Abstract: An internal combustion engine includes: a cylinder including a thrust region and an anti-thrust region; and a plurality of concave portions formed in a belt-like central region including a central portion in the axial direction of the cylinder and extending along the circumferential direction on an inner wall surface. In the central region, the number of concave portions formed in a first partial region having a first predetermined width along the circumferential direction of the thrust region and the number of concave portions formed in a second partial region having a second predetermined width that is smaller than the first predetermined width along the circumferential direction of the anti-thrust region is smaller than the number of concave portions formed in other regions of the central region.

Abstract: The present invention is directed to improved designs and methods for improving engine fuel efficiency by providing two-stage engine variable compression in running engines using connecting rod force reversals to rotate eccentric bushings to change the connecting rod length. Compression ratio changes are initiated by shifting a block-mounted cam such that it engages and flips a bi-stable toggle on the connecting rod. The clutch mechanism latches the eccentric at the eccentric rotation end point, whereupon the connecting rod acts as a rigid rod. The invention includes novel configurations of the lubricated journal bearing between the connecting rod and the eccentric that modify the squeeze film bearing effects and resulting friction. These configurations reduce the peak eccentric torque carried by the clutch mechanism while facilitating eccentric rotation at lower torque.

Abstract: A method of producing a piston includes a step of producing a naked piston having the skirt portion; a step of forming the skirt portion with streaks; a step of applying a skirt portion of the naked piston with a first film forming paint which is provided for producing the inner solid lubricant film; a step of heating the first film forming paint on the skirt portion at a temperature of 60° C. to 160° C. for a time less than 800 seconds to dry the same; a step of applying an outer surface of the dried first film forming paint with a second film forming paint which is provided for producing the outer solid lubricant film; and a step of heating the first and second film forming paints on the skirt portion at a temperature of 160° C. to 240° C. for a time of 15 minutes to 180 minutes.

Abstract: A piston assembly is disclosed which includes a crown and a skirt. The crown and skirt may cooperate to form a cooling gallery. The crown may include an axial support extending away from the combustion bowl, and radially inner and outer support surfaces that are abutted against corresponding radially inner and outer support surfaces of the skirt. The axial support may have a first diameter and a second diameter larger than the first diameter. The skirt may define an aperture receiving the first diameter of the axial support such that the second diameter of the axial support is supported in the skirt on a side of the aperture opposite the crown. The corresponding radially inner and outer support surfaces of the crown and skirt may each be abutted with a radially inner preload, and a radially outer preload, respectively.

Abstract: An assembly is disclosed for sealing the sliding interface between two objects capable of sliding or moving with respect to one another, but where the sliding interface must provide a substantial seal against pressure loss therethrough, such as where an assembly seals the sliding interface between a piston and a cylinder or between a rod and a bushing. The sliding interface includes a seal located in a seal groove, wherein the seal ring height is less than the height of the seal groove and the inner diameter of the seal is greater than the base of the groove. In one aspect, the difference in height is set by a shim and a piece of material of the same height as that of the seal ring.

Abstract: The invention relates to a sliding element, which comprises a support and a coating applied by means of thermal spraying on the support, wherein the coating comprises at least two phases and at least one of the at least two phases is recessed in respect of the other phase of phases.

Abstract: A multilayer lubrication coating film is formed on the outer surface of an object to be coated. The multilayer lubrication coating film comprises a lower-layer coating film formed on an outer surface of the object to be coated, and an upper-layer coating film formed on a surface of the lower-layer coating film. The lower-layer coating film has a higher Vickers hardness than the Vickers hardness of the object to be coated.

Abstract: A piston for an internal combustion engine has a piston head and a piston skirt delimited by a lower skirt edge. The piston skirt has a working surface assigned to its major thrust side (DS) and a working surface assigned to its minor thrust side (GDS), and a zone is assigned to each of the two working surfaces, which zone proceeds from the lower skirt edge and is exposed to a maximal stress during operation of the internal combustion engine. The zone of the working surface assigned to the major thrust side (DS) and/or the zone of the working surface assigned to the minor thrust (GDS) side is provided with a coating that has grooves that run vertically.

