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Demand for higher wear and corrosion resistance components has attracted increasing interest in surface engineering. This line of research develops alternative processes for improving the surface properties of engineering materials. The traditional route seeks the development of new alloys. However, the cost and time associated with these developments become prohibitive in many cases. Currently, the application of plasma-assisted thermochemical treatments has been a technically and economically viable alternative to extend the lifespan of components exposed to severe environments. In this sense, the tooling industry is one of the oldest and most traditional users of plasma-assisted processes, since forming, injection and/or cutting tools are usually subjected to wear and corrosion degradation. Among the various materials used to make tools, we highlight the martensitic stainless steels, which are used in the manufacture of molds and inserts for injection of chlorinated and fluorinated thermoplastic and thermoset polymers. In these applications, martensitic stainless steels are exposed to severe deterioration conditions due to abrasive wear and corrosion by chloride and fluoride ions. Considering the variety of available plasma-assisted thermochemical treatments whose application allows improving metallic materials corrosion and wear resistance, it is a complex task to select the better process and its execution parameters to ensure the maximum performance in operation. In this work, it is proposed a systematic method to aid the process selection task, focused on thermochemical treatments of martensitic stainless steels, which integrates the processing conditions and the resulting microstructure, properties and performance. For this purpose, working envelop for selecting processes and processing parameters were elaborated, that allow qualify and quantify the correlations among each specific plasma-assisted thermochemical treatment (like nitriding, carburizing, nitrocarburizing, etc.) execution conditions, with the resulting properties and performance for treated martensitic stainless steels. In parallel, the genesis of plasma-assisted thermochemical treatments is also described, a bibliometric analysis is carried out on the publications on the subject, and also, a summary description of the surface characteristics of the treated materials is realized.

Corrosion resistance of plasma carburized AISI 420 martensitic stainless steel was evaluated by cyclic polarization test in 3.5% NaCl solution. Two distinct treatment groups were studied with the purpose of evaluating the influence of the carburizing temperature and time on the corrosion behavior of treated material (one at 350–500 °C temperature range for 8, and 12 h times; and other one at 400 °C for 12–48 h time range, and at 450 °C for 4–16 h time range). To support the discussions on electrochemical test results, microstructural characterization was carried out using metallographic analysis and XRD techniques. Microstructural characterization results show that low temperature and short time treatments produce outer layer composed by α′C and Fe3C phases. High temperature and/or long time treatments promote outer layer Cr7C3 and Cr23C6 phases precipitation. Corrosion test results show improved carburized samples resistance, which is related to chromium-carbides precipitation-free outer layer formation. The Cr-carbides formation promotes a reduction on carburized samples corrosion resistance due to depletion of Cr in the solid solution of carburized layer. Finally, by confronting the behavior of untreated and carburized samples, it is verified the potentialities of the low-temperature plasma carburizing to enhance the corrosion resistance of AISI 420 MSS.

This work presents the potential of low-temperature plasma carburizing treatments for improving the cavitation erosion resistance of martensitic stainless steel (MSS). As-hardened AISI 420 MSS samples were treated via dc plasma carburizing at 450 °C for 12 h. The cavitation erosion behaviors were compared with that of an untreated steel sample tempered at 220 °C for 1 h. Cavitation erosion tests were performed with an ultrasonic vibratory apparatus in accordance with the ASTM G32-10 standard. The nominal incubation period of the carburized samples was approximately three times higher than that of the untreated sample (23 h versus 7.8 h, respectively). The cavitation erosion behavior was discussed in terms of mechanical surface properties (hardness (H) and elastic modulus (E)) obtained via the nanoindentation technique and respective H/E, H2/E, and H3/E2 ratios.

