The Impact of Heat Treatment on the Behavior of a Hot-Dip Zinc Coating Applied to Steel During Dry Friction

Abstract

The analyzed topic refers to the wear resistance and friction coefficient changes resulting from heat treatment (HT) of a hot-dip zinc coating deposited on steel. The aim of research was to evaluate the coating behavior during dry friction after HT as a result of microstructure changes and increase the coating hardness. The HT parameters should be determined by taking into consideration, on the one hand, coating wear resistance and, on the other hand, its anticorrosion properties. A hot-dip zinc coating was deposited in industrial conditions (according EN ISO 10684) on disc-shaped samples and the chosen bolts. The achieved results were assessed on the basis of tribological tests (T11 pin-on-disc tester, Schatz®Analyse device, Sindelfingen, Germany), microscopic observations (with the use of optical and scanning microscopy), EDS (point and linear) analysis, and microhardness measurements. It is proved that properly applied HT of a hot-dip zinc coating results in changes in the coating’s microstructure, hardness, friction coefficient, and wear resistance.

The Influence of Heat Treatment on Corrosion Resistance and Microhardness of Hot-Dip Zinc Coating Deposited on Steel Bolts

“…On the other hand, heat treatment can also lead to the appearance of microcracks visible in the cross-section of the coating (reducing the compactness). The obtained results are similar to those achieved in the previous tests with application of disk samples [ 47 ]. This also proves that the conducted analysis of heating kinetics was correct, and the heat treatment parameters selected on its basis made it possible to obtain comparable results on both flat samples and M12x60 bolts.…”

“…To solve the above task, the concept of target programming was used, according to which the original two-criteria task is replaced by a single-criteria task, in which the cumulative criterion is the distance from the ideal point in the criteria space in the sense of the square of the Euclid metric [ 62 ]. The following values were accepted as the coordinates of the ideal point: = 140 HV i = 324 h. In the first step, in the space of decision variables, a set of acceptable solutions was defined, which is determined by the permissible intervals of variation of heat treatment parameters (t = 270–430 °C, = 7–11 min) fixed on the basis of the analysis of the results of preliminary tests [ 47 ]. The permissible set took the shape of a rectangle shown in Figure 7 .…”

“…The bolts were held at the treatment temperature in time τ = 7–11 min. The parameters of heat treatment were selected based on the preliminary tests performed at work [ 47 ] with the use of disc-shaped samples measuring 25 mm in diameter and 4 mm in thickness and compared with the kinetics of heating disc samples and bolts (M12x60) using a thermal imaging camera. Table 1 presents values of the heat treatment parameters applied in the tests together with the variant numbers (1–9), i.e., the trivalent fractional plan (three values of variable parameters) for two input quantities (temperature and time of heat treatment).…”

“…Considering the data from the literature and results of our own research presented in the previous article [ 47 ], where both disk samples and bolts were tested and the effect of heat treatment on the change of zinc coating microhardness, microstructure and coefficient of friction was studied, it seems crucial to assess the impact of the proposed heat treatment on the change in corrosion resistance of the tested coatings.…”

The Comparative Analysis of the Coatings Deposited on the Automotive Parts by the Cataphoresis Method

“…Taking into account the above literature analysis, a similar cost of zinc and KTL coatings (depending on the time of protection and the size of the protected element [ 44 , 45 ]) and similar corrosion resistance of the compared coatings [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ], in this paper, the research on the impact of the base (steel) surface preparation on the properties of KTL coating was investigated. The results obtained were compared to those presented in the authors’ earlier studies on zinc coatings [ 46 , 47 , 48 ].…”