Nitriding

There are two basic options for improvement of surfaces of heat treated tool steels for cold working: mechanical treatment such as burnishing, or else chemical modification such as nitriding. The latter is affected not only by the nature of the chemical agent but also by diffusivity of that agent through the steel. We focus first on the number and order of operations performed on the steel surfaces: turn-edþ burnished (T þB), turned þnitrided (TþB) and turned þburnished þnitrided (T þB þN). We have investigated two tool steels, Sverker 21 (AISI D2) and Vanadis 6. The former belongs to traditional steels, the latter is classified as advanced powder metallurgy (P/M) alloyed steel. We have performed pin-on-disc tribological experiments to determine abrasive friction and wear. Our evaluation of tribological properties of these two cold working steels enables an improvement of their manufacturing procedures leading to significant wear reduction. The improvement proposed is applicable not only to tool steels but also for instance to titanium alloys.

The focus of this research is to show how high sustainability rates can be achieved through lightweighting in the cost-effective way and to demonstrate what type of benefits mass reduction provides. The main goal of this research is to fill a gap in the literature about automotive sector and to reveal some functional solutions for the automotive giants through performing tests for obtaining meaningful data. In this study, researcher wanted to combine environmental, economic and social aspects for generating high qualified component for Dennis Eagle - one of the major automotive manufacturing companies across the United Kingdom - through reviewing the literature for finding effective solution to increase the lifespan of this component against abrasion.
This paper attempts to show how the wear resistance of the rear loading segment of the refuse collection trucks of Dennis Eagle can be increased and how this contribute to the sustainability and profitability of the company. The abrasion and fretting resistance of the component was improved through applying some surface modification techniques – heat treatments and coatings – After examination of the needs and requirements of the relevant part of the rear loading segment of refuse collection trucks of Dennis Eagle, carbonitriding, ferritic nitrocarburizing (Nitrotec), gas nitriding and WC – Ni thermal spray coatings were applied on the surface of this part. Their morphology and characteristics were identified through examining the microstructure and hardnesses and compared with the existing properties of this part. The findings of this research explore some illustrations about that WC – Ni thermal spray coatings and carbonitriding processes gave the effective results about improving the wear resistance of the structure through increasing the hardness of the surface and this has high influence on improving the lifespan of the relevant component. In this study, researcher provided how beneficial these purposed heat treatments and coatings are and what type of benefits they provide in the context of cost-effectiveness and sustainability through reducing the thickness of the existing steel of this segment.
After performing experimental procedure, some recommendations have been set for further research work in this dissertation through identification of limitations of this study. A natural progression of this work is to provide a new perspective on how the sustainability can be achieved through elimination of the wear related problems and to purpose a roadmap for the further studies about the lightweighting concepts for designing a satisfactory and commercially successful automotive product. These purposed steps can be found as suggested future work and recommendations in this dissertation. Although this research contains some limitations, this study provides effective and remarkable perspective about increasing the sustainability in the cost-effective way.

In the present study, the effect of surface mechanical attrition treatment (SMAT) on corrosion resistance and plasma nitriding behavior of AISI 304L stainless steel (SS) was investigated. Mechanical twins and deformation induced martensite phase were observed in the SMAT affected region. SMAT improved the corrosion resistance and nitriding kinetics of AISI 304L SS. Effective nitriding time and hence, the thickness of the nitrided layer were increased with increase in the duration of chemical etching and a decrease in the stability of passive layer on the SMATed specimens. Surface hardness of the nitrided specimens was dependent on the formation of expanded austenite (γ N) and its decomposition (especially, at higher effective nitriding time).

D2 belongs to traditional steels, frequently used in metalworking industry. Shot peening and nitriding are known to improve the wear resistance of D2. In this work we focus on processes of slide burnishing and industrial low temperature gas nitriding. The D2 steel specimens were first subjected to heat treatments (HT) prescribed by the manufacturer, turning (T), then burnishing (B) and nitriding (N). The reason for turning was achieving appropriate surface roughness. Deformation induced in slide burnishing can be better controlled then in shot peening because of deterministic nature of this process. Four different paths to prepare surfaces were employed: HT + T, HT + T + B, HT + T + N, HT + T + B + N. D2 steel is very sensitive to the final finishing, wear rates vary up to 300 %. Two of our procedures (HT + T + N and HT + T + B + N) are much superior to the others. Moreover, in the HT + T + N case, apparently the surface fatigue scaling off takes place.

In the present study, surface mechanical attrition treatment (SMAT) and plasma nitriding were conducted on AISI 2205 steel. SMAT was effective in enhancing the surface hardness of the steel by about 80%. The influence of SMAT on the corrosion behaviour of the steel was studied in a 3.5 wt-% NaCl solution. Due to the stable and thicker passive layer, improved corrosion resistance was observed for the SMATed steel. However, nitrogen diffusion during plasma nitriding was impeded by the improved passivation, especially for the lower duration (30 min) of chemical etching/cleaning (i.e. sputter cleaning in hydrogen plasma) of the specimen's surface. Furthermore, high chemical etching duration (120 min) resulted in improved surface hardness and nitriding kinetics.