The present study is aimed at investigating, by means of an experimental approach, the effect of surface wettability on the frost accretion over horizontal flat surfaces under forced convection conditions. A purpose-built closed-loop wind-tunnel facility was especially designed and constructed to provide a strict control of the psychrometric conditions at the entrance of the test section, and also of the plate surface temperature. An image acquisition system was used to measure the thickness of the frost layer over time. A dataset comprised of >800 experimental data points spanning different surface temperatures (from −20 to −10 °C), air temperatures (from 5 to 16 °C), modified Jakob numbers (from 1.05 to 2.10), and static contact angles (from 60° to 123°) was gathered and used to investigate both the individual and simultaneous effects of key heat and mass transfer parameters on the frost growth rate. A first-principles modelling approach was used together with the experimental data obtained in-house to come up with a semi-empirical fully-algebraic expression for the frost thickness as a function of the time, the supercooling degree, and the surface contact angle. It was found that the proposed correlation was able to predict most of the experimental data points (>90%) for the frost thickness within ±15% error bounds. Insights on early and delayed nucleation were also obtained from the analysis of the experimental data.

In this work the behavior of the austenite phase at the surface of a low-carbon martensitic stainless steel and an austenitic stainless steel subjected to cavitation through ultrasonic vibration tests in liquid phase was studied. Emphasis was given to the behavior of two distinct types of austenite, in the case the reversed austenite of the as-tempered ASTM CA-6NM martensitic stainless steel, and the thermally-stable austenite of the solution-treated AISI 304 austenitic stainless steel. The evolution of phases fraction at the studied surfaces by XRD technique was characterized by two ways. Firstly, cavitation test intercalated with XRD measurements as a function of the test time was carried out. In the sequence, an indirect measurement technique comprising the use of Vickers indentation and controlled material removal by polishing, also intercalated with XRD characterization along the incubation period of both steels was used. This procedure was strong enough to determine the mechanism that precedes the erosive wear defining the incubation-acceleration stages transition and the cavitation-affected depth presenting γ(austenite)→α′(martensite) strain-induced transformation in the material microstructure, measured from the surface of the tested region into the interior of the substrate bulk of each studied steel. Such mechanism covers deformation of the steel matrix and strain-induced transformation of the austenite phase at the surfaces subjected to cavitation, strongly influencing the beginning of the significant mass loss process for both low-carbon stainless steels studied here.

Samples of duplex stainless steel SAF 2507 were low-temperature plasma nitrided to characterize separately, on the surface, the behavior of its ferrite and austenite phases in relation to two competing processes, that is, one caused by enrichment by nitrogen, resulting in possible expansion, and the other caused by the removal of superficial atoms via sputtering, which may lead to the retraction of the studied phases. Since these phases have different different compositions and crystalline structures, of which the diffusivity and solubility of nitrogen in them are dependent, a different response for each type of phase can be expected. In this article, an innovative methodology has been developed to quantify and clarify which effects are predominant in the course of nitriding for each of these phases. The results indicate that phase expansion prevails over sputtering.