Abstract: A gas lubrication structure is provided with a high-temperature-side cylinder, an expansion piston lubricated relative to the high-temperature-side cylinder by gas, and a layer provided to the outer peripheral surface of the expansion piston and composed of a material flexible and having a higher linear expansion coefficient than the base material of the expansion piston. The thickness of the layer under normal temperatures is not less than the size of the clearance formed between the layer and the high-temperature-side cylinder. Also, even if the layer is thermally expanded under use conditions, the layer under normal temperatures has a thickness enabling a clearance to be formed between the layer and the high-temperature-side cylinder.

Abstract: A movable wall member, in form of an exhaust valve spindle (1) or a piston (7) for an internal combustion engine, comprises a base portion (17, 20) of an alloyed steel having a carbon-content in the range from 0.15 to 0.35% by weight, and an outer portion (14, 5) forming the surface of the wall member facing a combustion chamber. The outer portion is of a hot-corrosion-resistant alloy, which is nickel-based, chromium-based or cobalt-based. At least one buffer layer (18, 21) of an alloy is located in between the base portion and the outer portion. The alloy of the buffer layer is different from the alloyed steel of the base portion and different from the hot-corrosion-resistant alloy of the outer portion. The alloy of the buffer layer comprises from 0% to at the most 0.09% C in percent by weight of the buffer layer, and that the buffer layer has a thickness of at least 1.5 mm.

Abstract: A piston for an internal combustion engine includes a piston base material including a pair of skirt portions opposed to each other in a radial direction of the piston base material. The piston includes a multiple-layer coating formed on at least one of surfaces of the pair of skirt portions. The piston further includes marks provided to respective layers of the multiple-layer coating at locations different from each other.

Abstract: The invention relates to a two-part piston (1) for an internal combustion engine, consisting of an upper part (2) and a lower part (3) which is screwed to the upper part. The upper part (2) and the lower part (3) are in contact with each other, partially by means of inner bearing surfaces (25, 26) defining the lower side of an upper ring rib (10) and the upper side of a lower ring rib (11), and partially by means of outer bearing surfaces (28, 29) defining the lower side of the ring wall (9) and the upper side of a collar (27) applied to the lower part (29). In order to avoid frictional rubbing, frictional heat sealing and pressure-related material heat sealing, at least one of the bearing surfaces (25, 26, 28, 29) is easily and economically provided with a chrome layer (30) which has a structured surface comprising a plurality of raised parts and recesses.

Abstract: A piston allowing a lubrication layer of a resin coating with a low friction coefficient to be tightly adhered to a skirt portion of a piston for an internal combustion engine, with low friction, superior wear resistance, and superior anti-seizing properties and that can reduce wear of a cylinder inner wall even if the lubrication layer is peeled off or abraded, is provided. Metal or ceramic fine particles having an average particle diameter of 20 ?m to 400 ?m are injected with compressed air or compressed nitrogen as a mixture fluid onto the skirt portion of the piston, made of an aluminum alloy and produced by a method such as casting or forging, at an injection speed of 80 m/s or more or an injection pressure of 0.2 MPa or more to be collided with the skirt portion, thereby uniformly making a microstructure of a piston base material fine-grained in a depth range of 1 ?m to 15 ?m from a surface of the skirt portion and forming a modified layer with an activated surface.

Abstract: A piston assembly including a piston body having a crown and a skirt, the skirt including at least a major thrust face and a minor thrust face, wherein the piston body defines a bore between the major thrust face and the minor thrust face, and a wear coating applied to the major thrust face and the minor thrust face, the wear coating having a cured thickness of at least about 30 microns.

Abstract: A process for hardening an annular groove of a piston head of a piston of an internal combustion engine by means of laser beams, in which, at least the annular groove to be hardened is provided before or directly during the hardening process with a coating which absorbs the energy of laser beams. The coating is subsequently irradiated by the laser beams. The absorbing layer can be a manganese phosphate coating or is formed in situ by treating the component surface with a process gas comprising oxygen and inert gas. Furthermore, the laser beams are directed at the piston during hardening at an oblique angle to the direction of rotation. The advantages achieved are avoidance of reflections and undesirable hardening of the bottom of the groove, an increased degree of absorption and reduced distortion of the piston.

Abstract: A sliding member for a compressor includes a base metal, a first layer and a second layer. The base metal is made of an aluminum-based metal. The first layer is formed on or over the base metal and made of a nickel-based plating layer containing at least one material of nitrogen (N), silicon (Si), titanium (Ti), chromium (Cr) and aluminum (Al) as an additive. The second layer is formed on the surface of the first layer and made of a diamond-like carbon layer containing the same additive as the additive contained in the first layer.

