The Influence of Salt Bath Nitriding Variables on Hardness Layer of Aisi 1045 Steel

Abstract

The aim of this paper is to study and analyze the effects of a surface controlled salt bath nitriding on the microhardness of AISI 1045 steel. The nitriding process was implemented in the salt bath component at ten different times (from 1 h to 10 h) when the temperature was constant at (520ºC). The nitriding process repeated of other specimens at the same times, but the temperature was (580ºC).The microstructure of the surface layers was investigated by scanning electron microscopy (SEM) and optical microscopy. Hardness profiles were measured with lowload hardness testing to determine the growth of the case depth after nitriding. Microhardness testing was carried out on samples to investigate the hardness profile at the transition from the compound to the diffusion layer. The microhardness of the surface of the nitrided sample at 520ºC and 580ºC was observed in the range of 318-430 HV0.3 and 329-421 HV0.3, respectively. Experimental results showed that the nitrides ε-Fe2-3(N, C) and γ'-Fe4(N,C) present in the compound layer increase the microhardness , It also showed that the Increasing the salt bath nitriding parameters (treatment time and temperature) increases the surface hardness and hardness profile.

Nitriding in low carbon steels using non-toxic salt baths

“…This aspect complicates the nitriding process, because the carbon spreads toward the steel core and a carbon-rich layer accumulates before the nitride reaction front. As far as we know, until this present day, any nitriding process for steel without simultaneous carbonatation was performed with salt baths (GHELLOUDJ et al, 2016;SHEN;OH;LEE, 2005).…”

“…Some of these methods are superficial treatments, which are considered the best methods to prevent corrosion, friction and wear (CAI et al, 2012;PENG, 1989;PODGORNIK et al, 2001). For these superficial treatments, there are three basic requirements for coatings: good adhesion, chemical stability as well as high structural and phase stability (GHELLOUDJ et al, 2016;THIELE;LEHNERT, 2017).…”

Effect of Time on the Compound Layer Formed During Salt Bath Nitriding of Aisi 4140 Steel

“…During the process, a two parts surface layer is formed, an outer compound layer (ε + γ') with a nitrogen diffusion layer (α) below it [22]. It is called Compound layer also 'white layer' [23,24,25], it inferred that the hardness and the depth depend largely upon the time and the temperature of the salt bath nitriding treatment. [22], initial microscopic situation of the steel [26,27], the amount presence of nitride elements in the steel [26,28].…”

Effect of Salt Bath Nitriding on Surface Roughness Behaviour of Aisi 4140 Steel

“…Salt bath nitriding [3,4,5] is one of the most widely used thermo-chemical methods [6,7,8], which produces strong and shallow case with high compressive residual stresses on the surface of steel components such as gears, crankshafts, dies and tools [9,10,11]. Surface roughness of industrial components strongly affects their performance, i.e, many surface properties such as friction [12][13], surface wear [14], fluid flow in rough pipes [15] and the functioning of vacuum seals [16] are strictly dependent on surface roughness.…”

“…There are at least five different mechanisms by using the surface modification methods to increase the fretting resistance: (1) to induce a residual compressive stress; (2) to decrease the coefficient of friction; (3) to increase the surface hardness; (4) to alter the surface chemistry; (5) to increase the surface roughness [19]. DOI There's plenty of research that aims to predict the behaviour of steel after nitriding treatments, AISI 5140 [20][21][22][23][24][25], AISI 430 [21], AISI 1045 [22], AISI 4340 [23], AISI 410 [24], API X-65 [26], Fe-Cr alloys [27] and examine changes in the resulting structures of treatment nitrided components by plasma nitriding [28,29,32,33], ion nitriding [30,31,34], plasma nitrocarburizing [35] and salt bath nitriding [5]. On the other hand there's many studies interested to study surface roughness [36,37,38,39,40,41], methods of measurement of surface roughness parameters [43,44,45,47] and others [42,46,48].…”