During the last decades, researchers have been growing the interest in surface treatment with an antimicrobial agent. Silver nanoparticles (AgNPs) are widely used in biomedical fields due to their potent antimicrobial activity. So, in this study was investigated silver particles (isles) coated on titanium surface for dental and orthopedic application. Silver particles coating process on titanium surface were performed via sputtering that is a plasma-assisted deposition technique with and titanium without treatment was applied as comparing standard. Plasma treatment parameters were optimized so that the result was not a thin film of Ag but dispersed particles of Ag on the Ti-cp surface. The alloy surfaces were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). In order to investigate antibacterial potential Staphylococcus aureus and Escherichia coli have been used at Agar diffusion assay. The results were analyzed by analysis of variance (ANOVA) in order to verify significant difference antimicrobial activity between samples that have shown no difference between the surfaces studied treatments. For silver deposition scattered particles (isles) over titanium surface for a 10-minute treatment, EDS revealed by silver clusters that the particles were not properly scattered onto surface, hence, the low effectiveness in antibacterial activity. Durante las últimas décadas, los investigadores han aumentado el interés en el tratamiento de superficie con un agente antimicrobiano. Las nanopartículas de plata (AgNP) se usan ampliamente en campos biomédicos debido a su potente actividad antimicrobiana. Entonces, en este estudio se investigaron partículas de plata (islas) recubiertas en superficie de titanio para aplicaciones dentales y ortopédicas. El proceso de recubrimiento de partículas de plata en la superficie de titanio se realizó mediante pulverización catódica, que es una técnica de deposición asistida por plasma y se aplicó titanio sin tratamiento como estándar de comparación. Los parámetros de tratamiento con plasma se optimizaron para que el resultado no fuera una película delgada de Ag sino partículas dispersas de Ag en la superficie de Ti-cp. Las superficies de aleación se investigaron mediante microscopía electrónica de barrido (MEB) y espectroscopía de rayos X de dispersión de energía (EDS). Con el fin de investigar el potencial antibacteriano, se han utilizado Staphylococcus aureus y Escherichia coli en el ensayo de difusión en agar. Los resultados se analizaron mediante análisis de varianza (ANOVA) para verificar la diferencia significativa de la actividad antimicrobiana entre las muestras que no mostraron diferencias entre los tratamientos de las superficies estudiadas. Para las partículas de plata dispersamente depositadas (islas) sobre la superficie de titanio para un tratamiento de 10 minutos, EDS reveló al presentar grupos de plata que las partículas no se dispersaron adecuadamente en la superficie, por lo tanto, la baja efectividad en la actividad antibacteriana. Nas últimas décadas, os pesquisadores têm aumentado o interesse no tratamento de superfície com um agente antimicrobiano. Nanopartículas de prata (AgNPs) são amplamente utilizadas em campos biomédicos devido à sua potente atividade antimicrobiana. Assim, neste estudo foram investigadas partículas de prata (ilhas) revestidas na superfície de titânio para aplicação odontológica e ortopédica. O processo de revestimento das partículas de prata na superfície do titânio foi realizado por pulverização, que é uma técnica de deposição assistida por plasma e o titânio sem tratamento foi aplicado como padrão de comparação. Os parâmetros de tratamento com plasma foram otimizados para que o resultado não fosse um filme fino de Ag, mas partículas dispersas de Ag na superfície do Ti-cp. As superfícies das ligas foram investigadas por microscopia eletrônica de varredura (MEV) e espectroscopia de raios X dispersiva em energia (EDS). Para investigar o potencial antibacteriano Staphylococcus aureus e Escherichia coli foram utilizados no ensaio de difusão em ágar. Os resultados foram analisados por análise de variância (ANOVA), a fim de verificar diferenças significativas na atividade antimicrobiana entre amostras que não mostraram diferença entre as superfícies estudadas. Para partículas de prata dispersamente depositadas (ilhas) sobre a superfície de titânio para tratamento de 10 minutos, o EDS revelou, ao apresentar aglomerados de prata, que as partículas não foram adequadamente dispersas na superfície, logo a baixa efetividade na atividade antibacteriana.

This work shows microstructural evidences of morphological transformation from as-hardened martensite to C-expanded martensite as a result of the low-temperature plasma carburizing treatment carried out in AISI 420 martensitic stainless steel. Treatments were carried out at different treatment temperatures (350, 400, 450, and 500 °C, for a 12 h fixed time) and times (12, 24, 36, and 48 h, at 400 °C fixed temperature). Confocal laser scanning microscopy and SEM results show martensite coarsening in the treated surfaces regarding the respective substrate bulks, which is related to the surface C-alloying, thus being dependent on the treatment time and temperature. Hardness measurement and XRD results strongly suggest that the martensite coarsening is related to the transformation from lath- to plate-type martensite due to the enhancement of the martensite C content, in accordance with the Zener ordering theory. For samples carburized at relatively low temperatures (namely 350, and 400 °C), as C diffuses in paraequilibrium, strain-induced transformation mechanism would govern the changes in the initial martensite morphology as a result of its C content increase. On the other hand, as the chromium carbide precipitation occurs for samples treated at relatively high temperatures (higher than 450 °C for 12 h), and long times (longer than 36 h at 400 °C), C atoms would leave the supersaturated (expanded) martensite phase solid solution, leading the plate martensite to transform back to lath martensite.

