powered by pulsed voltage sources due to additional control of the nitrided layer's thickness and composition as well as the discharge transition to the arc region can be controlled by varying the pulsed duty cycle. As the behavior of pulsed plasma varies with time, it is important to monitor variation in plasma parameters by using time-resolved plasma diagnostics. Unfortunately, the fundamental time-resolved diagnostics of such discharges are still very limited. Here, we report time-resolved measurements of current, voltage, plasma emission, space, and time-resolved emission from a single hole in the cathode as a function of pulsed duty cycle (15–75 %) at constant total current. The results show that the electron temperature is higher if a higher peak current and the shortest 15 % pulsed duty cycle are used. The results obtained from plasma diagnostics are confirmed by treatment of plain carbon steel samples in identical conditions and found that the best hardness, wear, and corrosion resistance is obtained at the lowest pulsed duty cycle. The study suggests that plasma generated at a low pulsed duty cycle and a higher peak discharge current exhibits higher electron temperature and less fluctuations in plasma emission which are more efficient in attaining high surface hardness, better wear, and corrosion resistance to nitride plain carbon steel.

Tribological Behavior of SINTER30 Steel Subjected to Duplex Treatment

Plasma nitriding has been extensively used to improve materials’ surface and mechanical properties using conventional plasma techniques. However, this process generally results in a nonuniformity of the properties. In the cathodic cage plasma nitriding (CCPN), the plasma is active only on the surface of the cathodic cage, eliminating inherent defects of conventional plasma nitriding. Herein, a duplex treatment, CCPN and TiN deposition, is used on SINTER30 tool steel for the first time. Vickers microhardness tests, X‐ray diffractometry, Raman scattering spectroscopy, and scratching tests characterize the samples. The results show that TiN post‐coating attains higher surface hardness. All the groups increase their microhardness properties when compared with nontreated substrates. The prior treatment of plasma nitriding assists hardening of the substrate surface. The best condition is obtained when the sample is placed inside the titanium cage and positions directly on the sample port, with simultaneous duplex treatment. When the substrate passes through this simultaneous duplex process, peaks corresponding to Fe3N and TiN are observed at Raman spectra. Suitable TiN layers improve the film adhesion, which is correlated to the system's load‐bearing capacity.

Tribo-Mechanical Behavior of Films and Modified Layers Produced by Cathodic Cage and Glow Discharge Plasma Nitriding Techniques

Two surface modification techniques, the glow discharge plasma nitriding (GDPN) and the cathodic cage plasma nitriding (CCPN), were compared regarding the mechanical and tribological behavior of layers produced on AISI 316 stainless-steel surfaces. The analyses were carried out at the micro/nanoscale using nanoindentation and nanoscratch tests. The nitriding temperature (°C) and time (h) parameters were 350/6, 400/6, and 450/6. Morphology, structure, and microstructure were evaluated by X-ray diffraction, scanning electron and optical interferometry microscopies, and energy-dispersive X-ray spectroscopy. GDPN results in stratified modified surfaces, solidly integrated with the substrate, with a temperature-dependent composition comprising nitrides (γ’-Fe4N, ε-Fe2+xN, CrN) and N-solid solution (γN phase). The latter prevails for the low treatment temperatures. Hardness increases from ~2.5 GPa (bare surface) to ~15.5 GPa (450 °C). The scratch resistance of the GDPN-modified surfaces presents a strong correlation with the layer composition and thickness, with the result that the 400 °C condition exhibits the highest standards against microwear. In contrast, CCPN results in well-defined dual-layers for any of the temperatures. A top 0.3–0.8 µm-thick nitride film (most ε-phase), brittle and easily removable under scratch with loads as low as 63 mN, covers a γN-rich case with hardness of 10 GPa. The thickness of the underneath CCPN layer produced at 450 °C is similar to that from GDPN at 400 °C (3 µm); on the other hand, the average roughness is much lower, comparable to the reference surface (Ra ~10 nm), while the layer formation involves no chromium depletion. Moreover, edge effects are absent across the entire sample´s surface. In conclusion, among the studied conditions, the GDPN 400 °C disclosed the best tribo-mechanical performance, whereas CCPN resulted in superior surface finishing for application purposes.