Abstract: A piston for an internal combustion engine includes a piston base material and a film of lubrication coating composition. The coating composition has an inner coating layer formed on a surface of the piston base material and an outer coating layer formed on a surface of the inner coating layer. Each of the inner coating layer and the outer coating layer contains at least one of a polyamide-imide resin, a polyimide resin and an epoxy resin as a binder. The inner coating layer contains 0 to 50 wt % of at least one of graphite and molybdenum disulfide as a solid lubricant, whereas the outer coating layer contains 50 to 95 wt % of at least one of graphite and molybdenum disulfide as a solid lubricant.

Abstract: A reciprocating fluid machine (2) includes pistons (32) reciprocated in respective cylinder bores (40). Each piston includes, as a lateral surface (32a) thereof, a cylindrical section (64) disposed in sliding contact with the corresponding cylinder bore with a coating layer (66) therebetween, ring groove sections (68) fitted with respective piston rings (34), and tapered sections (70) each formed between the cylindrical section and the corresponding ring groove section and inclined from the cylindrical section toward the ring groove section so as to be gradually set apart from the cylinder bore. The coating layer is also formed on each tapered section in such a manner as to be gradually set apart from the cylinder bore.

Abstract: A double-layer lubrication coating composition is made up of an upper-layer coating composition and a lower-layer coating composition. The upper-layer coating composition is made up of 50 to 70 wt % of an epoxy resin or a polyamide-imide resin, 5 to 20 wt % of boron nitride, and 15 to 30 wt % of silicone nitride or alumina. The lower-layer coating composition is made up of 50 to 70 wt % of an epoxy resin or a polyamide-imide resin, 15 to 30 wt % of polytetrafluoroethylene and 5 to 20 wt % of molybdenum disulfide and may include graphite as required.

Abstract: Piston pin for a connecting rod in a reciprocating internal combustion engine, wherein the piston pin carries at least in the area of the running surface a thermal sprayed slide layer of a metallic bearing material or slide bearing material, as well as reciprocating internal combustion engine with a connecting rod with small and with large connecting rod eye, wherein at least the running surface of one of the piston pins is formed of a thermal sprayed slide layer of a metallic bearing material, which exhibits a lower hardness than the running surface of the corresponding connecting rod eye and process for manufacturing a described piston pin with the steps of a extrusion molding or machining a piston pin preform, introduction of a recess in the area which will later become the running surface, roughening the outer surface in the area of the recess, application of a coating of a bearing material by a thermal spray process.

Abstract: A piston made of a nitride-forming base alloy for a reciprocating internal combustion engine is disclosed. The piston includes a piston upper part having a plurality of peripheral piston ring grooves, each piston ring groove having two groove flanks, one of the piston ring grooves being closest to a combustion chamber of the internal combustion engine than the remaining piston ring grooves, the groove flanks of at least the one of the piston ring grooves being hardened using a boundary layer, the piston upper part including an external surface which includes the hardened groove flanks, and a wear and correction protection layer coating at least the external surface, the wear and correction protection layer includes a nitration layer. The nitration layer is generated by converting the nitride-forming base alloy by one of plasma nitration and plasma nitro-carburization in at least one of a nitrogen atmosphere and a nitrogen-carbon atmosphere.

Abstract: A piston assembly including a piston body having a crown and a skirt, the skirt including at least a major thrust face and a minor thrust face, wherein the piston body defines a bore between the major thrust face and the minor thrust face, and a wear coating applied to the major thrust face and the minor thrust face, the wear coating having a cured thickness of at least about 30 microns.

Abstract: A downhole pump for a well has a barrel and a plunger. The barrel has a passage extending along the length of the barrel, with the passage having an inside diameter. The plunger has an outside diameter and is received by the barrel passage for relative reciprocal movement. One of the barrel or the plunger is equipped with wear rings, with a wear ring at one or at each end. The wear rings are made of a material that is harder than the material of the respective plunger or barrel. The wear rings provide protection from abrasion, particularly in a sandy well.