The application of low-temperature plasma carburizing (C), nitriding (N) and nitrocarburizing (NC) treatments in sequential steps on AISI 420 martensitic stainless steel was investigated through nine different treatments. Experiments were performed at 400 °C, being divided in three (8 h)-single treatments, namely C, N and NC, and six distinct (4 h + 4 h)-sequential treatments, namely C + N, N + C, C + NC, N + NC, NC + N, and NC + C, using appropriate gas mixtures for each treatment step. Sequential treatments promoted the formation of treated layers constituted of iron carbides/nitrides, chromium nitrides, and nitrogen/carbon-expanded martensite phases. Interesting results were obtained for both C + N and C + NC sequential treatments, whose application results in greater hardening depths (~20% thicker) and leads to ~40% increase on the surface hardness, when compared to the obtained for the single C treatment keeping a smooth hardness profile. From the microstructural characterization, no significant sensitization was evidenced in the outer layers obtained for all treatments comprising the carburizing step, an indicative result that the interstitial carbon retards the chromium-rich particles precipitation kinetics. The combination of N + NC treatments produced thicker and harder treated cases compared to those produced by the respective single treatments. In brief, results showed that the appropriate selection of thermochemical treatments' sequence can promote increased treatments efficiency concerning the treated layers thickness or effective surface hardness. This work also contributes to the validation of the presented processing approach, proving its advantages over single thermochemical treatments.

RESUMO Corpos de prova de aço inoxidável austenítico ISO 5832-1(similar ao AISI 316L, para aplicações biomédicas) apresentando camada superficial enrriquecida em nitrogênio (fase S), obtidos pelos processos de nitretação por plasma em baixa temperatura e SHTPN (Solution Heat Treatment after Plasma Nitriding -Tratamento de solubilização após nitretação por plasma), além de amostras não tratadas, foram testadas em ensaio de desgaste microabrasivo do tipo esfera livre. Os resultados mostraram que as superfícies nitretadas por plasma em baixa temperatura apresentam o menor coeficiente de desgaste para menores tempos de ensaio. No entanto, devido à pequena espessura de camada nitretada, com o aumento do tempo de ensaio as amostras processadas via SHTPN passam a apresentar desempenho superior, indicando que, dependendo das solicitações de desgaste, um ou outro processo apresenta o melhor desempenho. ABSTRACT Samples of the ISO 5832-1 austenitic stainless steel (similar to AISI 316L for biomedical applications) with nitrogen-rich surface layer (S-phase), obtained by plasma nitriding at low temperature and SHTPN (Solution Heat Treatment after Plasma Nitriding) processes, as well as non-treated samples, were tested to evaluate its micro-abrasive wear behavior. The micro-abrasive wear test were performed using the free-ball configuration. The results pointed out that the nitrided surfaces present lower wear coeficient for short measuring time. Nevertheless, since nitrided layers are relatively thin, for prolongated wear tests the SHTPN samples presented lower wear cofiecient, indicating that depending on the apllication one of the processes will present the best behaviour.

The UNS S32750 super duplex stainless steel (SDSS) was low temperature plasma nitrided at 350 °C and 400 °C for 4 h. Pitting and crevice corrosion resistance was evaluated using electrochemical techniques in a NaCl neutral solution. Nitriding treatments resulted in increased in hardness, general corrosion resistance and in the passive layer breakdown potential. Regarding crevice corrosion tests, the nitrided surfaces showed lower current densities during the potentiostatic polarization and lower corrosion depths when compared to the untreated surface. The nitrogen played a fundamental role in the passivation behavior and in the susceptibility to repassivation of localized corrosion.

