High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions

Abstract

Press hardening is widely employed to produce automotive structural and safety components from advanced high-strength steels. This process depends on friction between the forming tools and the work piece. Wear of the forming tools affects the dimensional accuracy of produced components and reduces their service life. It is therefore desirable to reduce wear of forming tools for press hardening applications. One way to achieve this is by applying hard physical vapour deposited (PVD) coatings on the tool. In this work, the tribological behaviour of PVD coated tool-work piece material pairs has been studied at elevated temperatures in an experimental set-up simulating the tribological conditions in press hardening. Four different PVD coatings deposited on tool steel and uncoated tools as reference were studied during sliding against uncoated and Al-Si coated 22MnB5 steel. Results show that uncoated tools exhibited the lowest coefficient of friction when sliding against uncoated 22MnB5 steel. A CrWN coating initially showed low coefficient of friction but it increased with increasing sliding distance. A TiAlN coating and one of two AlCrN coatings showed similar frictional behaviour when sliding against uncoated 22MnB5 steel. During sliding against uncoated 22MnB5 steel, adhesive wear has been found to be the dominant wear mechanism. Adhesive wear was considerably reduced in the case of hard PVD coated tools in comparison to that of uncoated tools. During sliding against Al-Si coated 22MnB5 steel, no clear advantage in terms of friction behaviour of uncoated or PVD coated tools was observed. However, the transfer of Al-Si coating material from the work piece to the tools was significantly reduced for PVD coated tools. Frictional instabilities in all cases involving Al-Si coated work piece material further confirmed the occurrence of adhesive material transfer.

Friction and wear mechanisms during hot stamping of AlSi coated press hardening steel

“…The coefficient of friction found in this study is in agreement with previous studies, 0.42-0.67 [6], $ 0.56 [29], 0.4-0.5 [5], 0.5-1.2 [10], 0.5-1.8 [21], 0.48-0.59 [16], 0.42-0.46 [4], 0.38-0.78 [30], 0.37-0.4 [7], 0.40-0.45 [17], $ 0.55 [20], 0.52-0.58 [31] and $ 0.56 [22]. However, the reported values are mean coefficients of friction and do not provide a detailed physical understanding that leads to the undesired friction and the tremendous tool wear in hot stamping processes.…”

“…Industrial tools for AlSi coated blanks are investigated by Pujante [8,9], Pelcastre [10] and Vilaseca [4] and the main wear mechanisms are paired with material transfer. Material transfer of the sheet coating to the tool is also observed at the laboratory set ups such as high temperature pin on disc test [3,5,[10][11][12][13][14][15][16], strip drawing over radius [17,18], cup deep drawing [19], and hot strip draw tests [7,[20][21][22]. Several authors make a distinction between build up of 'normal load' adhesion, accumulation and compaction of dust/coating wear debris [3,4,8,23].…”

“…So far, the investigations on the characterization of friction phenomenon during hot stamping processes is mainly limited to measuring mean (global) coefficients of friction [4][5][6][7]10,17,[20][21][22]29,30]. However, it has been shown that contact condition and/ or friction between tool and blank is local and could not be described or modeled using a constant friction coefficient in finite element analyses [26][27].…”

Properties of Diamond-like Tungsten-Doped Carbon Coatings Lubricated with Cutting Fluid

“…Their important functional characteristics are high hardness, wear resistance, and chemical inertness. These properties are inherent in diamond-like carbon (DLC) coatings consisting of bonds such as sp3, characteristic of diamond; sp2, characteristic of graphite; and sp1 with α and β carbine structures [15][16][17]. Due to their low friction coefficient, corrosion resistance and biocompatibility, DLC coatings are used in medicine for hip, knee, or shoulder implants, blood pumps, heart valves, or artificial heart components [18][19][20][21][22].…”

The wear of PVD coated elements in oscillation motion at high temperature

“…The benefits of composite substrate usage can be optimized by the deposition of a PVD coating as an additional protection. However, to conduct it in an effective way, it is vital to consider their potential field of implementation at the design stage [3,4]. Currently, there is no universal composition and structure of coating that can be effective in a wide range of temperatures [5,6].…”