Abstract: A double-layer lubrication coating composition is made up of an upper-layer coating composition and a lower-layer coating composition. The upper-layer coating composition is made up of 50 to 70 wt % of an epoxy resin or a polyamide-imide resin, 5 to 20 wt % of boron nitride, and 15 to 30 wt % of silicone nitride or alumina. The lower-layer coating composition is made up of 50 to 70 wt % of an epoxy resin or a polyamide-imide resin, 15 to 30 wt % of polytetrafluoroethylene and 5 to 20 wt % of molybdenum disulfide and may include graphite as required.

Abstract: A fluid cylinder for high temperature applications is disclosed. The fluid cylinder includes an extensible member that moves between a retracted position and an extended position by forcing a fluid, such as a pneumatic fluid or a hydraulic fluid, into the cylinder. In order to seal the extensible member against an internal surface of the cylindrical housing, the extensible member includes a sealing member defining a plurality of grooves. A corresponding plurality of metallic sealing rings are placed in each of the grooves. The sealing rings include a gap that allow for thermal expansion. The sealing rings are positioned in the grooves so that the gaps on the rings are in a staggered arrangement in the axial direction. Further, a metal alloy coating may be applied to at least certain parts of the fluid cylinder. Through the above configuration, the fluid cylinder can be made without any polymeric sealing rings, composite bearings, or lubricants that may degrade during high temperature applications.

Abstract: A piston formed from an Al alloy, such as an Al—Si alloy, has wear resistant coating applied to a predetermined portion of the outer surface. The predetermined portion of the outer surface preferably includes the piston skirt. The coating includes an adhesion promoting primer layer of a silane and a polymer coating layer. The silane primer coating promotes adhesion between the Al-alloy and the polymer coating.

Abstract: A piston for an internal combustion engine, which performs a sliding reciprocating motion in a cylinder, and a method for producing the piston. The piston has a piston head and a piston skirt having at least one bearing surface. The at least one bearing surface is provided at least in part with a first overlay, and a second overlay is applied at least to parts of the first overlay. The first overlay exhibits greater wear resistance than the second overlay.

Abstract: A miniature cooling device includes numerous improvements capable of increasing the reliability and useful lifetime of the device, as well as improving electrical power to cooling power conversion efficiency. The improvements include a unitary DC motor shaft design that incorporates a unitary mass flywheel into the shaft element and provides a solid shaft cross-section for increasing magnetic flux density in the DC motor. Additional improvements include a bend resistant flexible vane in the DC motor to compression piston drive coupler, reduced dead space volume within the compression cylinder, improved heat dissipation by a cylinder head cover and an athermalized compressor design that provides uniformly efficient operation over a wide range of operating temperatures. Further improvements include fabrication and coating improvements that increase the life of compression piston and compression cylinder wear surfaces.

Abstract: A piston for an internal combustion engine, the piston having a skirt part, comprises: a resinous coating layer formed on a surface of the skirt part; and a plurality of concaves regularly arranged in the resinous coating layer. The concaves are non-coated regions in which said resinous coating layer is not formed.

Abstract: A fluid actuator having a honed metallic sleeved inner liner assembled with fitted end caps. The inner liner and end caps are wound with carbon reinforced fiber filaments in both longitudinal and hoop orientations so as to withstand increased fluid pressure over traditional metallic designs. The fluid actuator of the present invention is lightweight and had an extremely stiff piston and rod assembly, which may also be fabricated from high flexural modulus composite materials so as to allow for a very stiff, lightweight, hydraulic cylinder which is particularly resistant to column buckling at long extensions and comprises an economical, non-rebuildable design.

Abstract: The present invention intends to provide a slide member with increasing an abrasion resistance and an adherence, a friction coefficient is further decreased. A part of the base member surface of the slide member is provided with a streak so that a surface roughness thereof by a ten-point height of roughness profile is 8 to 18 ?mRz. A dry coat lubricant has polyamideimide resin, at least one kind of a layer improve agent selected from epoxysilane and epoxy resin, and at least one kind of hard particles selected from a silicon nitride and an alumina. Such construction can not only increase the abrasion resistance and the adherence of the slide member, but can decrease friction coefficient of the slide member.

Abstract: A system and method for reducing microwelding of a piston ring installed in a circumferential groove of a piston, wherein the ring has at least one piston groove engaging surface which is coated with a polyaryletherketone polymer. This composition provides critical lubrication during the piston and piston ring break-in period and prevents localized high pressure, and high temperature areas that promote microwelding.