Surface engineering is unavoidable for most high-performance components manufacturing. Frequently when very specific properties are required duplex treatments are necessary. In the case of diffusion-based treatments, like nitriding and chromizing, the substrate composition plays an important role in the obtained results. Consequently, for duplex treatments, the second treatment will be influenced by the first one. Putting these aspects in evidence, Deutsches Institut fur Normung (DIN) CK15, DIN C45Pb, and DIN X40CrMoV5-1 steels were exposed to pack chromizing followed by plasma nitriding and plasma nitriding followed by pack chromizing. Results showed that the treated surface features are very sensitive to the steel composition and treatment sequence. In nitrided and chromized surfaces, the iron nitrides formed during the first treatment are dissolved and replaced by chromium nitrides (CrxNy) during chromizing. The inverse sequence resulted in surfaces containing chromium carbide (Cr7C3) formed during chromizing with CrxNy and iron nitrides formed during nitriding. The higher measured hardness (1,499 Vickers hardness [HV]) was obtained for the chromized and nitride DIN X40CrMoV5-1 steel. Salt spray tests showed that treatments ending by chromizing are the most promising for enhancing the surface corrosion resistance, except for the low carbon steel.

This paper reports on the dry sliding behavior (block-on-ring tests) of Low-Temperature Plasma Carburized (LTPC) AISI 420 martensitic stainless steel, treated under different times (4–16 h) and temperatures (350–500 °C), so as to identify the relationships between microstructure, micro-hardness and tribological behavior. In particular, LTPC was effective in decreasing wear when treatment conditions led to the highest diffusion layer thickness combined with absence of a thick outer layer (i.e. at 450 °C for a treatment time of 12 h). The dominant wear mechanism was mild tribo-oxidation, with the protective oxide tribolayer being partly removed by abrasive debris in samples treated at 500 °C.

The present work is aimed at advancing a computational model for predicting the thermal conductivity of frost formed under different working conditions and, therefore, spanning a wide range of frost morphologies. The frost growth was modeled by means of the fractal theory, particularly the diffusion-limited aggregation approach which forms heterogeneous porous media that emulate the morphology of the frost layer. The density of the frosted medium was determined straightforwardly by the principle of mass conservation, whereas the effective thermal conductivity was calculated from the inverse solution of the heat diffusion problem using the finite-volume method. It was found that the model predictions for the thermal conductivity were able to represent the experimental data obtained in-house within the ±15% thresholds. A sensitivity analysis of key operating conditions that affect the frost morphology is also reported.

This work shows in details how the γ→α′(e) (austenite (γ), martensite (α′, e)) strain-induced martensitic transformation affects the cavitation erosion behavior of the solution-treated AISI 304 austenitic stainless steel. For this purpose, mirror-polished surface samples initially presenting ~93 vol% γ + ~7 vol% α′ were subjected to cavitation erosion testing according to ASTM G32-10 , being carefully characterized by X-ray diffraction and hardness measurements at the tested surfaces. Under cavitation, the studied steel surface showed total γ→α′ transformation fraction of ~89 vol% (which supposedly is directly related to the needed ~4 vol% expansion for the transformation), with no effective mass loss for 180 min testing time, clearly defining the transition from the incubation period (IP) to the acceleration stage of the cavitation testing. For this transformation condition, initially presenting remaining ~11 vol% γ fraction, successive material removal steps and XRD analysis were carried out aiming at determining the actual depth at which this cavitation-related transformation takes place into the steel austenitic matrix. In this case, ~57 μm depth was found when XRD patterns before testing (leading to ~93 vol% γ results) were obtained. Finally, the variation of the average γ→α′ transformation rate along all IP presented a maximum level of ~0.60% min−1 between 60-120 min, which is attributed to the great difference on the mechanical properties of the γ and α′ phases, whose volume fractions continuously change at the surface under cavitation, thus affecting the evolution of the referred surface transformation.

