Combined Use of Surface Texturing, Plasma Nitriding and DLC Coating on Tool Steel

Abstract

In cold rolling, a textured roll can be used to imprint a desired surface topography onto the sheet during rolling. This work proposes the use of diamond-like carbon (DLC) coatings to protect the surface topography of the rolls in replacement of the carcinogenic hard chrome. For that, hydrogenated amorphous carbon (a-C:H) was deposited on plasma nitrided tool steel, both for ground and textured specimens. Changes in surface topography due to DLC coating were assessed using a confocal microscope. Coating adhesion was evaluated using the method VDI 3198. The specimens were characterized using X-ray diffraction (XRD), microhardness test and scanning electron microscopy (SEM). The coating was characterized using Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS). The results showed a soft multilayer coating consisting of a plasma nitrided layer for load support, a Si-rich interlayer to improve adhesion and an a-C:H top layer. DLC deposition reduced the roughness of the textured specimens. The coating resulted in relatively stable friction and good durability, with small damage and negligible wear even under dry sliding.

Brazilian Tribology: origin, status quo and future perspectives

“…More recently, the influence of surface texturing and hard chromium coating on the wear of steels used in cold rolling mill rolls [110] was undertaken. Those studies led to the need to develop a methodological approach [111] which served as the basis for the study of alternative surface modifications for cold rolling mill rolls [112] as well as the combined use of surface texturing, plasma nitriding and DLC [113]. The analysis of the process of generating wear particles during the cold rolling of stainless steel was the subject of a complete study in partnership with the Brazilian industry [114].…”

“…Activities related to tribology and surface engineering at the Federal University of Rio Grande -FURG started in 2016 when Prof. Henara Costa moved from LTM/ UFU to FURG, culminating with the creation of the Laboratory of Surface Engineering (LabSurf) in 2019. The works span from surface engineering techniques such as surface modifications [113,280,[320][321][322][323][324][325][326][327][328][329][330][331][332] and different coating technologies [112,113,[333][334][335] to their effects on surface topography [102,103,121,326,[336][337][338], surface hardness [339][340][341], machinability [2], formability [337,342,343], corrosion [335,[344][345][346], tribological performance [13, 50-52, 113,280,320,322,333,337,347,348] and tribo...…”

“…The equipment has allowed investigations to understand the interaction between different substrates (tool material types and processing) and engineered surfaces such as PVD coatings and the formation of tribo-layers, evolution of friction and wear mechanisms [337]. Furthermore, collaborations with LTM/UFU, LabMat/UFSC and UDESC have enabled the investigation of the combined use of surface texturing and coatings to improve the tribological performance of cold rolling mill rolls [110][111][112][113].…”

Tribological and Mechanical laboratory Analysis of DLC as substitutes for hard chromium coating in view of Cold Rolling of High Carbon Steel Strips

“…Kalin et al have reviewed how these properties interfere with the mechanisms involved in boundary lubrication [14], an important feature for the tribology of rolling processes. Dos Santos de Almeida et al [19] were interested in DLC coating in nishing cold rolling. They carried out ball-on-at tests with the ats being cut from rolling mill roll steel and coated with hydrogenated DLC.…”

Improved Adhesion of the DLC Coating Using HiPIMS with Positive Pulses and Plasma Immersion Pretreatment

“…Nitriding treatments have been shown in other studies to improve the adhesion properties of deposited coatings such as PVD, CVD or DLC [20][21][22][23]. However, for austenitic stainless steel, this type of solution is not applicable since the stainlessness is lost due to the precipitation of chromium nitrides at high temperatures.…”