Abstract: Pistons reciprocating in cylinders of a hydrocarbon-fueled internal combustion engine tend to trap air and unburned fuel between the top of the piston head and its enclosing cylinder wall. The circumferential side surface (or land) of the piston head above its upper piston ring groove is provided with a thin coating of porous aluminum oxide. Particles of an oxidation catalyst for the engine's fuel are electrolytically deposited in the pores of the oxide coating. During engine operation the oxide-supported catalyst particles promote combustion of the entrained fuel.

Abstract: A piston for use in an engine. The piston includes a piston head having at least one ring groove. The piston also includes a piston skirt coated with a first thickness of a bronze coating material, and a side panel adjacent the piston skirt that is coated with a second thickness of the bronze coating material. The first and second thicknesses of the bronze coating material are different. In some embodiments, the bronze coating material also includes aluminum.

Abstract: A cryogenic refrigerator and more particularly, the cryogenic refrigerator compressor assembly procedure and to a mechanism for supporting piston for use in such a cryogenic refrigerator is described. Embodiments of the present invention solve the above-mentioned drawbacks by avoiding the radial movements of the piston. The assembly procedure of a cooler compressor comprises coating at least one piston by a material, placing each piston in the cylinder, raising the temperature up until a predetermined temperature so as the piston and/or its coat expands to occupy all the cylinder, fixing each piston in the cylinder in this position until the temperature returns to ambient temperature. Another object of this invention is the cooler compressor piston spring having two flexure bearings separated by a gap connected together by a first and an outer ring.

Abstract: A system and method for reducing microwelding of a piston ring installed in a circumferential groove of a piston, wherein the ring has at least one piston groove engaging surface which is coated with a polyaryletherketone polymer. This composition provides critical lubrication during the piston and piston ring break-in period and prevents localized high pressure, and high temperature areas that promote microwelding.

Abstract: The present invention relates to a hydraulic piston and a process for its surface treatment in order to improve above all the wear resistance and corrosion resistance at the surface of the piston. As a favorable manufacturing process for the surface treatment of an above-mentioned hydraulic piston, a multistage process is disclosed which arranges a nitrocarburization with a subsequent oxidation and a following mechanical solidification of the oxidized surface for the piston. As a result, several superposed layers—layer of oxide, connecting layer, diffusion layer—develop at the piston surface which exhibit the desired qualities.

Abstract: A sliding structure for an automotive engine includes a sliding member with a sliding portion and a lubricant applied to the sliding portion so that the sliding portion can make sliding contact with a counterpart member via the lubricant. The sliding member is either of a piston ring, a piston pin, a cam lobe, a cam journal, a plain bearing, a rotary vane and a timing chain. The sliding portion has a base made of a steel or aluminum material and a hard carbon film formed on the base to coat the sliding portion. The hard carbon film has a thickness of 0.3 to 2.0 &mgr;m, a Knoop hardness of 1500 to 4500 kg/mm2, a surface roughness Ry (&mgr;m) satisfying the following equation: Ry<{(0.75−Hk/8000)×h+0.07/0.8}, where h is the thickness (&mgr;m) of the film; and Hk is the Knoop hardness (kg/mm2) of the film.

Abstract: Protective layer for piston rings in internal combustion machines, essentially consisting of chromium carbides, tungsten carbide, chromium and nickel, whereby the protective layer against wear and tear is formed of a powder mixture in which the first powder exists as agglomerated and sintered powder made out of at least the alloy components chromium carbide, chromium and nickel, which has not experienced any subsequent embrittling heat treatment such as e.g.

Abstract: A piston type compressor has a housing, a cylinder block and a piston. The cylinder block is fixed to the housing. The piston is accommodated in the cylinder block. A piston ring is provided between the cylinder block and the piston. A sealing coat is made of soft metal, and is provided between the piston ring and the piston.

Abstract: The invention relates to a piston for a diesel engine comprising a combustion cavity. The piston crown and the cavity are plasma-sprayed with a coating. The aim of the invention is to produce the coating in a cost-effective manner. To achieve this, the layer thickness of the coating is uneven, being thicker in the border region of the cavity.