Effect of hydrogen on microstructure and mechanical properties of plasma-nitrided pure titanium by cathodic cage plasma nitriding

Surface modification technologies have been applied for the improvement of surface properties, and low temperature nitriding in the mixed N2-H2 atmospheres by cathodic cage plasma nitriding (CCPN) is identified to be an effective way to enhance the mechanical properties of Ti and its alloys. However, little attention was paid on the absorbed H2 in the nitrided specimen under different H2 proportion and the consequent deleterious influence. In this paper, the influence of different H2/(N2 + H2) ratio on microstructure of the nitrided Ti specimens by CCPN were investigated by XRD, EDX, SEM, respectively. And the surface structure of the compound layer is consisted of an outer layer of δ-TiN over the inner layer of ε-Ti2N, formed on the top of diffusion layer consisting of mainly of α-Ti solid solution enriched with nitrogen. It is found that the thickness of compound layer on Ti increases with the introduction of H2. And the N-rich top layer of TiN layer with coarse grain structure is resulted by the combined effect of the introduction of H2 and the plasma action. The surface mechanical properties of nitrided layer were also measured by microhardness tester and tensile test. The results show an average surface hardness of 900 HV0.2–1100 HV0.2 of the nitride surface compared to that of Ti (200 HV0.2 in average). And the surface hardness of nitrided Ti samples increases with the increasing H2 concentration. However, the tensile properties are badly deteriorated independent of hydrogen concentration with the introduction of H2 due to the generation of titanium hydride during nitriding process.

Wear and corrosion studies of duplex surface-treated AISI-304 steel by a combination of cathodic cage plasma nitriding and PVD-TiN coating

This work aims to improve the surface properties of AISI-304 austenite stainless steel by using duplex treatment of cathodic cage plasma nitriding (CCPN) and PVD-TiN, and the results are compared with individual treated samples. This combination of treatments is used to improve the inherent drawbacks of individual PVD deposited TiN, such as voids, cracks, and detachment of hard layer from steel due to significant differences in the hardness of steel and hard layer. The hardness of steel (1.9 GPa) is improved to 17 GPa, 12 GPa, and 22 GPa by using only TiN, CCPN, and duplex treatment. The only TiN deposited sample shows the formation of layer with intense diffraction peaks along (311) and (400) orientation, and its orientation changed with intense peaks along (111), (200), and (220) by using duplex treatment, which increases the hardness. Furthermore, the wear resistance is improved by all treatments, specifically by using duplex treatment. While using a ball-on-disc wear tester, the TiN layer is not detached from the substrate in the duplex treated sample, in contrast with the only TiN sample. Furthermore, the corrosion rates are reduced by using the duplex treatment and the appliance of plasma nitriding before the TiN fills the voids and cracks in layer, and thus, the duplex layer effectively prevents steel against corrosive environment. This study suggests that combining these treatments improves surface hardness, wear resistance, and corrosion resistance.

Combined plasma treatment of AISI-1045 steel by hastelloy deposition and plasma nitriding

AISI-1045 steel is medium strength steel, and it needs surface modification to use in machine components. The surface properties of steel can be improved by plasma nitriding. The nitriding performance can be upgraded by introducing special alloying elements (nitride forming elements such as chromium, molybdenum), which have a strong affinity with nitrogen. Here, the combination of cathodic cage plasma nitriding (equipped with hastelloy cathodic cage, containing nitride forming elements) and conventional plasma nitriding is used to improve the surface properties. Thus, it is used to deposit such alloying elements, and subsequent plasma nitriding is performed to cause nitrogen diffusion to improve the coating adhesion and hardness gradient formation. The substrate hardness (346 HV) is increased up to 982 HV, 1426 HV, and 1692 HV by hastelloy deposition and post-nitriding at 400 and 450 °C, respectively. Additionally, the duplex treated samples show a favorable hardness gradient. The treated samples show the formation of iron nitrides Fe4N, Fe2−3N, chromium, and nickel phases. The voids and pores have appeared on the hastelloy deposited sample, removed by post-nitriding. The wear resistance is significantly improved by duplex treatment. The duplex treatment reported here can be used effectively to improve the surface hardness and wear resistance of AISI-1045 steel. Additionally, a single processing unit is required, needs low-processing temperature, surface uniformity, the whole processing time is relatively short, and the compatibility of this system with the industry proposed that this work would be helpful for the industrial requirement.