As-hardened (fully martensitic) and as-tempered (with 14 ± 2% reversed austenite in a martensitic matrix) samples were subjected to cavitation testing in order to characterize the behavior of the reversed austenite and understand how it influences the CA-6NM steel cavitation behavior. Results showed similar nominal incubation periods of 3 h for both the studied conditions. For the first time, it is shown that the as-tempered CA-6NM steel incubation stage can be divided in two distinct parts: i) the IP I, period mainly related to γREV→α′ strain-induced transformation; and IP II, period mainly related to α′ deformation. It was concluded that the reversed austenite plays important role in the incubation stage of the CA-6NM steel, delaying the expected start of the cavitation erosion.

Formation of metastable C–, N–, or even Formation of metastable C–, N–, or even C/N– expanded phases can be observed for typical non-equilibrium conditions attained at the plasma assisted thermochemical treatments when temperatures relatively low are used. In present work, kinetics data are considered in a comparative study comprising low-temperature plasma assisted carburizing, nitriding and nitrocarburizing of AISI 420 martensitic stainless steel samples treated at 350, 400, and 450 °C, aiming to put in evidence the main metallurgical differences of the obtained layers. Microstructural characterization and hardness measurement results for untreated and treated sample surfaces show significant difference for the carburized layer growth in relation to that verified for the nitrided and nitrocarburized layers. While the carburized layer is constituted of a thin outer layer and a deep diffusion layer, just the opposite was observed for the other two treatments, id est., formation of thicker outer layers and thinner diffusion layers. Finally, carbide-/nitride-precipitation-free layers were supposedly obtained for samples carburized, nitrided, and nitrocarburized at 350 °C temperature.

Low-temperature plasma nitrocarburizing was performed in order to study the effect of treatment temperature and time on the microstructure, mechanical properties and growth kinetics of the AISI 420 martensitic stainless steel treated layers. Plasma nitrocarburizing was carried out using DC-pulsed power supply in a 71% N 2 + 18% H 2 + 10% Ar + 1% CH 4 gas mixture, at temperatures of 300, 350, 400 and 450 °C, and times of 2, 4, 6 and 12 h. The applied peak voltage, gas flow rate and pressure were kept constant at 600 V, 3.32 × 10 − 6 Nm 3 s − 1 and 400 Pa, respectively. The treated samples were characterized by optical microscopy, X-ray diffractometry and microhardness measurements. A maximum surface hardness of 1280 ± 16 HV 0.3 was obtained for samples treated for 4 h at 400 °C. Grain boundary chromium carbide/nitride precipitation has started for treatments of 4 h at 400 °C, which can be avoided by using lower nitrocarburizing temperature or time. It was verified that nitride/carbide precipitation tends to occur at lower temperatures and times when compared with the low-temperature nitriding and carburizing treatments. Finally, the nitrocarburized layer growth is proportional to the square root of treatment time and follows an Arrhenius law for the treatment temperature, with an activation energy of 76 kJ mol − 1 .

The present paper is aimed at putting forward a two-dimensional model for thermoelectric cells. The energy conservation equation was formulated in order to account for the Fourier (heat) conduction, the Thomson (thermoelectric) effect, and the Joule heating on the temperature distribution. The electric field was also modelled in order to come out with the current and voltage distributions. The governing equations were discretized by means of the finite-volume method, whereas the TDMA algorithm was adopted for solving the sets of linear equations. An explicit solution scheme was employed to address the temperature influence on the thermoelectric effect. The model results have been compared with experimental data, when a satisfactory agreement was achieved for both cooling capacity and COP, with errors within a 10% band. In addition, the model was employed to assess the effects of the thermophysical properties and the couple geometry on the thermodynamic performance of the thermoelectric cell.