Abstract: A multipiece piston comprises a steel upper part and a lower part which is screwed to the upper part and which contains the hubs. The design of the piston improves the strength of the lower part and its resistance to material defects, and reduces production cost. The lower part of the piston consists of a precipitation-hardened ferrite-pearlite steel, preferably according to EN 10267 and with added titanium. The hubs of the lower part are preferably not reinforced with bushings.

Abstract: A composite part of a clutch for use in a motor vehicle has a plastic carrier and a film of oxidized aluminum or an aluminum alloy overlying and adhering to that part of the carrier which is in sliding contact with at least one other part of the clutch. Oxidizing of the film is the result of a chemical or electrochemical treatment.

Abstract: A piston assembly for heavy duty diesel engine applications comprises a piston having pin bosses formed with pin bores for the accommodations of a wrist pin. The wrist pin is fabricated of steel and is extendable through the small end bore of a steel connecting rod and the bores of the piston body for coupling the piston body to the connecting rod. In lieu of a conventional Cu—Pb—Sn bushing usually pressed into the small end bore, a coating of manganese phosphate is applied to either the pin or small end bore of the connecting rod and pin bosses to provide the necessary tribological properties therebetween. The porous coating absorbs and entraps lubricating oil, creating a still lubricant squeeze film between the steel running surfaces under heavy load.

Abstract: Chromium nitride coating of machine components such as reciprocating pump plungers for continuous sliding contact with non-metallic packing and gasket materials greatly increases the performance life of fluid seals. In an air driven reciprocating constant pressure pump, exterior surfaces of the pump plunger are coated with chromium nitride to a thickness of seven to ten microns. The coating resists failure from repeated sliding contact against non-metallic packing and gasket materials for at least four million pump cycles, with no evidence of cracking or release of metallic particles which would embed in the packing or gasket material and score the plunger. In lower pressure pumps, interior walls of a housing against which a sliding gasket bears, when coated with chromium nitride, greatly increase the seal life of the sliding gasket.

Abstract: A reciprocating compressor includes a cylinder block, a plurality of cylinder bores extending through the cylinder block, and a plurality of pistons slidably received in the plurality of cylinder bores, respectively. The cylinder block and the pistons are each formed of an aluminum-based material, and each of the plurality of pistons has a peripheral surface thereof covered with a thermal sprayed coating which is formed of a material having a smaller coefficient of linear expansion than one of the aluminum-based material. The thermal sprayed coating covering each of the pistons has at least one slit formed thereacross in a manner such that each of the at least one slit extends from the one end of each of the pistons to the other end of the same whereby part of the peripheral surface of the piston is exposed through the at least one slit.

Abstract: A reciprocating engine having an aluminum engine block, and an aluminum piston wherein the piston's skirt has a hard anodized first layer directly on the aluminum and a composite polymer coating atop the hard anodized layer.

Abstract: A feature of the invention resides in a plating arrangement for a piston that reciprocates within a cylinder. The piston includes a generally cylindrical piston body. The piston body includes a piston head with a nickel plating and a piston skirt with a tin plating provided at the circumference of the piston body. At least one piston ring groove with a molybdenum disulfide plating is provided in the piston skirt at an upper portion of the piston body. A piston ring with a chromium and resin layer is disposed in each of the piston ring grooves. The piston body includes a piston pin hole that defines an inner diameter surface of the piston. The inner diameter surface has a molybdenum disulfide plating. The plating arrangement for the piston enhances lubrication of the piston.

Abstract: This invention discloses a "ceramic" piston and cylinder/sleeve pair for an internal combustion engine. The pair has low coefficients of thermal expansion for closer parts tolerances without danger of seizing and/or breakage/cracking from dissimilar part expansions. A piston is formed of a structural fiber reinforced ceramic matrix composite material and then a combined first erosion-resistant and self-lubricating material is applied to a surface of a skirt portion of the piston. A cylinder/sleeve is formed of a structural fiber reinforced ceramic matrix composite material and then a second combined erosion-resistant and self-lubricating material is applied to the surface of the cylinder/sleeve.

Abstract: A system for preventing microwelding of a piston ring installed in a circumferential groove of a piston, wherein the ring has at least one piston groove engaging surface which is coated with thermal set resin, polytetrafluoroethylene and molydisulfide. This composition provides critical lubrication during the piston and piston ring break-in period and prevents localized high pressure, and high temperature areas which promote microwelding.