Comparative study of PVD titanium nitride coating with cathodic cage plasma nitriding of austenitic 201 stainless steel for enhanced tribological properties

Comparative study of PVD titanium nitride coating with cathodic cage plasma nitriding of austenitic 201 stainless steel for enhanced tribological properties

Hybrid TiN-CCPN coating of AISI-201 stainless steel by physical vapor deposition combined with cathodic cage plasma nitriding for improved tribological properties

The poor mechanical properties of AISI 201 stainless steel under harsh environment limit its uses in modern building structures, automobiles and aerospace industry. Various technologies, such as physical vapor deposition (PVD) and cathodic cage plasma nitriding (CCPN) at different temperatures, are being used to reduce wear and tear of metals but the optimal method with acceptable results is still under development. In this paper, a novel duplex surface coating method, coupled with DC pulsed CCPN, was used to develop anti-wear and anti-corrosive TiN-coating over AISI 201 stainless steel. The CCPN, TiN coatings over AISI 201 stainless steel were performed in alternative manner and characterized for surface hardness, surface morphology, wear rate, chemical composition and erosion rate. XRD analysis revealed the formation of iron nitride and titanium nitride planes in the coated samples when compared with base materials. The TiN coated coupons exhibited reasonably good tensile strength, which increased manifold on CCPN treatment. The CCPN treated TiN coated coupons showed very low wear rate, wear volume and erosion rate among all the tested samples. Scanning probe microscopy was used to study the erosion rate and topology of the base and coating coupons under different water jet velocities. The erosion rate of base coupon at a jet velocity of 5 m/s was measured about 1.27 mm/year, which fell to 0.25 mm/year after duplex coating. The results show that duplex coatings, when applied in the proper order, can improve mechanical qualities by reducing wear rate, erosion rate, and wear volume.

Corrosion Resistance and Microstructural Evaluation of a Plasma Nitrided Weld Joint of UNS S32750 Super Duplex Stainless Steel

Super duplex stainless steel (SDSS) combines corrosion resistance and mechanical properties, interesting to applications in the oil extraction industry. In this process, wear between the tools friction and rocky materials occurs with SDSS pipes. Due to the low tribological properties, plasma nitriding process is applied to provide a surface layer with excellent wear resistance and without significant losses in corrosion resistance. Here, conventional plasma nitriding (CPN) and cathodic cage plasma nitriding (CCPN) techniques were compared to modify SDSS surface. Before and after passing by these two nitriding processes, welded joints (WJ) were subjected to a microstructural and corrosion resistance evaluation. Aiming to characterize the final product obtained, it was used characterization techniques, such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that using the CPN technique, at 400°C, was responsible for providing greater resistance to corrosion, when analyzing the result of potentiodynamic polarization — jpassivation = 2.60x10-5 A.cm-2 and Epite = 0.83 V than the CCPN technique when applied to the SSDS, and this was attributed to the formed diffusion layer, which is composed of the expanded austenite and ferrite phases.

New technique for deposition and thermochemical treatment of small parts with complex geometry applied to machining inserts

Cutting tools, such as machining inserts, which in addition to having a complex geometry need to handle different demands on more than one face during their application, stimulate investigation for new coating techniques. Even though many hard film deposition techniques are well accepted or even established among researchers and industries, these processes still need to meet a limitation that requires the repositioning of the sample for new treatments in order to cover all of its surfaces. This paper proposes a new methodology for coating deposition on complex geometry pieces, through a structure for three-dimensional plasma treatment, using a Rotary Cathodic Cage Plasma Nitriding (RCCPN). TiN films were deposited on cemented carbide inserts applied in machining processes using the RCCPN technique. The plasma parameters were kept constant and deposition time was the only variable input. The deposited films were characterized by SEM, EDS, XRD, and Vickers microhardness. It was observed that the RCCPN technique was useful in producing a uniform TiN layer in all insert surfaces, with a thickness proportional to deposition time.

