Tribological properties of boride based thermal diffusion coatings

Abstract

Engineering components, e.g. tubing systems for the down-hole applications in the oil and gas industry (in particular, sucker rod pumps, progressing cavity pumps and some other components of the artificial lifting systems), as well as numerous valves and seats, bearings, gears and plungers, require protection against friction and sliding abrasion service conditions. The hard boride based coatings on steels and alloys obtained through the thermal diffusion process have a high potential for these severe application conditions over many other types of coatings as they can be obtained on the entire working surfaces of large size and complex shape products. Intensive tribological studies of the iron boride based coatings on carbon steel obtained at Endurance Technologies Inc. have been conducted using the Cameron-Plint testing unit (reciprocating sliding of the metallic rod under the load over a flat surface of the coated samples). The friction wear loss, friction coefficient and structural changes of the coatings have been studied in dry and lubricating (water-oil) friction conditions, which simulate actual application conditions. It was demonstrated that the obtained boride coatings have the friction loss significantly smaller than untreated steel (e.g. y10-30 times in the dry conditions and at least 5 times in the lubricating conditions) with no peeling and flaking-off. The friction coefficients of the boride coatings are steady over the test duration. The influence of the thickness on the boride coatings performance is demonstrated. The encouraging results are explained by the specific coating structure of the hard coating obtained through the thermal diffusion process and the thin 'tribofilm' formed during a friction mode.

Formation of Corrosion‐Resistant Thermal Diffusion Boride Coatings

“…In the case of small case depth (below 75 μm), the forming iron boride phases are not well consolidated yet with the presence of some residual porosity and surface flaws that reduces the corrosion resistance of the coatings. In addition, the components with the case depth of 150–200 μm are the most reasonable for the wear‐protection applications, e.g., for abrasion and friction conditions, and many industrial applications include various combinations of wear and corrosion situations. Another situation occurs with boronizing of stainless steels.…”

“…The boronizing process even promotes surface smoothness; practically, the level of surface roughness ( R grade number) is reduced by one grade or more for the boronized steel versus untreated carbon steel. Thus, surface roughness of the boronized carbon steels with case depths of 100–250 μm is in the range of 2.5–3.5 μm ( R grade number 7–8), while bare carbon steels have surface roughness of 7–8 μm ( R grade number 9–10), i.e., smoother surface formation through boronizing may be considered as an additional positive feature improving corrosion resistance.…”

Microstructure and Abrasive Wear Resistance of Metal Matrix Composite Coatings Deposited on Steel Grade AISI 4715 by Powder Plasma Transferred Arc Welding Part 1. Mechanical and Structural Properties of a Cobalt-Based Alloy Surface Layer Reinforced with Particles of Titanium Carbide and Synthetic Metal–Diamond Composite

“…The making of layers characterised by new and unique properties may entirely change the operational parameters of every base material. Related publications concerning the subject discuss the obtainment of the increased abrasive wear resistance of tools primarily through the application of ceramic materials [ 11 , 12 , 13 ], diffusive carbide [ 14 , 15 , 16 ], boride coatings [ 17 , 18 , 19 ] and thermally sprayed layers [ 20 , 21 , 22 ]. Some of the above-named methods fail to produce desirable results and, in addition, are both energy-consuming and laborious.…”

“…However, stellites are less frequently referred to as matrix materials in composite layers and more often as homogenous layers. Particles reinforcing composite surface layers are various interstitial compounds, usually carbides but also nitrides and borides [ 15 , 17 ]. The most commonly used carbides include tungsten carbide (WC) [ 30 , 38 ], silicon carbide (SiC), boron carbide (B 4 C) [ 39 ] and titanium carbide (TiC) [ 40 ].…”

Evolution of the Microstructure and Properties of Pre-Boronized Coatings During Pack-Cementation Chromizing

“…Therefore, the B-Cr coating has great application prospects in the field of surface protection of metal materials. Pack-cementation is a frequently-used method to prepare thermodiffusion coatings [26][27][28][29][30][31][32][33] and metallurgical bonding can be produced between the coatings and the substrate materials by this method [34]. For the B-Cr duplex coatings prepared by pack-cementation, depending on different treatment orders, three kinds of processes can be chosen: simultaneous boronizing and chromizing (SBCr), chromizing followed by boronizing (CrB), and boronizing followed by chromizing (BCr) [24,25,35].…”