This work reports experimental results on sintered PIM 316L stainless steel low-temperature plasma nitriding. The effect of treatment temperature and time on process kinetics, microstructure and surface characteristics of the nitrided samples were investigated. Nitriding was carried out at temperatures of 350, 380, 410 and 440 oC , and times of 4, 8 and 16 h, using a gas mixture composed by 60% N2 + 20% H2 + 20% Ar, at a gas flow rate of 5.00 × 10-6 Nm3s-1, and a pressure of 800 Pa. The treated samples were characterized by scanning electron microscopy, X-ray diffractometry and microhardness measurements. Results indicate that low-temperature plasma nitriding is a diffusion controlled process. The calculated activation energy for nitrided layer growth was 111.4 kJmol-1. Apparently precipitation-free layers were produced in this study. It was also observed that the higher the treatment temperature and time the higher is the obtained surface hardness. Hardness up to 1343 HV0.025 was verified for samples nitrided at 440 oC. Finally, the characterization of the treated surface indicates the formation of cracks, which were observed in regions adjacent to the original pores after the treatment.

The present paper reports the experimental results on martensitic stainless steel low-temperature plasma assisted carburizing kinetics. The treatments were carried out using a gas mixture of 99.5% (80% H2 + 20% Ar) + 0.5% CH4 at temperatures of 623, 673, 723 and 773 K and for times of 4, 8, 12 and 16 h. The peak voltage and the pulse period of the pulsed DC power supply were kept constant at 700 V and 240 μs, respectively. Temperature was controlled by adjusting the duty cycle. The treated samples were characterized by confocal laser scanning microscopy, X-ray diffractometry and microhardness measurements. Results indicate that low-temperature plasma carburizing is a diffusion controlled process. The calculated activation energy for outer and diffusion layer growth was 29 and 85 kJ mol− 1, respectively. An apparently precipitation-free layer can be produced only when the processing temperature is sufficiently low (≤ 723 K) and time sufficiently short (≤ 12 h).

DC plasma is a very promising technology for processing different materials, and is becoming especially interesting when low environmental impact and high-performance treatments are needed. Some of the intrinsic characteristics of DC plasma technology, which make it suitable for powder metallurgy (PM) and powder injection molding (PIM) parts production, are low-pressure processing and plasma environment high reactivity. Moreover it can be considered as a highly competitive green technology. In this work, an overview of some of the important DC plasma techniques applied to PM and PIM parts processing is presented. Emphasis is given to the descriptions of the main characteristics and the technique potentials of plasma-assisted nitriding, plasma-assisted thermal debinding, plasma-assisted sintering, and simultaneously plasma-assisted sintering and surface alloying. The aspects presented and discussed in this paper indicate that DC plasma processes are promising and competitive techniques for PM and PIM parts processing.

Plasma technology used to perform thermochemical treatments is well established for the majority of steels, but it is not the case for the different stainless steel classes. Thus, im‐ portant scientific and technological achievements can be expected in the coming years re‐ garding plasma-assisted thermochemical treatment of such steels. The metallurgical aspects as well as the application cost-efficiency of stainless steels impose specific re‐ quirements for the thermochemical treatment, such as easy native chromium-rich oxide layer removal and surface activation at low temperature, which do not appear for other steel classes (plain, low-alloy, and tool steels). Thus, due to the highly reactive physico‐ chemical environment created by the plasma, plasma-assisted technology presents ad‐ vantages over other “conventional” technologies like those performed in gas or liquid environments. Low temperature is needed to avoid the reduction of corrosion resistance of stainless steels, by suppressing chromium carbide/nitride precipitation, and, in this case, good surface properties are achieved by the formation of treated layers containing metastable phases. Such attributes make the low-temperature plasma thermochemical treatments of stainless steels an important R&D field in the domain of plasma technology and surface treatments, and the goal of this chapter is to introduce the reader to this im‐ portant topic.