Internal coating of pipes using the cathodic cage plasma nitriding technique

This work confirms the possibility of the application of a plasma nitriding technique, with a cathodic cage, for lining pipelines through the deposition of thin nitride films. The process using the cathodic cage technique is based on the simultaneous use of multiple hollow cathode effects. Thus, is possible to obtain a uniform lining promoving an increase in the hardness and corrosion resistance of treated samples, with elimination of edge and shadow effects in the nitrided layer. The cage is made of austenitic stainless steel AISI 316, containing a removable lid and holes with well defined diameters and distances between adjacent holes. Combining the tension and pressure in the process results in the possible occurrence of the hollow cathode effect in all holes. The material removed by sputtering is transferred to the workpiece surface. In this application, the cage in which a cathodic potential is applied is surrounded by the samples to be treated (glass tubes and 316 steel plate). The XRD analysis confirmed the deposition of iron nitrides in the presence of phases that are also seen in samples treated on the inside of the cage, which allows simultaneous treatment of internal and external samples in relation to the cage.

Plasma nitriding of AISI M2 steel: performance evaluation in forming tools

ABSTRACTPlasma nitriding is a thermochemical treatment to improve the surface properties of metallic materials, such as mechanical and tribological properties. The aim of this study is to compare the nitriding performance of conventional plasma nitriding (CPN) and cathodic cage plasma nitriding (CCPN) for AISI M2 tool steel at various temperatures (400°C, 450°C and 500°C). The forming tool is also processed in identical conditions, and its productivity performance in the manufacturing of nails for civil construction is also evaluated. The highest hardness is achieved while processing samples at 400°C, and better productivity performance while treating samples at 500°C, both in CPN and CCPN. Notably, the hardness and productivity performance achieved in this study, particularly using CCPN is significantly higher than the forming tool provided by the factory in which conventional processing techniques were used, and thus it suggests the effectiveness of CCPN in wide-scale industrial applications in forming tools.

Surface modification of M2 steel by combination of cathodic cage plasma deposition and magnetron sputtered MoS2-TiN multilayer coatings

Titanium nitride (TiN) is a good choice for the improvement in surface hardness of high-speed steel. Unfortunately, it has low adhesion with substrate and exhibits high friction coefficient; as a result it does not provide sufficient protection against sliding wear in metal-to-metal contact. The adhesion problem can be removed by nitriding process, whereas friction coefficient can be reduced by solid lubrication coating. In this study, an attempt is made to synthesize TiN hard coating as well as solid lubrication coating of molybdenum disulfide (MoS2) using magnetron sputtering, along with substrate pre-treatment by cathodic cage plasma deposition using titanium cathodic cage. The cathodic cage plasma nitrided sample exhibits significantly higher surface hardness, which reduced by solid lubrication coating. The nitrided sample depicts the presence of iron nitrides, TiN and nitrogen diffused martensite phases, whereas coated samples shows the presence of MoS2 and TiN phases. The friction coefficient and machining temperature are dramatically reduced by lubrication coating. This study recommends that the use of cathodic cage plasma nitriding using titanium cathodic cage is beneficial for improved surface hardness, and addition of solid lubrication coating is beneficial for reducing the coefficient of friction and machining temperature by scarifying hardness. As, both the systems are already proven to be appropriate for industrial-scale uses, thus results from this study can be applied for industrial-scale application.

Enhanced wear and corrosion resistance of AISI-304 steel by duplex cathodic cage plasma treatment

The austinite stainless steel is widely employed in several industries due to exceptional corrosion resistance. Unfortunately, their use is restricted due to low surface hardness and poor wear resistance. The aim of this work is to improve the wear and corrosion resistance of AISI-304 steel using duplex cathodic cage plasma nitriding method. The duplex treatment is carried out in a two-step process using an alternative combination of aluminium and austinite stainless steel cathodic cages, with a process duration of 1 and 4 h, respectively. The results of duplex treatment samples (first processed by an aluminium cathodic cage (pre-Al CC) and in reverse order (post-Al CC)) are compared with single aluminium, and austinite stainless steel cathodic cage treated samples. The hardness-indentation depth profile illustrates the significant improvement in hardness by post-Al CC nitrided sample, and a strong dependence on processing order is observed. The aluminium nitride is found to be leading phase in the post-Al CC sample, which is probably responsible for significant hardness improvement. Particularly for post-Al CC treated sample, the wear rate and corrosion rates are dramatically reduced by processing. This study shows that duplex treatment with a particular processing specific order is highly beneficial for mechanical, wear and corrosion properties of the sample under consideration. The use of a single processing unit for both treatments, better surface uniformity, low-processing temperature, short combined treatment time and industrial compatibility of the system suggest the suitability of the technique for industrial applications.

Effect of pulsed current on cathodic cage plasma nitriding of non-alloyed steel

The cathodic cage plasma nitriding (CCPN) is an efficient and cost-effective surface modification technique, extensively used in last two decades. The effectiveness of CCPN is dependent on several control parameters and the objective of current research is to examine the effect of pulsed current on CCPN efficiency. The samples of non-alloyed steels are nitrided in fixed processing conditions while using variable pulsed current. The processed samples are analyzed by micro-hardness test, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS) and ball-on-disc wear tester. The corresponding plasma parameters (such as electron temperature and nitrogen active species generation) are analyzed using optical emission spectroscopy (OES). The hardness and wear resistance is found to be significantly enhanced by increasing the pulsed current. The processed samples contain iron nitrides phases whose intensity increases with increase in pulsed current. The results from surface analysis show a good correlation with the results obtained from OES. This study clarifies the contribution of pulsed current on the nitriding performance and plasma reactivity in CCPN system in a comprehensive manner. The results are compared with the previous reports on various systems.

Comparative study of surface modification techniques through average flank wear in high speed steel tools coated with thin TiN film

Hard coatings are usually applied to improve high speed steel (HSS) tools performance. However, to achieve this aim, a good adhesion between coating film and substrate is necessary. The coating failure, associated to the lack of adhesion to the substrate, can lead to tool premature wear, reducing its efficiency. The surface modification can improve the coating film adhesion levels by modifying substrates surface roughness, and then, ensuring better anchorage of the deposited layer. In this research two techniques of superficial modification, planar sputtering and chemical polishing, were compared. The sputtering uses plasma application, where cations formed in the reactor collide with samples surface, removing material from it. For chemical polishing, it was used acid and alkaline solutions. After surface treatments, all roughness levels were measured using a roughness tester. The Cathodic Cage Plasma Nitriding (CCPN) technique was used to deposit a TiN film on tools surface. Then, X-ray diffraction, Vickers microhardness and SEM tests were carried out to verify the presence of deposited film, as well as its thickness and mechanical properties, and then, machining tests with SAE 1045 steel where performed, applying the coated tools. Optical microscopy was carried out to track average flank wear up to 0.3 mm, characterizing the end of tool life. It can be observed that all the coated tools obtained an increase in its life, registering the variances according to the different roughness profiles. The best results were verified for chemical polishing with acid solution treatment condition, as it allowed longer machining time with less flank wear.

Deposition of fine copper film on samples placed internally and externally to the cathodic cage

Abstract The cathodic cage plasma nitriding technique is used for thin film deposition. As such, the hollow cathode effect on cage holes is directly related to deposition efficiency. The objective of this work is to study the influence of the cathode length-to-diameter ratio in the deposition of fine copper films on samples placed internally and externally to the cathodic cage, in an argon atmosphere, for 3 h at 420 °C. Compositional, transmittance and morphological characterization of films show copper deposition in all treatments. However, it was observed that substrate temperatures during film deposition influence its morphology. As such, the formation of continuous film on internal samples is observed, whereas external samples show uniformally dispersed nanoparticles as well as the absence of dense film on substrates. As far as the length-to-diameter ratio is concerned, the 1.5 ratio presented the highest deposition efficiency.